moved ELF specific stuff to tccelf.c

1 files changed, 1844 insertions, 0 deletions

diff --git a/tccelf.c b/tccelf.c
new file mode 100644
index 0000000..cd654ce
--- /dev/null
+++ b/tccelf.c
@@ -0,0 +1,1844 @@
+/*
+ *  ELF file handling for TCC
+ * 
+ *  Copyright (c) 2001, 2002 Fabrice Bellard
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+static int put_elf_str(Section *s, const char *sym)
+{
+    int offset, len;
+    char *ptr;
+
+    len = strlen(sym) + 1;
+    offset = s->data_offset;
+    ptr = section_ptr_add(s, len);
+    memcpy(ptr, sym, len);
+    return offset;
+}
+
+/* elf symbol hashing function */
+static unsigned long elf_hash(const unsigned char *name)
+{
+    unsigned long h = 0, g;
+    
+    while (*name) {
+        h = (h << 4) + *name++;
+        g = h & 0xf0000000;
+        if (g)
+            h ^= g >> 24;
+        h &= ~g;
+    }
+    return h;
+}
+
+/* rebuild hash table of section s */
+/* NOTE: we do factorize the hash table code to go faster */
+static void rebuild_hash(Section *s, unsigned int nb_buckets)
+{
+    Elf32_Sym *sym;
+    int *ptr, *hash, nb_syms, sym_index, h;
+    char *strtab;
+
+    strtab = s->link->data;
+    nb_syms = s->data_offset / sizeof(Elf32_Sym);
+
+    s->hash->data_offset = 0;
+    ptr = section_ptr_add(s->hash, (2 + nb_buckets + nb_syms) * sizeof(int));
+    ptr[0] = nb_buckets;
+    ptr[1] = nb_syms;
+    ptr += 2;
+    hash = ptr;
+    memset(hash, 0, (nb_buckets + 1) * sizeof(int));
+    ptr += nb_buckets + 1;
+
+    sym = (Elf32_Sym *)s->data + 1;
+    for(sym_index = 1; sym_index < nb_syms; sym_index++) {
+        if (ELF32_ST_BIND(sym->st_info) != STB_LOCAL) {
+            h = elf_hash(strtab + sym->st_name) % nb_buckets;
+            *ptr = hash[h];
+            hash[h] = sym_index;
+        } else {
+            *ptr = 0;
+        }
+        ptr++;
+        sym++;
+    }
+}
+
+/* return the symbol number */
+static int put_elf_sym(Section *s, 
+                       unsigned long value, unsigned long size,
+                       int info, int other, int shndx, const char *name)
+{
+    int name_offset, sym_index;
+    int nbuckets, h;
+    Elf32_Sym *sym;
+    Section *hs;
+    
+    sym = section_ptr_add(s, sizeof(Elf32_Sym));
+    if (name)
+        name_offset = put_elf_str(s->link, name);
+    else
+        name_offset = 0;
+    /* XXX: endianness */
+    sym->st_name = name_offset;
+    sym->st_value = value;
+    sym->st_size = size;
+    sym->st_info = info;
+    sym->st_other = other;
+    sym->st_shndx = shndx;
+    sym_index = sym - (Elf32_Sym *)s->data;
+    hs = s->hash;
+    if (hs) {
+        int *ptr, *base;
+        ptr = section_ptr_add(hs, sizeof(int));
+        base = (int *)hs->data;
+        /* only add global or weak symbols */
+        if (ELF32_ST_BIND(info) != STB_LOCAL) {
+            /* add another hashing entry */
+            nbuckets = base[0];
+            h = elf_hash(name) % nbuckets;
+            *ptr = base[2 + h];
+            base[2 + h] = sym_index;
+            base[1]++;
+            /* we resize the hash table */
+            hs->nb_hashed_syms++;
+            if (hs->nb_hashed_syms > 2 * nbuckets) {
+                rebuild_hash(s, 2 * nbuckets);
+            }
+        } else {
+            *ptr = 0;
+            base[1]++;
+        }
+    }
+    return sym_index;
+}
+
+/* find global ELF symbol 'name' and return its index. Return 0 if not
+   found. */
+static int find_elf_sym(Section *s, const char *name)
+{
+    Elf32_Sym *sym;
+    Section *hs;
+    int nbuckets, sym_index, h;
+    const char *name1;
+    
+    hs = s->hash;
+    if (!hs)
+        return 0;
+    nbuckets = ((int *)hs->data)[0];
+    h = elf_hash(name) % nbuckets;
+    sym_index = ((int *)hs->data)[2 + h];
+    while (sym_index != 0) {
+        sym = &((Elf32_Sym *)s->data)[sym_index];
+        name1 = s->link->data + sym->st_name;
+        if (!strcmp(name, name1))
+            return sym_index;
+        sym_index = ((int *)hs->data)[2 + nbuckets + sym_index];
+    }
+    return 0;
+}
+
+/* return elf symbol value or error */
+static unsigned long get_elf_sym_val(const char *name)
+{
+    int sym_index;
+    Elf32_Sym *sym;
+    
+    sym_index = find_elf_sym(symtab_section, name);
+    if (!sym_index)
+        error("%s not defined", name);
+    sym = &((Elf32_Sym *)symtab_section->data)[sym_index];
+    return sym->st_value;
+}
+
+/* add an elf symbol : check if it is already defined and patch
+   it. Return symbol index. NOTE that sh_num can be SHN_UNDEF. */
+static int add_elf_sym(Section *s, unsigned long value, unsigned long size,
+                       int info, int sh_num, const char *name)
+{
+    Elf32_Sym *esym;
+    int sym_bind, sym_index, sym_type, esym_bind;
+
+    sym_bind = ELF32_ST_BIND(info);
+    sym_type = ELF32_ST_TYPE(info);
+        
+    if (sym_bind != STB_LOCAL) {
+        /* we search global or weak symbols */
+        sym_index = find_elf_sym(s, name);
+        if (!sym_index)
+            goto do_def;
+        esym = &((Elf32_Sym *)s->data)[sym_index];
+        if (esym->st_shndx != SHN_UNDEF) {
+            esym_bind = ELF32_ST_BIND(esym->st_info);
+            if (sh_num == SHN_UNDEF) {
+                /* ignore adding of undefined symbol if the
+                   corresponding symbol is already defined */
+            } else if (sym_bind == STB_GLOBAL && esym_bind == STB_WEAK) {
+                /* global overrides weak, so patch */
+                goto do_patch;
+            } else if (sym_bind == STB_WEAK && esym_bind == STB_GLOBAL) {
+                /* weak is ignored if already global */
+            } else {
+#if 0
+                printf("new_bind=%d new_shndx=%d last_bind=%d old_shndx=%d\n",
+                       sym_bind, sh_num, esym_bind, esym->st_shndx);
+#endif
+                /* NOTE: we accept that two DLL define the same symbol */
+                if (s != dynsymtab_section)
+                    error("'%s' defined twice", name);
+            }
+        } else {
+        do_patch:
+            esym->st_info = ELF32_ST_INFO(sym_bind, sym_type);
+            esym->st_shndx = sh_num;
+            esym->st_value = value;
+            esym->st_size = size;
+        }
+    } else {
+    do_def:
+        sym_index = put_elf_sym(s, value, size, 
+                                ELF32_ST_INFO(sym_bind, sym_type), 0, 
+                                sh_num, name);
+    }
+    return sym_index;
+}
+
+/* put relocation */
+static void put_elf_reloc(Section *symtab, Section *s, unsigned long offset,
+                          int type, int symbol)
+{
+    char buf[256];
+    Section *sr;
+    Elf32_Rel *rel;
+
+    sr = s->reloc;
+    if (!sr) {
+        /* if no relocation section, create it */
+        snprintf(buf, sizeof(buf), ".rel%s", s->name);
+        /* if the symtab is allocated, then we consider the relocation
+           are also */
+        sr = new_section(buf, SHT_REL, symtab->sh_flags);
+        sr->sh_entsize = sizeof(Elf32_Rel);
+        sr->link = symtab;
+        sr->sh_info = s->sh_num;
+        s->reloc = sr;
+    }
+    rel = section_ptr_add(sr, sizeof(Elf32_Rel));
+    rel->r_offset = offset;
+    rel->r_info = ELF32_R_INFO(symbol, type);
+}
+
+/* put stab debug information */
+
+typedef struct {
+    unsigned long n_strx;         /* index into string table of name */
+    unsigned char n_type;         /* type of symbol */
+    unsigned char n_other;        /* misc info (usually empty) */
+    unsigned short n_desc;        /* description field */
+    unsigned long n_value;        /* value of symbol */
+} Stab_Sym;
+
+static void put_stabs(const char *str, int type, int other, int desc, 
+                      unsigned long value)
+{
+    Stab_Sym *sym;
+
+    sym = section_ptr_add(stab_section, sizeof(Stab_Sym));
+    if (str) {
+        sym->n_strx = put_elf_str(stabstr_section, str);
+    } else {
+        sym->n_strx = 0;
+    }
+    sym->n_type = type;
+    sym->n_other = other;
+    sym->n_desc = desc;
+    sym->n_value = value;
+}
+
+static void put_stabs_r(const char *str, int type, int other, int desc, 
+                        unsigned long value, Section *sec, int sym_index)
+{
+    put_stabs(str, type, other, desc, value);
+    put_elf_reloc(symtab_section, stab_section, 
+                  stab_section->data_offset - sizeof(unsigned long),
+                  R_DATA_32, sym_index);
+}
+
+static void put_stabn(int type, int other, int desc, int value)
+{
+    put_stabs(NULL, type, other, desc, value);
+}
+
+static void put_stabd(int type, int other, int desc)
+{
+    put_stabs(NULL, type, other, desc, 0);
+}
+
+/* In an ELF file symbol table, the local symbols must appear below
+   the global and weak ones. Since TCC cannot sort it while generating
+   the code, we must do it after. All the relocation tables are also
+   modified to take into account the symbol table sorting */
+static void sort_syms(Section *s)
+{
+    int *old_to_new_syms;
+    Elf32_Sym *new_syms;
+    int nb_syms, i;
+    Elf32_Sym *p, *q;
+    Elf32_Rel *rel, *rel_end;
+    Section *sr;
+    int type, sym_index;
+
+    nb_syms = s->data_offset / sizeof(Elf32_Sym);
+    new_syms = tcc_malloc(nb_syms * sizeof(Elf32_Sym));
+    old_to_new_syms = tcc_malloc(nb_syms * sizeof(int));
+
+    /* first pass for local symbols */
+    p = (Elf32_Sym *)s->data;
+    q = new_syms;
+    for(i = 0; i < nb_syms; i++) {
+        if (ELF32_ST_BIND(p->st_info) == STB_LOCAL) {
+            old_to_new_syms[i] = q - new_syms;
+            *q++ = *p;
+        }
+        p++;
+    }
+    /* save the number of local symbols in section header */
+    s->sh_info = q - new_syms;
+
+    /* then second pass for non local symbols */
+    p = (Elf32_Sym *)s->data;
+    for(i = 0; i < nb_syms; i++) {
+        if (ELF32_ST_BIND(p->st_info) != STB_LOCAL) {
+            old_to_new_syms[i] = q - new_syms;
+            *q++ = *p;
+        }
+        p++;
+    }
+    
+    /* we copy the new symbols to the old */
+    memcpy(s->data, new_syms, nb_syms * sizeof(Elf32_Sym));
+    tcc_free(new_syms);
+
+    /* now we modify all the relocations */
+    for(i = 1; i < nb_sections; i++) {
+        sr = sections[i];
+        if (sr->sh_type == SHT_REL && sr->link == s) {
+            rel_end = (Elf32_Rel *)(sr->data + sr->data_offset);
+            for(rel = (Elf32_Rel *)sr->data;
+                rel < rel_end;
+                rel++) {
+                sym_index = ELF32_R_SYM(rel->r_info);
+                type = ELF32_R_TYPE(rel->r_info);
+                sym_index = old_to_new_syms[sym_index];
+                rel->r_info = ELF32_R_INFO(sym_index, type);
+            }
+        }
+    }
+    
+    tcc_free(old_to_new_syms);
+}
+
+/* relocate common symbols in the .bss section */
+static void relocate_common_syms(void)
+{
+    Elf32_Sym *sym, *sym_end;
+    unsigned long offset, align;
+    
+    sym_end = (Elf32_Sym *)(symtab_section->data + symtab_section->data_offset);
+    for(sym = (Elf32_Sym *)symtab_section->data + 1; 
+        sym < sym_end;
+        sym++) {
+        if (sym->st_shndx == SHN_COMMON) {
+            /* align symbol */
+            align = sym->st_value;
+            offset = bss_section->data_offset;
+            offset = (offset + align - 1) & -align;
+            sym->st_value = offset;
+            sym->st_shndx = bss_section->sh_num;
+            offset += sym->st_size;
+            bss_section->data_offset = offset;
+        }
+    }
+}
+
+static void *resolve_sym(const char *sym)
+{
+    return dlsym(NULL, sym);
+}
+
+/* relocate symbol table, resolve undefined symbols if do_resolve is
+   true and output error if undefined symbol. */
+static void relocate_syms(int do_resolve)
+{
+    Elf32_Sym *sym, *esym, *sym_end;
+    int sym_bind, sh_num, sym_index;
+    const char *name;
+    unsigned long addr;
+
+    sym_end = (Elf32_Sym *)(symtab_section->data + symtab_section->data_offset);
+    for(sym = (Elf32_Sym *)symtab_section->data + 1; 
+        sym < sym_end;
+        sym++) {
+        sh_num = sym->st_shndx;
+        if (sh_num == SHN_UNDEF) {
+            name = strtab_section->data + sym->st_name;
+            if (do_resolve) {
+                name = symtab_section->link->data + sym->st_name;
+                addr = (unsigned long)resolve_sym(name);
+                if (addr) {
+                    sym->st_value = addr;
+                    goto found;
+                }
+            } else if (dynsym) {
+                /* if dynamic symbol exist, then use it */
+                sym_index = find_elf_sym(dynsym, name);
+                if (sym_index) {
+                    esym = &((Elf32_Sym *)dynsym->data)[sym_index];
+                    sym->st_value = esym->st_value;
+                    goto found;
+                }
+            }
+            /* XXX: _fp_hw seems to be part of the ABI, so we ignore
+               it */
+            if (!strcmp(name, "_fp_hw"))
+                goto found;
+            /* only weak symbols are accepted to be undefined. Their
+               value is zero */
+            sym_bind = ELF32_ST_BIND(sym->st_info);
+            if (sym_bind == STB_WEAK) {
+                sym->st_value = 0;
+            } else {
+                error("undefined symbol '%s'", name);
+            }
+        } else if (sh_num < SHN_LORESERVE) {
+            /* add section base */
+            sym->st_value += sections[sym->st_shndx]->sh_addr;
+        }
+    found: ;
+    }
+}
+
+/* relocate a given section (CPU dependant) */
+static void relocate_section(TCCState *s1, Section *s)
+{
+    Section *sr;
+    Elf32_Rel *rel, *rel_end, *qrel;
+    Elf32_Sym *sym;
+    int type, sym_index, esym_index;
+    unsigned char *ptr;
+    unsigned long val, addr;
+
+    sr = s->reloc;
+    rel_end = (Elf32_Rel *)(sr->data + sr->data_offset);
+    qrel = (Elf32_Rel *)sr->data;
+    for(rel = qrel;
+        rel < rel_end;
+        rel++) {
+        ptr = s->data + rel->r_offset;
+
+        sym_index = ELF32_R_SYM(rel->r_info);
+        sym = &((Elf32_Sym *)symtab_section->data)[sym_index];
+        val = sym->st_value;
+        type = ELF32_R_TYPE(rel->r_info);
+        addr = s->sh_addr + rel->r_offset;
+
+        /* CPU specific */
+        switch(type) {
+        case R_386_32:
+            if (s1->output_type == TCC_OUTPUT_DLL) {
+                esym_index = symtab_to_dynsym[sym_index];
+                qrel->r_offset = rel->r_offset;
+                if (esym_index) {
+                    qrel->r_info = ELF32_R_INFO(esym_index, R_386_32);
+                    qrel++;
+                    break;
+                } else {
+                    qrel->r_info = ELF32_R_INFO(0, R_386_RELATIVE);
+                    qrel++;
+                }
+            }
+            *(int *)ptr += val;
+            break;
+        case R_386_PC32:
+            if (s1->output_type == TCC_OUTPUT_DLL) {
+                /* DLL relocation */
+                esym_index = symtab_to_dynsym[sym_index];
+                if (esym_index) {
+                    qrel->r_offset = rel->r_offset;
+                    qrel->r_info = ELF32_R_INFO(esym_index, R_386_PC32);
+                    qrel++;
+                    break;
+                }
+            }
+            *(int *)ptr += val - addr;
+            break;
+        case R_386_PLT32:
+            *(int *)ptr += val - addr;
+            break;
+        case R_386_GLOB_DAT:
+        case R_386_JMP_SLOT:
+            *(int *)ptr = val;
+            break;
+        case R_386_GOTPC:
+            *(int *)ptr += got->sh_addr - addr;
+            break;
+        case R_386_GOTOFF:
+            *(int *)ptr += val - got->sh_addr;
+            break;
+        case R_386_GOT32:
+            /* we load the got offset */
+            *(int *)ptr += got_offsets[sym_index];
+            break;
+        }
+    }
+    /* if the relocation is allocated, we change its symbol table */
+    if (sr->sh_flags & SHF_ALLOC)
+        sr->link = dynsym;
+}
+
+/* relocate relocation table in 'sr' */
+static void relocate_rel(Section *sr)
+{
+    Section *s;
+    Elf32_Rel *rel, *rel_end;
+    
+    s = sections[sr->sh_info];
+    rel_end = (Elf32_Rel *)(sr->data + sr->data_offset);
+    for(rel = (Elf32_Rel *)sr->data;
+        rel < rel_end;
+        rel++) {
+        rel->r_offset += s->sh_addr;
+    }
+}
+
+/* count the number of dynamic relocations so that we can reserve
+   their space */
+static int prepare_dynamic_rel(Section *sr)
+{
+    Elf32_Rel *rel, *rel_end;
+    int sym_index, esym_index, type, count;
+
+    count = 0;
+    rel_end = (Elf32_Rel *)(sr->data + sr->data_offset);
+    for(rel = (Elf32_Rel *)sr->data; rel < rel_end; rel++) {
+        sym_index = ELF32_R_SYM(rel->r_info);
+        type = ELF32_R_TYPE(rel->r_info);
+        switch(type) {
+        case R_386_32:
+            count++;
+            break;
+        case R_386_PC32:
+            esym_index = symtab_to_dynsym[sym_index];
+            if (esym_index)
+                count++;
+            break;
+        default:
+            break;
+        }
+    }
+    if (count) {
+        /* allocate the section */
+        sr->sh_flags |= SHF_ALLOC;
+        sr->sh_size = count * sizeof(Elf32_Rel);
+    }
+    return count;
+}
+
+static void put_got_offset(int index, unsigned long val)
+{
+    int n;
+    unsigned long *tab;
+
+    if (index >= nb_got_offsets) {
+        /* find immediately bigger power of 2 and reallocate array */
+        n = 1;
+        while (index >= n)
+            n *= 2;
+        tab = tcc_realloc(got_offsets, n * sizeof(unsigned long));
+        if (!tab)
+            error("memory full");
+        got_offsets = tab;
+        memset(got_offsets + nb_got_offsets, 0,
+               (n - nb_got_offsets) * sizeof(unsigned long));
+        nb_got_offsets = n;
+    }
+    got_offsets[index] = val;
+}
+
+/* XXX: suppress that */
+static void put32(unsigned char *p, unsigned int val)
+{
+    p[0] = val;
+    p[1] = val >> 8;
+    p[2] = val >> 16;
+    p[3] = val >> 24;
+}
+
+static void build_got(void)
+{
+    unsigned char *ptr;
+
+    /* if no got, then create it */
+    got = new_section(".got", SHT_PROGBITS, SHF_ALLOC | SHF_WRITE);
+    got->sh_entsize = 4;
+    add_elf_sym(symtab_section, 0, 4, ELF32_ST_INFO(STB_GLOBAL, STT_OBJECT), 
+                got->sh_num, "_GLOBAL_OFFSET_TABLE_");
+    ptr = section_ptr_add(got, 3 * sizeof(int));
+    /* keep space for _DYNAMIC pointer, if present */
+    put32(ptr, 0);
+    /* two dummy got entries */
+    put32(ptr + 4, 0);
+    put32(ptr + 8, 0);
+}
+
+/* put a got entry corresponding to a symbol in symtab_section. 'size'
+   and 'info' can be modifed if more precise info comes from the DLL */
+static void put_got_entry(int reloc_type, unsigned long size, int info, 
+                          int sym_index)
+{
+    int index;
+    const char *name;
+    Elf32_Sym *sym;
+    unsigned long offset;
+    int *ptr;
+
+    if (!got)
+        build_got();
+
+    /* if a got entry already exists for that symbol, no need to add one */
+    if (sym_index < nb_got_offsets &&
+        got_offsets[sym_index] != 0)
+        return;
+    
+    put_got_offset(sym_index, got->data_offset);
+
+    if (dynsym) {
+        sym = &((Elf32_Sym *)symtab_section->data)[sym_index];
+        name = symtab_section->link->data + sym->st_name;
+        offset = sym->st_value;
+        /* NOTE: we put temporarily the got offset */
+        if (reloc_type == R_386_JMP_SLOT) {
+            nb_plt_entries++;
+            offset = got->data_offset;
+        }
+        index = put_elf_sym(dynsym, offset, 
+                            size, info, 0, sym->st_shndx, name);
+        /* put a got entry */
+        put_elf_reloc(dynsym, got, 
+                      got->data_offset, 
+                      reloc_type, index);
+    }
+    ptr = section_ptr_add(got, sizeof(int));
+    *ptr = 0;
+}
+
+/* build GOT and PLT entries */
+static void build_got_entries(void)
+{
+    Section *s, *symtab;
+    Elf32_Rel *rel, *rel_end;
+    Elf32_Sym *sym;
+    int i, type, reloc_type, sym_index;
+
+    for(i = 1; i < nb_sections; i++) {
+        s = sections[i];
+        if (s->sh_type != SHT_REL)
+            continue;
+        /* no need to handle got relocations */
+        if (s->link != symtab_section)
+            continue;
+        symtab = s->link;
+        rel_end = (Elf32_Rel *)(s->data + s->data_offset);
+        for(rel = (Elf32_Rel *)s->data;
+            rel < rel_end;
+            rel++) {
+            type = ELF32_R_TYPE(rel->r_info);
+            switch(type) {
+            case R_386_GOT32:
+            case R_386_GOTOFF:
+            case R_386_GOTPC:
+            case R_386_PLT32:
+                if (!got)
+                    build_got();
+                if (type == R_386_GOT32 || type == R_386_PLT32) {
+                    sym_index = ELF32_R_SYM(rel->r_info);
+                    sym = &((Elf32_Sym *)symtab_section->data)[sym_index];
+                    /* look at the symbol got offset. If none, then add one */
+                    if (type == R_386_GOT32)
+                        reloc_type = R_386_GLOB_DAT;
+                    else
+                        reloc_type = R_386_JMP_SLOT;
+                    put_got_entry(reloc_type, sym->st_size, sym->st_info, 
+                                  sym_index);
+                }
+                break;
+            default:
+                break;
+            }
+        }
+    }
+}
+
+static Section *new_symtab(const char *symtab_name, int sh_type, int sh_flags,
+                           const char *strtab_name, 
+                           const char *hash_name, int hash_sh_flags)
+{
+    Section *symtab, *strtab, *hash;
+    int *ptr, nb_buckets;
+
+    symtab = new_section(symtab_name, sh_type, sh_flags);
+    symtab->sh_entsize = sizeof(Elf32_Sym);
+    strtab = new_section(strtab_name, SHT_STRTAB, sh_flags);
+    put_elf_str(strtab, "");
+    symtab->link = strtab;
+    put_elf_sym(symtab, 0, 0, 0, 0, 0, NULL);
+    
+    nb_buckets = 1;
+
+    hash = new_section(hash_name, SHT_HASH, hash_sh_flags);
+    hash->sh_entsize = sizeof(int);
+    symtab->hash = hash;
+    hash->link = symtab;
+
+    ptr = section_ptr_add(hash, (2 + nb_buckets + 1) * sizeof(int));
+    ptr[0] = nb_buckets;
+    ptr[1] = 1;
+    memset(ptr + 2, 0, (nb_buckets + 1) * sizeof(int));
+    return symtab;
+}
+
+/* put dynamic tag */
+static void put_dt(Section *dynamic, int dt, unsigned long val)
+{
+    Elf32_Dyn *dyn;
+    dyn = section_ptr_add(dynamic, sizeof(Elf32_Dyn));
+    dyn->d_tag = dt;
+    dyn->d_un.d_val = val;
+}
+
+/* add tcc runtime libraries */
+static void tcc_add_runtime(TCCState *s1)
+{
+    char buf[1024];
+    int i;
+    Section *s;
+
+    snprintf(buf, sizeof(buf), "%s/%s", tcc_lib_path, "libtcc1.o");
+    tcc_add_file(s1, buf);
+#ifdef CONFIG_TCC_BCHECK
+    if (do_bounds_check) {
+        unsigned long *ptr;
+        Section *init_section;
+        unsigned char *pinit;
+        int sym_index;
+
+        /* XXX: add an object file to do that */
+        ptr = section_ptr_add(bounds_section, sizeof(unsigned long));
+        *ptr = 0;
+        add_elf_sym(symtab_section, 0, 0, 
+                    ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
+                    bounds_section->sh_num, "__bounds_start");
+        /* add bound check code */
+        snprintf(buf, sizeof(buf), "%s/%s", tcc_lib_path, "bcheck.o");
+        tcc_add_file(s1, buf);
+#ifdef TCC_TARGET_I386
+        if (s1->output_type != TCC_OUTPUT_MEMORY) {
+            /* add 'call __bound_init()' in .init section */
+            init_section = find_section(".init");
+            pinit = section_ptr_add(init_section, 5);
+            pinit[0] = 0xe8;
+            put32(pinit + 1, -4);
+            sym_index = find_elf_sym(symtab_section, "__bound_init");
+            put_elf_reloc(symtab_section, init_section, 
+                          init_section->data_offset - 4, R_386_PC32, sym_index);
+        }
+#endif
+    }
+#endif
+    /* add libc if not memory output */
+    if (s1->output_type != TCC_OUTPUT_MEMORY) {
+        tcc_add_library(s1, "c");
+        tcc_add_file(s1, CONFIG_TCC_CRT_PREFIX "/crtn.o");
+    }
+    /* add various standard linker symbols */
+    add_elf_sym(symtab_section, 
+                text_section->data_offset, 0,
+                ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
+                text_section->sh_num, "_etext");
+    add_elf_sym(symtab_section, 
+                data_section->data_offset, 0,
+                ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
+                data_section->sh_num, "_edata");
+    add_elf_sym(symtab_section, 
+                bss_section->data_offset, 0,
+                ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
+                bss_section->sh_num, "_end");
+    /* add start and stop symbols for sections whose name can be
+       expressed in C */
+    for(i = 1; i < nb_sections; i++) {
+        s = sections[i];
+        if (s->sh_type == SHT_PROGBITS &&
+            (s->sh_flags & SHF_ALLOC)) {
+            const char *p;
+            int ch;
+
+            /* check if section name can be expressed in C */
+            p = s->name;
+            for(;;) {
+                ch = *p;
+                if (!ch)
+                    break;
+                if (!isid(ch) && !isnum(ch))
+                    goto next_sec;
+                p++;
+            }
+            snprintf(buf, sizeof(buf), "__start_%s", s->name);
+            add_elf_sym(symtab_section, 
+                        0, 0,
+                        ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
+                        s->sh_num, buf);
+            snprintf(buf, sizeof(buf), "__stop_%s", s->name);
+            add_elf_sym(symtab_section,
+                        s->data_offset, 0,
+                        ELF32_ST_INFO(STB_GLOBAL, STT_NOTYPE),
+                        s->sh_num, buf);
+        }
+    next_sec: ;
+    }
+}
+
+/* name of ELF interpreter */
+static char elf_interp[] = "/lib/ld-linux.so.2";
+
+#define ELF_START_ADDR 0x08048000
+#define ELF_PAGE_SIZE  0x1000
+
+/* output an ELF file */
+/* XXX: suppress unneeded sections */
+int tcc_output_file(TCCState *s1, const char *filename)
+{
+    Elf32_Ehdr ehdr;
+    FILE *f;
+    int fd, mode;
+    int *section_order;
+    int shnum, i, phnum, file_offset, offset, size, j, tmp, sh_order_index, k;
+    unsigned long addr;
+    Section *strsec, *s;
+    Elf32_Shdr shdr, *sh;
+    Elf32_Phdr *phdr, *ph;
+    Section *interp, *plt, *dynamic, *dynstr;
+    unsigned long saved_dynamic_data_offset;
+    Elf32_Sym *sym;
+    int type, file_type;
+    unsigned long rel_addr, rel_size;
+    
+    file_type = s1->output_type;
+
+    if (file_type != TCC_OUTPUT_OBJ)
+        tcc_add_runtime(s1);
+
+    interp = NULL;
+    dynamic = NULL;
+    dynsym = NULL;
+    got = NULL;
+    nb_plt_entries = 0;
+    plt = NULL; /* avoid warning */
+    dynstr = NULL; /* avoid warning */
+    saved_dynamic_data_offset = 0; /* avoid warning */
+
+    if (file_type != TCC_OUTPUT_OBJ) {
+
+        relocate_common_syms();
+
+        if (!static_link) {
+            const char *name;
+            int sym_index, index;
+            Elf32_Sym *esym, *sym_end;
+            
+            if (file_type == TCC_OUTPUT_EXE) {
+                char *ptr;
+                /* add interpreter section only if executable */
+                interp = new_section(".interp", SHT_PROGBITS, SHF_ALLOC);
+                interp->sh_addralign = 1;
+                ptr = section_ptr_add(interp, sizeof(elf_interp));
+                strcpy(ptr, elf_interp);
+            }
+        
+            /* add dynamic symbol table */
+            dynsym = new_symtab(".dynsym", SHT_DYNSYM, SHF_ALLOC,
+                                ".dynstr", 
+                                ".hash", SHF_ALLOC);
+            dynstr = dynsym->link;
+            
+            /* add dynamic section */
+            dynamic = new_section(".dynamic", SHT_DYNAMIC, 
+                                  SHF_ALLOC | SHF_WRITE);
+            dynamic->link = dynstr;
+            dynamic->sh_entsize = sizeof(Elf32_Dyn);
+        
+            /* add PLT */
+            plt = new_section(".plt", SHT_PROGBITS, SHF_ALLOC | SHF_EXECINSTR);
+            plt->sh_entsize = 4;
+
+            build_got();
+
+            /* scan for undefined symbols and see if they are in the
+               dynamic symbols. If a symbol STT_FUNC is found, then we
+               add it in the PLT. If a symbol STT_OBJECT is found, we
+               add it in the .bss section with a suitable relocation */
+            sym_end = (Elf32_Sym *)(symtab_section->data + 
+                                    symtab_section->data_offset);
+            if (file_type == TCC_OUTPUT_EXE) {
+                for(sym = (Elf32_Sym *)symtab_section->data + 1; 
+                    sym < sym_end;
+                    sym++) {
+                    if (sym->st_shndx == SHN_UNDEF) {
+                        name = symtab_section->link->data + sym->st_name;
+                        sym_index = find_elf_sym(dynsymtab_section, name);
+                        if (sym_index) {
+                            esym = &((Elf32_Sym *)dynsymtab_section->data)[sym_index];
+                            type = ELF32_ST_TYPE(esym->st_info);
+                            if (type == STT_FUNC) {
+                                put_got_entry(R_386_JMP_SLOT, esym->st_size, 
+                                              esym->st_info, 
+                                              sym - (Elf32_Sym *)symtab_section->data);
+                            } else if (type == STT_OBJECT) {
+                                unsigned long offset;
+                                offset = bss_section->data_offset;
+                                /* XXX: which alignment ? */
+                                offset = (offset + 8 - 1) & -8;
+                                index = put_elf_sym(dynsym, offset, esym->st_size, 
+                                                    esym->st_info, 0, 
+                                                    bss_section->sh_num, name);
+                                put_elf_reloc(dynsym, bss_section, 
+                                              offset, R_386_COPY, index);
+                                offset += esym->st_size;
+                                bss_section->data_offset = offset;
+                            }
+                        } else {
+                                /* STB_WEAK undefined symbols are accepted */
+                                /* XXX: _fp_hw seems to be part of the ABI, so we ignore
+                                   it */
+                            if (ELF32_ST_BIND(sym->st_info) == STB_WEAK ||
+                                !strcmp(name, "_fp_hw")) {
+                            } else {
+                                error("undefined symbol '%s'", name);
+                            }
+                        }
+                    }
+                }
+            
+                /* now look at unresolved dynamic symbols and export
+                   corresponding symbol */
+                sym_end = (Elf32_Sym *)(dynsymtab_section->data + 
+                                        dynsymtab_section->data_offset);
+                for(esym = (Elf32_Sym *)dynsymtab_section->data + 1; 
+                    esym < sym_end;
+                    esym++) {
+                    if (esym->st_shndx == SHN_UNDEF) {
+                        name = dynsymtab_section->link->data + esym->st_name;
+                        sym_index = find_elf_sym(symtab_section, name);
+                        if (sym_index) {
+                            sym = &((Elf32_Sym *)symtab_section->data)[sym_index];
+                            put_elf_sym(dynsym, sym->st_value, sym->st_size, 
+                                        sym->st_info, 0, 
+                                        sym->st_shndx, name);
+                        } else {
+                            if (ELF32_ST_BIND(esym->st_info) == STB_WEAK) {
+                                /* weak symbols can stay undefined */
+                            } else {
+                                warning("undefined dynamic symbol '%s'", name);
+                            }
+                        }
+                    }
+                }
+            } else {
+                int nb_syms;
+                /* shared library case : we simply export all the global symbols */
+                nb_syms = symtab_section->data_offset / sizeof(Elf32_Sym);
+                symtab_to_dynsym = tcc_mallocz(sizeof(int) * nb_syms);
+                for(sym = (Elf32_Sym *)symtab_section->data + 1; 
+                    sym < sym_end;
+                    sym++) {
+                    if (ELF32_ST_BIND(sym->st_info) != STB_LOCAL) {
+                        name = symtab_section->link->data + sym->st_name;
+                        index = put_elf_sym(dynsym, sym->st_value, sym->st_size, 
+                                            sym->st_info, 0, 
+                                            sym->st_shndx, name);
+                        symtab_to_dynsym[sym - (Elf32_Sym *)symtab_section->data] = 
+                            index;
+                    }
+                }
+            }
+
+            build_got_entries();
+        
+            /* update PLT/GOT sizes so that we can allocate their space */
+            plt->data_offset += 16 * (nb_plt_entries + 1);
+
+            /* add a list of needed dlls */
+            for(i = 0; i < nb_loaded_dlls; i++) {
+                DLLReference *dllref = loaded_dlls[i];
+                if (dllref->level == 0)
+                    put_dt(dynamic, DT_NEEDED, put_elf_str(dynstr, dllref->name));
+            }
+            /* XXX: currently, since we do not handle PIC code, we
+               must relocate the readonly segments */
+            if (file_type == TCC_OUTPUT_DLL)
+                put_dt(dynamic, DT_TEXTREL, 0);
+
+            /* add necessary space for other entries */
+            saved_dynamic_data_offset = dynamic->data_offset;
+            dynamic->data_offset += 8 * 9;
+        } else {
+            /* still need to build got entries in case of static link */
+            build_got_entries();
+        }
+    }
+
+    memset(&ehdr, 0, sizeof(ehdr));
+
+    /* we add a section for symbols */
+    strsec = new_section(".shstrtab", SHT_STRTAB, 0);
+    put_elf_str(strsec, "");
+    
+    /* compute number of sections */
+    shnum = nb_sections;
+
+    /* this array is used to reorder sections in the output file */
+    section_order = tcc_malloc(sizeof(int) * shnum);
+    section_order[0] = 0;
+    sh_order_index = 1;
+    
+    /* compute number of program headers */
+    switch(file_type) {
+    default:
+    case TCC_OUTPUT_OBJ:
+        phnum = 0;
+        break;
+    case TCC_OUTPUT_EXE:
+        if (!static_link)
+            phnum = 4;
+        else
+            phnum = 2;
+        break;
+    case TCC_OUTPUT_DLL:
+        phnum = 3;
+        break;
+    }
+
+    /* allocate strings for section names and decide if an unallocated
+       section should be output */
+    /* NOTE: the strsec section comes last, so its size is also
+       correct ! */
+    for(i = 1; i < nb_sections; i++) {
+        s = sections[i];
+        s->sh_name = put_elf_str(strsec, s->name);
+        /* when generating a DLL, we include relocations but we may
+           patch them */
+        if (file_type == TCC_OUTPUT_DLL && 
+            s->sh_type == SHT_REL && 
+            !(s->sh_flags & SHF_ALLOC)) {
+            prepare_dynamic_rel(s);
+        } else if (do_debug || 
+            file_type == TCC_OUTPUT_OBJ || 
+            (s->sh_flags & SHF_ALLOC) ||
+            i == (nb_sections - 1)) {
+            /* we output all sections if debug or object file */
+            s->sh_size = s->data_offset;
+        }
+    }
+
+    /* allocate program segment headers */
+    phdr = tcc_mallocz(phnum * sizeof(Elf32_Phdr));
+        
+    file_offset = sizeof(Elf32_Ehdr) + phnum * sizeof(Elf32_Phdr);
+    if (phnum > 0) {
+        /* compute section to program header mapping */
+        if (file_type == TCC_OUTPUT_DLL)
+            addr = 0;
+        else
+            addr = ELF_START_ADDR;
+
+        /* dynamic relocation table information, for .dynamic section */
+        rel_size = 0;
+        rel_addr = 0;
+
+        /* compute address after headers */
+        addr += (file_offset & (ELF_PAGE_SIZE - 1));
+        
+        /* leave one program header for the program interpreter */
+        ph = &phdr[0];
+        if (interp)
+            ph++;
+
+        for(j = 0; j < 2; j++) {
+            ph->p_type = PT_LOAD;
+            if (j == 0)
+                ph->p_flags = PF_R | PF_X;
+            else
+                ph->p_flags = PF_R | PF_W;
+            ph->p_align = ELF_PAGE_SIZE;
+            
+            /* we do the following ordering: interp, symbol tables,
+               relocations, progbits, nobits */
+            /* XXX: do faster and simpler sorting */
+            for(k = 0; k < 5; k++) {
+                for(i = 1; i < nb_sections; i++) {
+                    s = sections[i];
+                    /* compute if section should be included */
+                    if (j == 0) {
+                        if ((s->sh_flags & (SHF_ALLOC | SHF_WRITE)) != 
+                            SHF_ALLOC)
+                            continue;
+                    } else {
+                        if ((s->sh_flags & (SHF_ALLOC | SHF_WRITE)) != 
+                            (SHF_ALLOC | SHF_WRITE))
+                            continue;
+                    }
+                    if (s == interp) {
+                        if (k != 0)
+                            continue;
+                    } else if (s->sh_type == SHT_DYNSYM ||
+                               s->sh_type == SHT_STRTAB ||
+                               s->sh_type == SHT_HASH) {
+                        if (k != 1)
+                            continue;
+                    } else if (s->sh_type == SHT_REL) {
+                        if (k != 2)
+                            continue;
+                    } else if (s->sh_type == SHT_NOBITS) {
+                        if (k != 4)
+                            continue;
+                    } else {
+                        if (k != 3)
+                            continue;
+                    }
+                    section_order[sh_order_index++] = i;
+
+                    /* section matches: we align it and add its size */
+                    tmp = file_offset;
+                    file_offset = (file_offset + s->sh_addralign - 1) & 
+                        ~(s->sh_addralign - 1);
+                    s->sh_offset = file_offset;
+                    addr += file_offset - tmp;
+                    s->sh_addr = addr;
+                    
+                    /* update program header infos */
+                    if (ph->p_offset == 0) {
+                        ph->p_offset = file_offset;
+                        ph->p_vaddr = addr;
+                        ph->p_paddr = ph->p_vaddr;
+                    }
+                    /* update dynamic relocation infos */
+                    if (s->sh_type == SHT_REL) {
+                        if (rel_size == 0)
+                            rel_addr = addr;
+                        rel_size += s->sh_size;
+                    }
+                    addr += s->sh_size;
+                    if (s->sh_type != SHT_NOBITS)
+                        file_offset += s->sh_size;
+                }
+            }
+            ph->p_filesz = file_offset - ph->p_offset;
+            ph->p_memsz = addr - ph->p_vaddr;
+            ph++;
+        }
+
+        /* if interpreter, then add corresponing program header */
+        if (interp) {
+            ph = &phdr[0];
+            
+            ph->p_type = PT_INTERP;
+            ph->p_offset = interp->sh_offset;
+            ph->p_vaddr = interp->sh_addr;
+            ph->p_paddr = ph->p_vaddr;
+            ph->p_filesz = interp->sh_size;
+            ph->p_memsz = interp->sh_size;
+            ph->p_flags = PF_R;
+            ph->p_align = interp->sh_addralign;
+        }
+        
+        /* if dynamic section, then add corresponing program header */
+        if (dynamic) {
+            int plt_offset;
+            unsigned char *p;
+            Elf32_Sym *sym_end;
+
+            ph = &phdr[phnum - 1];
+            
+            ph->p_type = PT_DYNAMIC;
+            ph->p_offset = dynamic->sh_offset;
+            ph->p_vaddr = dynamic->sh_addr;
+            ph->p_paddr = ph->p_vaddr;
+            ph->p_filesz = dynamic->sh_size;
+            ph->p_memsz = dynamic->sh_size;
+            ph->p_flags = PF_R | PF_W;
+            ph->p_align = dynamic->sh_addralign;
+
+            /* put GOT dynamic section address */
+            put32(got->data, dynamic->sh_addr);
+
+            /* compute the PLT */
+            plt->data_offset = 0;
+            
+            /* first plt entry */
+            p = section_ptr_add(plt, 16);
+            p[0] = 0xff; /* pushl got + 4 */
+            p[1] = 0x35;
+            put32(p + 2, got->sh_addr + 4);
+            p[6] = 0xff; /* jmp *(got + 8) */
+            p[7] = 0x25;
+            put32(p + 8, got->sh_addr + 8);
+            
+            /* relocation symbols in .dynsym and build PLT. */
+            plt_offset = 0;
+            sym_end = (Elf32_Sym *)(dynsym->data + dynsym->data_offset);
+            for(sym = (Elf32_Sym *)dynsym->data + 1; 
+                sym < sym_end;
+                sym++) {
+                type = ELF32_ST_TYPE(sym->st_info);
+                if (sym->st_shndx == SHN_UNDEF) {
+                    if (type == STT_FUNC) {
+                        /* one more entry in PLT */
+                        p = section_ptr_add(plt, 16);
+                        p[0] = 0xff; /* jmp *(got + x) */
+                        p[1] = 0x25;
+                        put32(p + 2, got->sh_addr + sym->st_value);
+                        p[6] = 0x68; /* push $xxx */
+                        put32(p + 7, plt_offset);
+                        p[11] = 0xe9; /* jmp plt_start */
+                        put32(p + 12, -(plt->data_offset));
+                        
+                        /* patch symbol value to point to plt */
+                        sym->st_value = plt->sh_addr + p - plt->data;
+                        
+                        plt_offset += 8;
+                    }
+                } else if (sym->st_shndx < SHN_LORESERVE) {
+                    /* do symbol relocation */
+                    sym->st_value += sections[sym->st_shndx]->sh_addr;
+                }
+            }
+            /* put dynamic section entries */
+
+            dynamic->data_offset = saved_dynamic_data_offset;
+            put_dt(dynamic, DT_HASH, dynsym->hash->sh_addr);
+            put_dt(dynamic, DT_STRTAB, dynstr->sh_addr);
+            put_dt(dynamic, DT_SYMTAB, dynsym->sh_addr);
+            put_dt(dynamic, DT_STRSZ, dynstr->data_offset);
+            put_dt(dynamic, DT_SYMENT, sizeof(Elf32_Sym));
+            put_dt(dynamic, DT_REL, rel_addr);
+            put_dt(dynamic, DT_RELSZ, rel_size);
+            put_dt(dynamic, DT_RELENT, sizeof(Elf32_Rel));
+            put_dt(dynamic, DT_NULL, 0);
+        }
+
+        ehdr.e_phentsize = sizeof(Elf32_Phdr);
+        ehdr.e_phnum = phnum;
+        ehdr.e_phoff = sizeof(Elf32_Ehdr);
+    }
+
+    /* all other sections come after */
+    for(i = 1; i < nb_sections; i++) {
+        s = sections[i];
+        if (phnum > 0 && (s->sh_flags & SHF_ALLOC))
+            continue;
+        section_order[sh_order_index++] = i;
+        
+        file_offset = (file_offset + s->sh_addralign - 1) & 
+            ~(s->sh_addralign - 1);
+        s->sh_offset = file_offset;
+        if (s->sh_type != SHT_NOBITS)
+            file_offset += s->sh_size;
+    }
+    
+    /* if building executable or DLL, then relocate each section
+       except the GOT which is already relocated */
+    if (file_type != TCC_OUTPUT_OBJ) {
+        relocate_syms(0);
+
+        /* relocate sections */
+        /* XXX: ignore sections with allocated relocations ? */
+        for(i = 1; i < nb_sections; i++) {
+            s = sections[i];
+            if (s->reloc && s != got)
+                relocate_section(s1, s);
+        }
+
+        /* relocate relocation entries if the relocation tables are
+           allocated in the executable */
+        for(i = 1; i < nb_sections; i++) {
+            s = sections[i];
+            if ((s->sh_flags & SHF_ALLOC) &&
+                s->sh_type == SHT_REL) {
+                relocate_rel(s);
+            }
+        }
+
+        /* get entry point address */
+        if (file_type == TCC_OUTPUT_EXE)
+            ehdr.e_entry = get_elf_sym_val("_start");
+        else
+            ehdr.e_entry = text_section->sh_addr; /* XXX: is it correct ? */
+    }
+
+    sort_syms(symtab_section);
+
+    /* align to 4 */
+    file_offset = (file_offset + 3) & -4;
+    
+    /* fill header */
+    ehdr.e_ident[0] = ELFMAG0;
+    ehdr.e_ident[1] = ELFMAG1;
+    ehdr.e_ident[2] = ELFMAG2;
+    ehdr.e_ident[3] = ELFMAG3;
+    ehdr.e_ident[4] = ELFCLASS32;
+    ehdr.e_ident[5] = ELFDATA2LSB;
+    ehdr.e_ident[6] = EV_CURRENT;
+    switch(file_type) {
+    default:
+    case TCC_OUTPUT_EXE:
+        ehdr.e_type = ET_EXEC;
+        break;
+    case TCC_OUTPUT_DLL:
+        ehdr.e_type = ET_DYN;
+        break;
+    case TCC_OUTPUT_OBJ:
+        ehdr.e_type = ET_REL;
+        break;
+    }
+    ehdr.e_machine = EM_386;
+    ehdr.e_version = EV_CURRENT;
+    ehdr.e_shoff = file_offset;
+    ehdr.e_ehsize = sizeof(Elf32_Ehdr);
+    ehdr.e_shentsize = sizeof(Elf32_Shdr);
+    ehdr.e_shnum = shnum;
+    ehdr.e_shstrndx = shnum - 1;
+    
+    /* write elf file */
+    if (file_type == TCC_OUTPUT_OBJ)
+        mode = 0666;
+    else
+        mode = 0777;
+    fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, mode); 
+    if (fd < 0)
+        error("could not write '%s'", filename);
+
+    f = fdopen(fd, "w");
+    fwrite(&ehdr, 1, sizeof(Elf32_Ehdr), f);
+    fwrite(phdr, 1, phnum * sizeof(Elf32_Phdr), f);
+    offset = sizeof(Elf32_Ehdr) + phnum * sizeof(Elf32_Phdr);
+    for(i=1;i<nb_sections;i++) {
+        s = sections[section_order[i]];
+        if (s->sh_type != SHT_NOBITS) {
+            while (offset < s->sh_offset) {
+                fputc(0, f);
+                offset++;
+            }
+            size = s->sh_size;
+            fwrite(s->data, 1, size, f);
+            offset += size;
+        }
+    }
+    while (offset < ehdr.e_shoff) {
+        fputc(0, f);
+        offset++;
+    }
+    
+    /* output section headers */
+    for(i=0;i<nb_sections;i++) {
+        sh = &shdr;
+        memset(sh, 0, sizeof(Elf32_Shdr));
+        s = sections[i];
+        if (s) {
+            sh->sh_name = s->sh_name;
+            sh->sh_type = s->sh_type;
+            sh->sh_flags = s->sh_flags;
+            sh->sh_entsize = s->sh_entsize;
+            sh->sh_info = s->sh_info;
+            if (s->link)
+                sh->sh_link = s->link->sh_num;
+            sh->sh_addralign = s->sh_addralign;
+            sh->sh_addr = s->sh_addr;
+            sh->sh_offset = s->sh_offset;
+            sh->sh_size = s->sh_size;
+        }
+        fwrite(sh, 1, sizeof(Elf32_Shdr), f);
+    }
+    fclose(f);
+
+    tcc_free(section_order);
+    tcc_free(phdr);
+    return 0;
+}
+
+static void *load_data(int fd, unsigned long file_offset, unsigned long size)
+{
+    void *data;
+
+    data = tcc_malloc(size);
+    lseek(fd, file_offset, SEEK_SET);
+    read(fd, data, size);
+    return data;
+}
+
+typedef struct SectionMergeInfo {
+    Section *s;            /* corresponding existing section */
+    unsigned long offset;  /* offset of the new section in the existing section */
+    int new_section;       /* true if section 's' was added */
+} SectionMergeInfo;
+
+/* load an object file and merge it with current files */
+/* XXX: handle correctly stab (debug) info */
+static int tcc_load_object_file(TCCState *s1, 
+                                int fd, unsigned long file_offset)
+{ 
+    Elf32_Ehdr ehdr;
+    Elf32_Shdr *shdr, *sh;
+    int size, i, j, offset, offseti, nb_syms, sym_index;
+    unsigned char *strsec, *strtab;
+    int *old_to_new_syms;
+    char *sh_name, *name;
+    SectionMergeInfo *sm_table, *sm;
+    Elf32_Sym *sym, *symtab;
+    Elf32_Rel *rel, *rel_end;
+    Section *s;
+
+    if (read(fd, &ehdr, sizeof(ehdr)) != sizeof(ehdr))
+        goto fail;
+    if (ehdr.e_ident[0] != ELFMAG0 ||
+        ehdr.e_ident[1] != ELFMAG1 ||
+        ehdr.e_ident[2] != ELFMAG2 ||
+        ehdr.e_ident[3] != ELFMAG3)
+        goto fail;
+    /* test if object file */
+    if (ehdr.e_type != ET_REL)
+        goto fail;
+    /* test CPU specific stuff */
+    if (ehdr.e_ident[5] != ELFDATA2LSB ||
+        ehdr.e_machine != EM_386) {
+    fail:
+        error("invalid object file");
+    }
+    /* read sections */
+    shdr = load_data(fd, file_offset + ehdr.e_shoff, 
+                     sizeof(Elf32_Shdr) * ehdr.e_shnum);
+    sm_table = tcc_mallocz(sizeof(SectionMergeInfo) * ehdr.e_shnum);
+    
+    /* load section names */
+    sh = &shdr[ehdr.e_shstrndx];
+    strsec = load_data(fd, file_offset + sh->sh_offset, sh->sh_size);
+
+    /* load symtab and strtab */
+    symtab = NULL;
+    strtab = NULL;
+    nb_syms = 0;
+    for(i = 1; i < ehdr.e_shnum; i++) {
+        sh = &shdr[i];
+        if (sh->sh_type == SHT_SYMTAB) {
+            if (symtab)
+                error("object must contain only one symtab");
+            nb_syms = sh->sh_size / sizeof(Elf32_Sym);
+            symtab = load_data(fd, file_offset + sh->sh_offset, sh->sh_size);
+            sm_table[i].s = symtab_section;
+
+            /* now load strtab */
+            sh = &shdr[sh->sh_link];
+            strtab = load_data(fd, file_offset + sh->sh_offset, sh->sh_size);
+        }
+    }
+        
+    /* now examine each section and try to merge its content with the
+       ones in memory */
+    for(i = 1; i < ehdr.e_shnum; i++) {
+        /* no need to examine section name strtab */
+        if (i == ehdr.e_shstrndx)
+            continue;
+        sh = &shdr[i];
+        sh_name = strsec + sh->sh_name;
+        /* ignore sections types we do not handle */
+        if (sh->sh_type != SHT_PROGBITS &&
+            sh->sh_type != SHT_REL && 
+            sh->sh_type != SHT_NOBITS)
+            continue;
+        if (sh->sh_addralign < 1)
+            sh->sh_addralign = 1;
+        /* find corresponding section, if any */
+        for(j = 1; j < nb_sections;j++) {
+            s = sections[j];
+            if (!strcmp(s->name, sh_name))
+                goto found;
+        }
+        /* not found: create new section */
+        s = new_section(sh_name, sh->sh_type, sh->sh_flags);
+        /* take as much info as possible from the section. sh_link and
+           sh_info will be updated later */
+        s->sh_addralign = sh->sh_addralign;
+        s->sh_entsize = sh->sh_entsize;
+        sm_table[i].new_section = 1;
+    found:
+        if (sh->sh_type != s->sh_type)
+            goto fail;
+
+        /* align start of section */
+        offset = s->data_offset;
+        size = sh->sh_addralign - 1;
+        offset = (offset + size) & ~size;
+        if (sh->sh_addralign > s->sh_addralign)
+            s->sh_addralign = sh->sh_addralign;
+        s->data_offset = offset;
+        sm_table[i].offset = offset;
+        sm_table[i].s = s;
+        /* concatenate sections */
+        size = sh->sh_size;
+        if (sh->sh_type != SHT_NOBITS) {
+            unsigned char *ptr;
+            lseek(fd, file_offset + sh->sh_offset, SEEK_SET);
+            ptr = section_ptr(s, size);
+            read(fd, ptr, size);
+        }
+        s->data_offset += size;
+    }
+
+    /* second short pass to update sh_link and sh_info fields of new
+       sections */
+    sm = sm_table;
+    for(i = 1; i < ehdr.e_shnum; i++) {
+        s = sm_table[i].s;
+        if (!s || !sm_table[i].new_section)
+            continue;
+        sh = &shdr[i];
+        if (sh->sh_link > 0)
+            s->link = sm_table[sh->sh_link].s;
+        if (sh->sh_type == SHT_REL) {
+            s->sh_info = sm_table[sh->sh_info].s->sh_num;
+            /* update backward link */
+            sections[s->sh_info]->reloc = s;
+        }
+    }
+
+    /* resolve symbols */
+    old_to_new_syms = tcc_mallocz(nb_syms * sizeof(int));
+
+    sym = symtab + 1;
+    for(i = 1; i < nb_syms; i++, sym++) {
+        if (sym->st_shndx != SHN_UNDEF &&
+            sym->st_shndx < SHN_LORESERVE) {
+            sm = &sm_table[sym->st_shndx];
+            /* if no corresponding section added, no need to add symbol */
+            if (!sm->s)
+                continue;
+            /* convert section number */
+            sym->st_shndx = sm->s->sh_num;
+            /* offset value */
+            sym->st_value += sm->offset;
+        }
+        /* add symbol */
+        name = strtab + sym->st_name;
+        sym_index = add_elf_sym(symtab_section, sym->st_value, sym->st_size, 
+                                sym->st_info, sym->st_shndx, name);
+        old_to_new_syms[i] = sym_index;
+    }
+
+    /* third pass to patch relocation entries */
+    for(i = 1; i < ehdr.e_shnum; i++) {
+        s = sm_table[i].s;
+        if (!s)
+            continue;
+        sh = &shdr[i];
+        offset = sm_table[i].offset;
+        switch(s->sh_type) {
+        case SHT_REL:
+            /* take relocation offset information */
+            offseti = sm_table[sh->sh_info].offset;
+            rel_end = (Elf32_Rel *)(s->data + s->data_offset);
+            for(rel = (Elf32_Rel *)(s->data + offset);
+                rel < rel_end;
+                rel++) {
+                int type;
+                unsigned sym_index;
+                /* convert symbol index */
+                type = ELF32_R_TYPE(rel->r_info);
+                sym_index = ELF32_R_SYM(rel->r_info);
+                /* NOTE: only one symtab assumed */
+                if (sym_index >= nb_syms)
+                    goto invalid_reloc;
+                sym_index = old_to_new_syms[sym_index];
+                if (!sym_index) {
+                invalid_reloc:
+                    error("Invalid relocation entry");
+                }
+                rel->r_info = ELF32_R_INFO(sym_index, type);
+                /* offset the relocation offset */
+                rel->r_offset += offseti;
+            }
+            break;
+        default:
+            break;
+        }
+    }
+    tcc_free(symtab);
+    tcc_free(strtab);
+    tcc_free(old_to_new_syms);
+    tcc_free(sm_table);
+    tcc_free(shdr);
+    return 0;
+}
+
+#define ARMAG  "!<arch>\012"	/* For COFF and a.out archives */
+
+typedef struct ArchiveHeader {
+    char ar_name[16];		/* name of this member */
+    char ar_date[12];		/* file mtime */
+    char ar_uid[6];		/* owner uid; printed as decimal */
+    char ar_gid[6];		/* owner gid; printed as decimal */
+    char ar_mode[8];		/* file mode, printed as octal   */
+    char ar_size[10];		/* file size, printed as decimal */
+    char ar_fmag[2];		/* should contain ARFMAG */
+} ArchiveHeader;
+
+/* load a '.a' file */
+static int tcc_load_archive(TCCState *s1, int fd)
+{
+    ArchiveHeader hdr;
+    char ar_size[11];
+    char ar_name[17];
+    char magic[8];
+    int size, len, i;
+    unsigned long file_offset;
+
+    /* skip magic which was already checked */
+    read(fd, magic, sizeof(magic));
+    
+    for(;;) {
+        len = read(fd, &hdr, sizeof(hdr));
+        if (len == 0)
+            break;
+        if (len != sizeof(hdr))
+            error("invalid archive");
+        memcpy(ar_size, hdr.ar_size, sizeof(hdr.ar_size));
+        ar_size[sizeof(hdr.ar_size)] = '\0';
+        size = strtol(ar_size, NULL, 0);
+        memcpy(ar_name, hdr.ar_name, sizeof(hdr.ar_name));
+        for(i = sizeof(hdr.ar_name) - 1; i >= 0; i--) {
+            if (ar_name[i] != ' ')
+                break;
+        }
+        ar_name[i + 1] = '\0';
+        //        printf("name='%s' size=%d %s\n", ar_name, size, ar_size);
+        file_offset = lseek(fd, 0, SEEK_CUR);
+        if (!strcmp(ar_name, "/") ||
+            !strcmp(ar_name, "//") ||
+            !strcmp(ar_name, "__.SYMDEF") ||
+            !strcmp(ar_name, "__.SYMDEF/") ||
+            !strcmp(ar_name, "ARFILENAMES/")) {
+            /* skip symbol table or archive names */
+        } else {
+            tcc_load_object_file(s1, fd, file_offset);
+        }
+        /* align to even */
+        size = (size + 1) & ~1;
+        lseek(fd, file_offset + size, SEEK_SET);
+    }
+    return 0;
+}
+
+/* load a DLL and all referenced DLLs. 'level = 0' means that the DLL
+   is referenced by the user (so it should be added as DT_NEEDED in
+   the generated ELF file) */
+static int tcc_load_dll(TCCState *s1, int fd, const char *filename, int level)
+{ 
+    Elf32_Ehdr ehdr;
+    Elf32_Shdr *shdr, *sh, *sh1;
+    int i, nb_syms, nb_dts, sym_bind;
+    Elf32_Sym *sym, *dynsym;
+    Elf32_Dyn *dt, *dynamic;
+    unsigned char *dynstr;
+    const char *name, *soname, *p;
+    DLLReference *dllref;
+    
+    read(fd, &ehdr, sizeof(ehdr));
+
+    /* test CPU specific stuff */
+    if (ehdr.e_ident[5] != ELFDATA2LSB ||
+        ehdr.e_machine != EM_386)
+        error("bad architecture");
+
+    /* read sections */
+    shdr = load_data(fd, ehdr.e_shoff, sizeof(Elf32_Shdr) * ehdr.e_shnum);
+
+    /* load dynamic section and dynamic symbols */
+    nb_syms = 0;
+    nb_dts = 0;
+    dynamic = NULL;
+    dynsym = NULL; /* avoid warning */
+    dynstr = NULL; /* avoid warning */
+    for(i = 0, sh = shdr; i < ehdr.e_shnum; i++, sh++) {
+        switch(sh->sh_type) {
+        case SHT_DYNAMIC:
+            nb_dts = sh->sh_size / sizeof(Elf32_Dyn);
+            dynamic = load_data(fd, sh->sh_offset, sh->sh_size);
+            break;
+        case SHT_DYNSYM:
+            nb_syms = sh->sh_size / sizeof(Elf32_Sym);
+            dynsym = load_data(fd, sh->sh_offset, sh->sh_size);
+            sh1 = &shdr[sh->sh_link];
+            dynstr = load_data(fd, sh1->sh_offset, sh1->sh_size);
+            break;
+        default:
+            break;
+        }
+    }
+    
+    /* compute the real library name */
+    soname = filename;
+    p = strrchr(soname, '/');
+    if (p)
+        soname = p + 1;
+        
+    for(i = 0, dt = dynamic; i < nb_dts; i++, dt++) {
+        if (dt->d_tag == DT_SONAME) {
+            soname = dynstr + dt->d_un.d_val;
+        }
+    }
+
+    /* if the dll is already loaded, do not load it */
+    for(i = 0; i < nb_loaded_dlls; i++) {
+        dllref = loaded_dlls[i];
+        if (!strcmp(soname, dllref->name)) {
+            /* but update level if needed */
+            if (level < dllref->level)
+                dllref->level = level;
+            goto the_end;
+        }
+    }
+    
+    //    printf("loading dll '%s'\n", soname);
+
+    /* add the dll and its level */
+    dllref = tcc_malloc(sizeof(DLLReference) + strlen(soname));
+    dllref->level = level;
+    strcpy(dllref->name, soname);
+    dynarray_add((void ***)&loaded_dlls, &nb_loaded_dlls, dllref);
+
+    /* add dynamic symbols in dynsym_section */
+    for(i = 1, sym = dynsym + 1; i < nb_syms; i++, sym++) {
+        sym_bind = ELF32_ST_BIND(sym->st_info);
+        if (sym_bind == STB_LOCAL)
+            continue;
+        name = dynstr + sym->st_name;
+        add_elf_sym(dynsymtab_section, sym->st_value, sym->st_size,
+                    sym->st_info, sym->st_shndx, name);
+    }
+
+    /* load all referenced DLLs */
+    for(i = 0, dt = dynamic; i < nb_dts; i++, dt++) {
+        switch(dt->d_tag) {
+        case DT_NEEDED:
+            name = dynstr + dt->d_un.d_val;
+            for(i = 0; i < nb_loaded_dlls; i++) {
+                dllref = loaded_dlls[i];
+                if (!strcmp(name, dllref->name))
+                    goto already_loaded;
+            }
+            if (tcc_add_dll(s1, name, AFF_REFERENCED_DLL) < 0)
+                error("referenced dll '%s' not found", name);
+        already_loaded:
+            break;
+        }
+    }
+ the_end:
+    tcc_free(shdr);
+    return 0;
+}
+
+/* return -2 if error and CH_EOF if eof */
+static void ld_skipspaces(void)
+{
+    while (ch == ' ' || ch == '\t' || ch == '\n')
+        cinp();
+}
+
+static int ld_get_cmd(char *cmd, int cmd_size)
+{
+    char *q;
+
+    ld_skipspaces();
+    if (ch == CH_EOF)
+        return -1;
+    q = cmd;
+    for(;;) {
+        if (!((ch >= 'a' && ch <= 'z') ||
+              (ch >= 'A' && ch <= 'Z') ||
+              (ch >= '0' && ch <= '9') ||
+              strchr("/.-_+=$:\\,~?*", ch)))
+            break;
+        if ((q - cmd) >= (cmd_size - 1))
+            return -2;
+        *q++ = ch;
+        cinp();
+    }
+    *q = '\0';
+    return 0;
+}
+                     
+/* interpret a subset of GNU ldscripts to handle the dummy libc.so
+   files */
+static int tcc_load_ldscript(TCCState *s1)
+{
+    char cmd[64];
+    char filename[1024];
+    int ret;
+    
+    inp();
+    cinp();
+    for(;;) {
+        ret = ld_get_cmd(cmd, sizeof(cmd));
+        if (ret == CH_EOF)
+            return 0;
+        else if (ret < 0)
+            return -1;
+        //        printf("cmd='%s'\n", cmd);
+        if (!strcmp(cmd, "INPUT") ||
+            !strcmp(cmd, "GROUP")) {
+            ld_skipspaces();
+            if (ch != '(')
+                expect("(");
+            cinp();
+            for(;;) {
+                ld_get_cmd(filename, sizeof(filename));
+                tcc_add_file(s1, filename);
+                ld_skipspaces();
+                if (ch == ',') {
+                    cinp();
+                } else if (ch == ')') {
+                    cinp();
+                    break;
+                } else if (ch == CH_EOF) {
+                    error("unexpected end of file");
+                }
+            }
+        } else {
+            return -1;
+        }
+    }
+    return 0;
+}
+