Fix more bitfield corner cases

Our code generation assumes that it can load/store with the
bit-fields base type, so bit_pos/bit_size must be in range for this.
We could change the fields type or adjust offset/bit_pos; we do the
latter.

2 files changed, 9 insertions, 0 deletions

diff --git a/tccgen.c b/tccgen.c
index a5de7e9..1efbc1f 100644
--- a/tccgen.c
+++ b/tccgen.c
@@ -3391,6 +3391,9 @@ static void struct_layout(CType *type, AttributeDef *ad)
 		     (ofs2 / (typealign * 8)) > (size/typealign))) {
 		    c = (c + ((bit_pos + 7) >> 3) + typealign - 1) & -typealign;
 		    bit_pos = 0;
+		} else while (bit_pos + bit_size > size * 8) {
+		    c += size;
+		    bit_pos -= size * 8;
 		}
 		offset = c;
 		/* In PCC layout named bit-fields influence the alignment
diff --git a/tests/tcctest.c b/tests/tcctest.c
index dc6a060..aee0120 100644
--- a/tests/tcctest.c
+++ b/tests/tcctest.c
@@ -2082,6 +2082,12 @@ void bitfield_test(void)
 	char c;
     } st5 = { 1, 2, 3, 4, -3, 6 };
     printf("st5 = %d %d %d %d %d %d\n", st5.a, st5.b, st5.x, st5.y, st5.z, st5.c);
+    struct sbf6 {
+	short x : 12;
+	unsigned char y : 2;
+    } st6;
+    st6.y = 1;
+    printf("st6.y == %d\n", st6.y);
 }
 
 #ifdef __x86_64__