d0p1/tcc-stupidos
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bitfields: Fix MS layout some more

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Another corner case:
  struct foo6_1
  {
    char x;
    short p:8;
    short :0;
    short :0;
    short p2:8;
    char y;
  };

In MS layout the second anon :0 bit-field does _not_ adjust size or
alignment of the struct again.  The first one does, though.
This commit is contained in:
Michael Matz 2016-11-28 20:27:42 +01:00
parent ed680da951
commit 23b257a8d2
1 changed files with 9 additions and 4 deletions
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13
tccgen.c
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@ -3266,7 +3266,7 @@ static void struct_add_offset (Sym *s, int offset)
static void struct_layout(CType *type, AttributeDef *ad)
{
int align, maxalign, offset, c, bit_pos, bt, prevbt;
int align, maxalign, offset, c, bit_pos, bt, prevbt, prev_bit_size;
int pcc = !tcc_state->ms_bitfields;
Sym *f;
if (ad->a.aligned)
@ -3277,6 +3277,7 @@ static void struct_layout(CType *type, AttributeDef *ad)
c = 0;
bit_pos = 0;
prevbt = VT_STRUCT; /* make it never match */
prev_bit_size = 0;
for (f = type->ref->next; f; f = f->next) {
int extra_bytes = 0;
int typealign, bit_size;
@ -3314,6 +3315,7 @@ static void struct_layout(CType *type, AttributeDef *ad)
if (extra_bytes) c += extra_bytes;
else if (bit_size < 0) {
prevbt = VT_STRUCT;
prev_bit_size = 0;
if (type->ref->type.t == TOK_STRUCT) {
int addbytes = pcc ? (bit_pos + 7) >> 3 : 0;
c = (c + addbytes + align - 1) & -align;
@ -3355,14 +3357,15 @@ static void struct_layout(CType *type, AttributeDef *ad)
(bit_pos + bit_size > size * 8)
) {*/
if (bit_size == 0 ||
(typealign != 1 && (ofs2 / (typealign * 8)) > ((size*8)/(typealign*8)))) {
(typealign != 1 && (ofs2 / (typealign * 8)) > (size/typealign))) {
c = (c + ((bit_pos + 7) >> 3) + typealign - 1) & -typealign;
bit_pos = 0;
}
offset = c;
/* In PCC layout named bit-fields influence the alignment
of the containing struct using the base types alignment,
except for packed fields or zero-width fields. */
except for packed fields (which here have correct
align/typealign). */
if (!(f->v & SYM_FIRST_ANOM)) {
if (align > maxalign)
maxalign = align;
@ -3381,7 +3384,8 @@ static void struct_layout(CType *type, AttributeDef *ad)
bit_pos = 0;
/* In MS bitfield mode a bit-field run always uses
at least as many bits as the underlying type. */
c += size;
if (bit_size || prev_bit_size)
c += size;
}
if (bit_size > 0 || prevbt == bt) {
if (align > maxalign)
@ -3390,6 +3394,7 @@ static void struct_layout(CType *type, AttributeDef *ad)
maxalign = typealign;
}
prevbt = bt;
prev_bit_size = bit_size;
}
f->type.t = (f->type.t & ~(0x3f << VT_STRUCT_SHIFT))
| (bit_pos << VT_STRUCT_SHIFT);