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C: Fix type compatibility for structs with variable sized fields.

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This fixes the test gcc.dg/gnu23-tag-4.c introduced by commit 23fee88f
which fails for -march=... because the DECL_FIELD_BIT_OFFSET are set
inconsistently for types with and without variable-sized field.  This
is fixed by testing for DECL_ALIGN instead.  The code is further
simplified by removing some unnecessary conditions, i.e. anon_field is
set unconditionaly and all fields are assumed to be DECL_FIELDs.

gcc/c:
	* c-typeck.cc (tagged_types_tu_compatible_p): Revise.

gcc/testsuite:
	* gcc.dg/c23-tag-9.c: New test.
This commit is contained in:
Martin Uecker
2023-12-22 17:32:34 +01:00
parent 77f30e22f1
commit 38c33fd2b5
2 changed files with 16 additions and 11 deletions
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19
gcc/c/c-typeck.cc
View File

@@ -1511,8 +1511,6 @@ tagged_types_tu_compatible_p (const_tree t1, const_tree t2,
if (!data->anon_field && TYPE_STUB_DECL (t1) != TYPE_STUB_DECL (t2))
data->different_types_p = true;
data->anon_field = false;
/* Incomplete types are incompatible inside a TU. */
if (TYPE_SIZE (t1) == NULL || TYPE_SIZE (t2) == NULL)
return false;
@@ -1592,22 +1590,21 @@ tagged_types_tu_compatible_p (const_tree t1, const_tree t2,
s1 && s2;
s1 = DECL_CHAIN (s1), s2 = DECL_CHAIN (s2))
{
if (TREE_CODE (s1) != TREE_CODE (s2)
|| DECL_NAME (s1) != DECL_NAME (s2))
gcc_assert (TREE_CODE (s1) == FIELD_DECL);
gcc_assert (TREE_CODE (s2) == FIELD_DECL);
if (DECL_NAME (s1) != DECL_NAME (s2))
return false;
if (!DECL_NAME (s1) && RECORD_OR_UNION_TYPE_P (TREE_TYPE (s1)))
data->anon_field = true;
if (DECL_ALIGN (s1) != DECL_ALIGN (s2))
return false;
data->anon_field = !DECL_NAME (s1);
data->cache = &entry;
if (!comptypes_internal (TREE_TYPE (s1), TREE_TYPE (s2), data))
return false;
if (TREE_CODE (s1) == FIELD_DECL
&& simple_cst_equal (DECL_FIELD_BIT_OFFSET (s1),
DECL_FIELD_BIT_OFFSET (s2)) != 1)
return false;
tree st1 = TYPE_SIZE (TREE_TYPE (s1));
tree st2 = TYPE_SIZE (TREE_TYPE (s2));

8
gcc/testsuite/gcc.dg/c23-tag-9.c Normal file
View File

@@ -0,0 +1,8 @@
/* { dg-do compile } */
/* { dg-options "-std=c23" } */
struct foo { int x; } x;
struct foo { alignas(128) int x; } y; /* { dg-error "redefinition" } */
static_assert(alignof(y) == 128);