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Evaluate arguments of sizeof that are structs of variable size.

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Evaluate arguments of sizeof for all types of variable size
and not just for VLAs. This fixes some issues related to
[PR29970] where statement expressions need to be evaluated
so that the size is well defined.

2021-08-10  Martin Uecker  <muecker@gwdg.de>

gcc/c/
	PR c/29970
	* c-typeck.c (c_expr_sizeof_expr): Evaluate
	size expressions for structs of variable size.

gcc/testsuite/
	PR c/29970
	* gcc.dg/vla-stexp-1.c: New test.
This commit is contained in:
Martin Uecker 2021-08-10 07:42:51 +02:00
parent 3d7ccbc1ef
commit 0631faf87a
2 changed files with 19 additions and 1 deletions
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2
gcc/c/c-typeck.c
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@ -2992,7 +2992,7 @@ c_expr_sizeof_expr (location_t loc, struct c_expr expr)
c_last_sizeof_loc = loc;
ret.original_code = SIZEOF_EXPR;
ret.original_type = NULL;
if (c_vla_type_p (TREE_TYPE (folded_expr)))
if (C_TYPE_VARIABLE_SIZE (TREE_TYPE (folded_expr)))
{
/* sizeof is evaluated when given a vla (C99 6.5.3.4p2). */
ret.value = build2 (C_MAYBE_CONST_EXPR, TREE_TYPE (ret.value),

18
gcc/testsuite/gcc.dg/vla-stexp-1.c Normal file
View File

@ -0,0 +1,18 @@
/* PR29970*/
/* { dg-do run } */
/* { dg-options "-Wall -O0" } */
int foo(void)
{
int n = 0;
return sizeof(*({ n = 10; struct foo { int x[n]; } x; &x; }));
}
int main()
{
if (sizeof(struct foo { int x[10]; }) != foo())
__builtin_abort();
return 0;
}