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c++: Fix up handling of references to anon union members in initializers [PR53932]

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For anonymous union members we create artificial VAR_DECLs which
have DECL_VALUE_EXPR for the actual COMPONENT_REF.  That works
just fine inside of functions (including global dynamic constructors),
because during gimplification such VAR_DECLs are gimplified as
their DECL_VALUE_EXPR.  This is also done during regimplification.

But references to these artificial vars in DECL_INITIAL expressions
aren't ever replaced by the DECL_VALUE_EXPRs, so we end up either
with link failures like on the testcase below, or worse ICEs with
LTO.

The following patch fixes those during cp_fully_fold_init where we
already walk all the trees (!data->genericize means that
function rather than cp_fold_function).

2023-01-19  Jakub Jelinek  <jakub@redhat.com>

	PR c++/53932
	* cp-gimplify.cc (cp_fold_r): During cp_fully_fold_init replace
	DECL_ANON_UNION_VAR_P VAR_DECLs with their corresponding
	DECL_VALUE_EXPR.

	* g++.dg/init/pr53932.C: New test.
This commit is contained in:
Jakub Jelinek
2023-01-19 23:27:34 +01:00
parent c81e68a9cd
commit 9b9a989adc
2 changed files with 35 additions and 0 deletions
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10
gcc/cp/cp-gimplify.cc
View File

@@ -1010,6 +1010,16 @@ cp_fold_r (tree *stmt_p, int *walk_subtrees, void *data_)
}
break;
case VAR_DECL:
/* In initializers replace anon union artificial VAR_DECLs
with their DECL_VALUE_EXPRs, as nothing will do it later. */
if (DECL_ANON_UNION_VAR_P (stmt) && !data->genericize)
{
*stmt_p = stmt = unshare_expr (DECL_VALUE_EXPR (stmt));
break;
}
break;
default:
break;
}

25
gcc/testsuite/g++.dg/init/pr53932.C Normal file
View File

@@ -0,0 +1,25 @@
// PR c++/53932
// { dg-do link }
static union { int i; };
int &r = i;
int s = i;
int *t = &i;
void
foo (int **p, int *q)
{
static int &u = i;
static int v = i;
static int *w = &i;
int &x = i;
int y = i;
int *z = &i;
*p = &i;
*q = i;
}
int
main ()
{
}