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c++: Fix cp_genericize_target_expr for TARGET_EXPRs created for global initialization [PR104031]

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The following patch is miscompiled, cp_genericize_target_expr expects
that for the constant part split_nonconstant_init will emit an INIT_EXPR
that will initialize it, but that doesn't happen and instead we get
DECL_INITIAL on the TARGET_EXPR_SLOT that isn't initialized anywhere
in the IL.

The problem is that the TARGET_EXPR has been created while
current_function_decl was NULL, it is inside a global var initializer.
That means the build_local_temp created VAR_DECL has NULL DECL_CONTEXT.
Later on when genericizing the ssdf (current_function_decl is already
non-NULL), the new cp_genericize_target_expr is called and during
split_nonconstant_init it checks is_local_temp, but that due to the NULL
DECL_CONTEXT returns false.  DECL_CONTEXT is set only later on during
gimplification.

The following patch fixes it by setting DECL_CONTEXT also inside of
cp_genericize_target_expr, which fixes the testcase.  But if there are
better spots to do that, please let me know...

2022-01-17  Jakub Jelinek  <jakub@redhat.com>

	PR c++/104031
	* cp-gimplify.c (cp_genericize_target_expr): Set DECL_CONTEXT of
	TARGET_EXPR_SLOT to current_function_decl if it was NULL.

	* g++.dg/cpp1y/pr104031.C: New test.
This commit is contained in:
Jakub Jelinek 2022-01-17 18:10:34 +01:00
parent d3a5799335
commit aeca44768d
2 changed files with 30 additions and 2 deletions
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9
gcc/cp/cp-gimplify.c
View File

@ -930,9 +930,14 @@ cp_genericize_init_expr (tree *stmt_p)
static void
cp_genericize_target_expr (tree *stmt_p)
{
tree slot = TARGET_EXPR_SLOT (*stmt_p);
/* If TARGET_EXPR is created for some global var initializer, the slot
will have NULL and so is_local_temp will return false for it. If
this is a ssdf, set DECL_CONTEXT now. */
if (DECL_CONTEXT (slot) == NULL_TREE)
DECL_CONTEXT (slot) = current_function_decl;
cp_genericize_init (&TARGET_EXPR_INITIAL (*stmt_p),
TARGET_EXPR_INITIAL (*stmt_p),
TARGET_EXPR_SLOT (*stmt_p));
TARGET_EXPR_INITIAL (*stmt_p), slot);
}
/* Genericization context. */

23
gcc/testsuite/g++.dg/cpp1y/pr104031.C Normal file
View File

@ -0,0 +1,23 @@
// PR c++/104031
// { dg-do run { target c++14 } }
// { dg-options "-O2" }
struct A {
A () {}
~A () {}
};
struct B {
A a;
int b = 0;
};
struct C
{
[[gnu::noipa]]
C (B x) { if (x.b != 42) __builtin_abort (); }
};
static C c ({ .a = A{}, .b = 42 });
int
main ()
{
}