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re PR c++/89481 (constexpr function allows writing one active union member and reading another)

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PR c++/89481
	* constexpr.c (cxx_eval_store_expression): When changing active union
	member, set no_zero_init.

	* g++.dg/cpp1y/constexpr-89481.C: New test.

From-SVN: r269213
This commit is contained in:
Jakub Jelinek 2019-02-26 15:37:39 +01:00 committed by Jakub Jelinek
parent 01c3ddcffb
commit c7f7c313c0
4 changed files with 36 additions and 0 deletions
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6
gcc/cp/ChangeLog
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@ -1,3 +1,9 @@
2019-02-26 Jakub Jelinek <jakub@redhat.com>
PR c++/89481
* constexpr.c (cxx_eval_store_expression): When changing active union
member, set no_zero_init.
2019-02-23 Marek Polacek <polacek@redhat.com>
PR c++/88294 - ICE with non-constant noexcept-specifier.

1
gcc/cp/constexpr.c
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@ -3860,6 +3860,7 @@ cxx_eval_store_expression (const constexpr_ctx *ctx, tree t,
}
/* Changing active member. */
vec_safe_truncate (CONSTRUCTOR_ELTS (*valp), 0);
no_zero_init = true;
}
for (idx = 0;

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2019-02-26 Jakub Jelinek <jakub@redhat.com>
PR c++/89481
* g++.dg/cpp1y/constexpr-89481.C: New test.
2019-02-26 Richard Biener <rguenther@suse.de>
PR tree-optimization/89505

24
gcc/testsuite/g++.dg/cpp1y/constexpr-89481.C Normal file
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@ -0,0 +1,24 @@
// PR c++/89481
// { dg-do compile { target c++14 } }
constexpr int
foo ()
{
union U { long long a; int b[2]; } u { 5LL };
u.b[1] = 4; // { dg-error "change of the active member of a union from" "" { target c++17_down } }
return u.b[0];
}
constexpr int
bar ()
{
union U { long long a; int b[2]; } u { 5LL };
u.b[1] = 4; // { dg-error "change of the active member of a union from" "" { target c++17_down } }
return u.b[1];
}
static_assert (foo () == 0, ""); // { dg-error "non-constant condition for static assertion" }
// { dg-message "in 'constexpr' expansion of" "" { target *-*-* } .-1 }
// { dg-error "accessing uninitialized array element" "" { target c++2a } .-2 }
static_assert (bar () == 4, ""); // { dg-error "non-constant condition for static assertion" "" { target c++17_down } }
// { dg-message "in 'constexpr' expansion of" "" { target c++17_down } .-1 }