[pushed] c++: constexpr aggregate destruction [PR109357]
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Commit Message
Tested x86_64-pc-linux-gnu, applying to trunk.
-- 8< --
We were assuming that the result of evaluation of TARGET_EXPR_INITIAL would
always be the new value of the temporary, but that's not necessarily true
when the initializer is complex (i.e. target_expr_needs_replace). In that
case evaluating the initializer initializes the temporary as a side-effect.
PR c++/109357
gcc/cp/ChangeLog:
* constexpr.cc (cxx_eval_constant_expression) [TARGET_EXPR]:
Check for complex initializer.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/constexpr-dtor15.C: New test.
---
gcc/cp/constexpr.cc | 15 +++++++++++----
gcc/testsuite/g++.dg/cpp2a/constexpr-dtor15.C | 19 +++++++++++++++++++
2 files changed, 30 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/constexpr-dtor15.C
base-commit: 9964df74a9e99e850bf9b0b6ff5c47133f846db8
@@ -7230,16 +7230,23 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t,
non_constant_p, overflow_p);
if (*non_constant_p)
break;
- /* Adjust the type of the result to the type of the temporary. */
- r = adjust_temp_type (type, r);
+ /* If the initializer is complex, evaluate it to initialize slot. */
+ bool is_complex = target_expr_needs_replace (t);
+ if (!is_complex)
+ {
+ r = unshare_constructor (r);
+ /* Adjust the type of the result to the type of the temporary. */
+ r = adjust_temp_type (type, r);
+ ctx->global->put_value (slot, r);
+ }
if (TARGET_EXPR_CLEANUP (t) && !CLEANUP_EH_ONLY (t))
ctx->global->cleanups->safe_push (TARGET_EXPR_CLEANUP (t));
- r = unshare_constructor (r);
- ctx->global->put_value (slot, r);
if (ctx->save_exprs)
ctx->save_exprs->safe_push (slot);
if (lval)
return slot;
+ if (is_complex)
+ r = ctx->global->get_value (slot);
}
break;
new file mode 100644
@@ -0,0 +1,19 @@
+// PR c++/109357
+// { dg-do compile { target c++20 } }
+// { dg-prune-output "used but never defined" }
+
+struct basic_string {
+ char _M_local_buf;
+ basic_string();
+ constexpr basic_string(const char *) {}
+ constexpr ~basic_string();
+ constexpr basic_string& operator=(basic_string);
+};
+struct S1 {
+ basic_string x;
+ basic_string y;
+} s1;
+struct s2 {
+ ~s2();
+};
+s2::~s2() { s1 = {"", ""}; }