| Summary: | use of pseudo-destructor accepted in constant expression | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Martin Sebor <msebor> |
| Component: | c++ | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | CC: | daniel.kruegler, gabravier, qurong, webrown.cpp |
| Priority: | P3 | Keywords: | accepts-invalid |
| Version: | 7.0 | ||
| Target Milestone: | 14.0 | ||
| See Also: |
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102623 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113031 |
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| Host: | Target: | ||
| Build: | Known to work: | ||
| Known to fail: | 5.3.0, 6.1.0, 7.0 | Last reconfirmed: | 2021-08-11 00:00:00 |
| Bug Depends on: | |||
| Bug Blocks: | 55004 | ||
Confirmed. Setting Status to Confirmed per comment #1. Note p->~T() is valid for C++20 but not exactly. The trunk branch has been updated by Jason Merrill <jason@gcc.gnu.org>: https://gcc.gnu.org/g:90bc2d09b5bfcc913f79543c3b65202e7246e162 commit r14-6508-g90bc2d09b5bfcc913f79543c3b65202e7246e162 Author: Nathaniel Shead <nathanieloshead@gmail.com> Date: Fri Nov 3 12:18:29 2023 +1100 c++: End lifetime of objects in constexpr after destructor call [PR71093] This patch adds checks for using objects after they've been manually destroyed via explicit destructor call. Currently this is only implemented for 'top-level' objects; FIELD_DECLs and individual elements of arrays will need a lot more work to track correctly and are left for a future patch. The other limitation is that destruction of parameter objects is checked too 'early', happening at the end of the function call rather than the end of the owning full-expression as they should be for consistency; see cpp2a/constexpr-lifetime2.C. This is because I wasn't able to find a good way to link the constructed parameter declarations with the variable declarations that are actually destroyed later on to propagate their lifetime status, so I'm leaving this for a later patch. PR c++/71093 gcc/cp/ChangeLog: * constexpr.cc (constexpr_global_ctx::get_value_ptr): Don't return NULL_TREE for objects we're initializing. (constexpr_global_ctx::destroy_value): Rename from remove_value. Only mark real variables as outside lifetime. (constexpr_global_ctx::clear_value): New function. (destroy_value_checked): New function. (cxx_eval_call_expression): Defer complaining about non-constant arg0 for operator delete. Use remove_value_safe. (cxx_fold_indirect_ref_1): Handle conversion to 'as base' type. (outside_lifetime_error): Include name of object we're accessing. (cxx_eval_store_expression): Handle clobbers. Improve error messages. (cxx_eval_constant_expression): Use remove_value_safe. Clear bind variables before entering body. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/constexpr-lifetime1.C: Improve error message. * g++.dg/cpp1y/constexpr-lifetime2.C: Likewise. * g++.dg/cpp1y/constexpr-lifetime3.C: Likewise. * g++.dg/cpp1y/constexpr-lifetime4.C: Likewise. * g++.dg/cpp2a/bitfield2.C: Likewise. * g++.dg/cpp2a/constexpr-new3.C: Likewise. New check. * g++.dg/cpp1y/constexpr-lifetime7.C: New test. * g++.dg/cpp2a/constexpr-lifetime1.C: New test. * g++.dg/cpp2a/constexpr-lifetime2.C: New test. Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com> This causes new ICEs for the libstdc++ test suite, see PR 113031 *** Bug 102623 has been marked as a duplicate of this bug. *** Fixed. *** Bug 119082 has been marked as a duplicate of this bug. *** |
Among the list of expressions that are not core constant expressions and thus are not usable in constexpr contexts is the call to a pseudo-destructor such as in the following (invalid) test case. The test case is silently accepted by all versions of GCC when it should be rejected. $ cat xx.cpp && gcc -S -Wall -Wextra -Wpedantic -o/dev/null xx.cpp constexpr int f (const int *p) { typedef int T; p->~T (); return *p; } constexpr int i = 0; constexpr int j = f (&i);