[Bug c++/94264] Array-to-pointer conversion not performed on array prvalues
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94264 Jason Merrill changed: What|Removed |Added Status|ASSIGNED|RESOLVED Target Milestone|--- |14.0 Resolution|--- |FIXED --- Comment #10 from Jason Merrill --- Fixed for GCC 14.
[Bug c++/94264] Array-to-pointer conversion not performed on array prvalues
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94264 --- Comment #9 from GCC Commits --- The master branch has been updated by Patrick Palka : https://gcc.gnu.org/g:5764825aed613f201a8bc47e5b239027a39691f0 commit r14-6342-g5764825aed613f201a8bc47e5b239027a39691f0 Author: Patrick Palka Date: Fri Dec 8 13:33:55 2023 -0500 c++: undiagnosed error_mark_node from cp_build_c_cast [PR112658] When cp_build_c_cast commits to an erroneous const_cast, we neglect to replay errors from build_const_cast_1 which can lead to us incorrectly accepting (and "miscompiling") the cast, or triggering the assert in finish_expr_stmt. This patch fixes this oversight. This was the original fix for the ICE in PR112658 before r14-5941-g305a2686c99bf9 made us accept the testcase there after all. I wasn't able to come up with an alternate testcase for which this fix has an effect anymore, but below is a reduced version of the PR112658 testcase (accepted ever since r14-5941) for good measure. PR c++/112658 PR c++/94264 gcc/cp/ChangeLog: * typeck.cc (cp_build_c_cast): If we're committed to a const_cast and the result is erroneous, call build_const_cast_1 a second time to issue errors. Use complain=tf_none instead of =false. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/initlist-array20.C: New test.
[Bug c++/94264] Array-to-pointer conversion not performed on array prvalues
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94264 --- Comment #8 from GCC Commits --- The trunk branch has been updated by Jason Merrill : https://gcc.gnu.org/g:305a2686c99bf9b57490419f25c79f6fb3ae0feb commit r14-5941-g305a2686c99bf9b57490419f25c79f6fb3ae0feb Author: Jason Merrill Date: Tue Nov 28 13:54:47 2023 -0500 c++: prvalue array decay [PR94264] My change for PR53220 made array to pointer decay for prvalue arrays ill-formed to catch well-defined C code that produces a dangling pointer in C++ due to the shorter lifetime of compound literals. This wasn't really correct, but wasn't a problem until C++17 added prvalue arrays, at which point it started rejecting valid C++ code. I wanted to make sure that we still diagnose the problematic code; -Wdangling-pointer covers the array-lit.c case, but I needed to extend -Wreturn-local-addr to handle the return case. PR c++/94264 PR c++/53220 gcc/c/ChangeLog: * c-typeck.cc (array_to_pointer_conversion): Adjust -Wc++-compat diagnostic. gcc/cp/ChangeLog: * call.cc (convert_like_internal): Remove obsolete comment. * typeck.cc (decay_conversion): Allow array prvalue. (maybe_warn_about_returning_address_of_local): Check for returning pointer to temporary. gcc/testsuite/ChangeLog: * c-c++-common/array-lit.c: Adjust. * g++.dg/cpp1z/array-prvalue1.C: New test. * g++.dg/ext/complit17.C: New test.
[Bug c++/94264] Array-to-pointer conversion not performed on array prvalues
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94264 Jason Merrill changed: What|Removed |Added CC||jason at gcc dot gnu.org Assignee|unassigned at gcc dot gnu.org |jason at gcc dot gnu.org Depends on||53220 Status|NEW |ASSIGNED --- Comment #7 from Jason Merrill --- This is due to my PR53220 change to discourage use of compound-literals in ways that produce a dangling pointer when the C++ compiler treats them as prvalues, unlike C where they have variable lifetime. I think the change was always wrong, but wasn't really a problem until we added array prvalues in C++17. Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53220 [Bug 53220] [4.7/4.8 Regression] g++ mis-compiles compound literals
[Bug c++/94264] Array-to-pointer conversion not performed on array prvalues
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94264
--- Comment #6 from Andrew Pinski ---
(In reply to Nick Krempel from comment #0)
> T{1, 2} + 1;
> Ditto.
That is what clang's issue: https://github.com/llvm/llvm-project/issues/54016
is about even.
[Bug c++/94264] Array-to-pointer conversion not performed on array prvalues
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94264 Jiang An changed: What|Removed |Added CC||de34 at live dot cn --- Comment #5 from Jiang An --- Related: https://cplusplus.github.io/CWG/issues/2548.html
[Bug c++/94264] Array-to-pointer conversion not performed on array prvalues
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94264
Fedor Chelnokov changed:
What|Removed |Added
CC||fchelnokov at gmail dot com
--- Comment #4 from Fedor Chelnokov ---
Related discussion: https://stackoverflow.com/q/77051011/7325599
And an example from it:
int main() {
using U = int(&&)[1];
(void) *U{}; //ok everywhere
using T = int[1];
(void) *T{}; //error in GCC
}
Online demo: https://godbolt.org/z/4s8v9PPqT
[Bug c++/94264] Array-to-pointer conversion not performed on array prvalues
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94264 Andrew Pinski changed: What|Removed |Added CC||kamkaz at windowslive dot com --- Comment #3 from Andrew Pinski --- *** Bug 102568 has been marked as a duplicate of this bug. ***
[Bug c++/94264] Array-to-pointer conversion not performed on array prvalues
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94264 Andrew Pinski changed: What|Removed |Added CC||dchneric at gmail dot com --- Comment #2 from Andrew Pinski --- *** Bug 89931 has been marked as a duplicate of this bug. ***
[Bug c++/94264] Array-to-pointer conversion not performed on array prvalues
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94264
Marek Polacek changed:
What|Removed |Added
Last reconfirmed||2020-04-18
CC||mpolacek at gcc dot gnu.org
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
--- Comment #1 from Marek Polacek ---
cp_build_binary_op calls cp_default_conversion on its operands and that calls
decay_conversion which has:
2153 /* Don't let an array compound literal decay to a pointer. It can
2154 still be used to initialize an array or bind to a reference. */
2155 if (TREE_CODE (exp) == TARGET_EXPR)
2156 {
2157 if (complain & tf_error)
2158 error_at (loc, "taking address of temporary array");
2159 return error_mark_node;
2160 }
convert_like_real does
+ /* Take the address explicitly rather than via decay_conversion
+ to avoid the error about taking the address of a temporary. */
+ array = cp_build_addr_expr (array, complain);
+ array = cp_convert (build_pointer_type (elttype), array);
to avoid that error.
