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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/107087] [12/13 Regression] bits/stl_algobase.h:431: warning: 'void* __builtin_memcpy(void*, const void*, unsigned int)' reading between 8 and 2147483644 bytes from a region of size 4 [-Wstringop-overread] Date: Fri, 31 Mar 2023 22:45:31 +0000 [thread overview] Message-ID: <bug-107087-4-R6ZKFx9vH6@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-107087-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107087 --- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>: https://gcc.gnu.org/g:4969dcd2b7a94ce6c0d07225b21b5f3c040a4902 commit r13-6962-g4969dcd2b7a94ce6c0d07225b21b5f3c040a4902 Author: Jonathan Wakely <jwakely@redhat.com> Date: Fri Mar 31 13:44:04 2023 +0100 libstdc++: Teach optimizer that empty COW strings are empty [PR107087] The compiler doesn't know about the invariant that the _S_empty_rep() object is immutable and so _M_length and _M_refcount are always zero. This means that we get warnings about writing possibly-non-zero length strings into buffers that can't hold them. If we teach the compiler that the empty rep is always zero length, it knows it can be copied into any buffer. For Stage 1 we might want to also consider adding this to capacity(): if (_S_empty_rep()._M_capacity != 0) __builtin_unreachable(); And this to _Rep::_M_is_leaked() and _Rep::_M_is_shared(): if (_S_empty_rep()._M_refcount != 0) __builtin_unreachable(); libstdc++-v3/ChangeLog: PR tree-optimization/107087 * include/bits/cow_string.h (basic_string::size()): Add optimizer hint that _S_empty_rep()._M_length is always zero. (basic_string::length()): Call size().
next prev parent reply other threads:[~2023-03-31 22:45 UTC|newest] Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-09-29 14:35 [Bug middle-end/107087] New: " redi at gcc dot gnu.org 2023-03-09 20:48 ` [Bug tree-optimization/107087] " redi at gcc dot gnu.org 2023-03-09 20:49 ` [Bug tree-optimization/107087] [13 Regression] " redi at gcc dot gnu.org 2023-03-15 10:00 ` rguenth at gcc dot gnu.org 2023-03-27 13:00 ` rguenth at gcc dot gnu.org 2023-03-27 13:52 ` rguenth at gcc dot gnu.org 2023-03-27 14:00 ` redi at gcc dot gnu.org 2023-03-28 13:25 ` cvs-commit at gcc dot gnu.org 2023-03-28 13:26 ` rguenth at gcc dot gnu.org 2023-03-30 8:31 ` redi at gcc dot gnu.org 2023-03-31 11:36 ` [Bug tree-optimization/107087] [12/13 " rguenth at gcc dot gnu.org 2023-03-31 11:55 ` redi at gcc dot gnu.org 2023-03-31 12:43 ` redi at gcc dot gnu.org 2023-03-31 22:45 ` cvs-commit at gcc dot gnu.org [this message] 2023-03-31 23:25 ` [Bug tree-optimization/107087] [12 " redi at gcc dot gnu.org 2023-04-27 11:50 ` rguenth at gcc dot gnu.org 2023-04-27 12:00 ` redi at gcc dot gnu.org 2023-04-29 0:41 ` sjames at gcc dot gnu.org 2023-04-29 6:56 ` redi at gcc dot gnu.org 2023-04-29 7:02 ` sjames at gcc dot gnu.org 2023-05-08 12:25 ` rguenth at gcc dot gnu.org
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