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From: "stefan at bytereef dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/98753] -Wfree-nonheap-object on unreachable code with -O0 Date: Tue, 02 Jan 2024 16:08:18 +0000 [thread overview] Message-ID: <bug-98753-4-nttYwBDXZM@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-98753-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98753 --- Comment #16 from Stefan Krah <stefan at bytereef dot org> --- I have encountered the same issue (gcc emits a false positive warning when free() is called conditionally) in the mpdecimal project when compiled with -flto. Worse, mpdecimal itself as well as a large test suite compile without warnings, so distributions will think everything is fine. Until a user uses the static libmpdec.a for a trivial program: wget https://www.bytereef.org/software/mpdecimal/releases/mpdecimal-2.5.1.tar.gz tar xvf mpdecimal-2.5.1.tar.gz cd mpdecimal-2.5.1 ./configure CFLAGS="-flto=auto" CXXFLAGS="-flto=auto" LDFLAGS="-flto=auto" LDXXFLAGS="-flto=auto" make # The trivial program: $ cd libmpdec $ make bench gcc -Wall -Wextra -Wno-unknown-pragmas -std=c99 -pedantic -DNDEBUG -O2 -flto=auto -o bench bench.c libmpdec.a -lm In function ‘mpd_del’, inlined from ‘_mpd_qaddsub.constprop’ at mpdecimal.c:3471:5: mpdecimal.c:470:9: warning: attempt to free a non-heap object ‘big_aligned’ [-Wfree-nonheap-object] mpd_free(dec); Here, the user will get a static library to which he may not even have the source code readily available and gets a false positive warning for code in that library. Like others, I think this warning should be under a category -Wmaybe and be less decisive in its message. For the next mpdecimal release the Makefile will filter out -flto for the static library build.
prev parent reply other threads:[~2024-01-02 16:08 UTC|newest] Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-01-19 20:18 [Bug c++/98753] New: -Wfree-nonheap-object on Bison generated code foss at grueninger dot de 2021-01-19 20:55 ` [Bug c++/98753] " msebor at gcc dot gnu.org 2021-01-20 5:22 ` akim.demaille at gmail dot com 2021-01-20 7:31 ` rguenth at gcc dot gnu.org 2021-01-20 7:40 ` foss at grueninger dot de 2021-01-20 16:48 ` msebor at gcc dot gnu.org 2021-01-20 17:00 ` foss at grueninger dot de 2021-01-20 17:34 ` [Bug middle-end/98753] -Wfree-nonheap-object on unreachable code with -O0 msebor at gcc dot gnu.org 2021-01-20 17:34 ` akim.demaille at gmail dot com 2021-01-20 17:40 ` akim.demaille at gmail dot com 2021-01-26 19:37 ` slyfox at gcc dot gnu.org 2021-01-29 11:29 ` boris at kolpackov dot net 2021-01-29 11:30 ` boris at kolpackov dot net 2021-01-29 11:30 ` boris at kolpackov dot net 2021-01-29 11:36 ` boris at kolpackov dot net 2021-01-29 16:48 ` msebor at gcc dot gnu.org 2024-01-02 16:08 ` stefan at bytereef dot org [this message]
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