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From: "bruno at clisp dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/109990] [12/13/14 Regression] Bogus -Wuse-after-free warning after realloc Date: Fri, 26 May 2023 16:36:36 +0000 [thread overview] Message-ID: <bug-109990-4-2JR9wTCZ2C@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-109990-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109990 --- Comment #5 from Bruno Haible <bruno at clisp dot org> --- Created attachment 55170 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55170&action=edit test case bar2.c Find attached a modified test case. I changed the code to map[i].alias = new_pool + (map[i].alias - string_space); map[i].value = new_pool + (map[i].value - string_space); so that it subtracts pointers into the old string_space, producing an integer, and adding that integer to new_pool. It produces the same warning (even twice, apparently because there is no common subexpression between the two lines any more): $ gcc -Wall -O2 -S bar2.c bar2.c: In function ‘read_alias_file’: bar2.c:123:67: warning: pointer may be used after ‘realloc’ [-Wuse-after-free] 123 | map[i].value = new_pool + (map[i].value - string_space); | ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~ bar2.c:114:45: note: call to ‘realloc’ here 114 | char *new_pool = (char *) realloc (string_space, new_size); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ bar2.c:122:67: warning: pointer may be used after ‘realloc’ [-Wuse-after-free] 122 | map[i].alias = new_pool + (map[i].alias - string_space); | ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~ bar2.c:114:45: note: call to ‘realloc’ here 114 | char *new_pool = (char *) realloc (string_space, new_size); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
next prev parent reply other threads:[~2023-05-26 16:36 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-05-26 13:58 [Bug middle-end/109990] New: [12 " bruno at clisp dot org 2023-05-26 14:25 ` [Bug middle-end/109990] [12/13/14 " pinskia at gcc dot gnu.org 2023-05-26 14:30 ` pinskia at gcc dot gnu.org 2023-05-26 14:31 ` pinskia at gcc dot gnu.org 2023-05-26 16:27 ` bruno at clisp dot org 2023-05-26 16:36 ` bruno at clisp dot org [this message] 2023-05-26 16:39 ` pinskia at gcc dot gnu.org 2023-05-30 7:35 ` rguenth at gcc dot gnu.org 2024-03-10 3:37 ` law at gcc dot gnu.org 2024-03-22 13:45 ` law at gcc dot gnu.org
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