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* [Bug middle-end/104436] New: spurious -Wdangling-pointer assigning local address to a class passed by value @ 2022-02-07 23:49 msebor at gcc dot gnu.org 2022-02-07 23:50 ` [Bug middle-end/104436] " msebor at gcc dot gnu.org ` (6 more replies) 0 siblings, 7 replies; 8+ messages in thread From: msebor at gcc dot gnu.org @ 2022-02-07 23:49 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104436 Bug ID: 104436 Summary: spurious -Wdangling-pointer assigning local address to a class passed by value Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: middle-end Assignee: unassigned at gcc dot gnu.org Reporter: msebor at gcc dot gnu.org Target Milestone: --- The test case below, reduced from https://bugzilla.redhat.com/show_bug.cgi?id=2051740, shows that -Wdangling-pointer can be made to trigger by assigning an object of a C++ class with a user-defined copy ctor that stores a pointer to a local in a function that takes an argument of the class by value. GCC transforms the by-value argument of the function to a by-reference, which is one of the use cases the warning is designed to detect. $ cat rhbz2051740.C && gcc -O1 -S -Wall -fdump-tree-optimized=/dev/stdout rhbz2051740.C struct S { S () = default; S (const S &s): p (s.p) { } void *p; }; void foo (S s) { int a[3]; S t; t.p = a; s = t; } rhbz2051740.C: In function ‘void foo(S)’: rhbz2051740.C:13:5: warning: storing the address of local variable ‘a’ in ‘*s.S::p’ [-Wdangling-pointer=] 13 | s = t; | ~~^~~ rhbz2051740.C:11:7: note: ‘a’ declared here 11 | int a[3]; | ^ rhbz2051740.C:11:7: note: ‘s’ declared here ;; Function foo (_Z3foo1S, funcdef_no=3, decl_uid=2396, cgraph_uid=4, symbol_order=3) void foo (struct S & s) { int a[3]; <bb 2> [local count: 1073741824]: s_2(D)->p = &a; a ={v} {CLOBBER}; return; } ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/104436] spurious -Wdangling-pointer assigning local address to a class passed by value 2022-02-07 23:49 [Bug middle-end/104436] New: spurious -Wdangling-pointer assigning local address to a class passed by value msebor at gcc dot gnu.org @ 2022-02-07 23:50 ` msebor at gcc dot gnu.org 2022-02-08 0:22 ` msebor at gcc dot gnu.org ` (5 subsequent siblings) 6 siblings, 0 replies; 8+ messages in thread From: msebor at gcc dot gnu.org @ 2022-02-07 23:50 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104436 Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Last reconfirmed| |2022-02-07 URL| |https://bugzilla.redhat.com | |/show_bug.cgi?id=2051740 Keywords| |diagnostic Ever confirmed|0 |1 Status|UNCONFIRMED |NEW Blocks| |104077 Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104077 [Bug 104077] bogus/missing -Wdangling-pointer ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/104436] spurious -Wdangling-pointer assigning local address to a class passed by value 2022-02-07 23:49 [Bug middle-end/104436] New: spurious -Wdangling-pointer assigning local address to a class passed by value msebor at gcc dot gnu.org 2022-02-07 23:50 ` [Bug middle-end/104436] " msebor at gcc dot gnu.org @ 2022-02-08 0:22 ` msebor at gcc dot gnu.org 2022-02-08 9:08 ` rguenth at gcc dot gnu.org ` (4 subsequent siblings) 6 siblings, 0 replies; 8+ messages in thread From: msebor at gcc dot gnu.org @ 2022-02-08 0:22 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104436 Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |msebor at gcc dot gnu.org --- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> --- It seems that DECL_BY_REFERENCE(fndecl) might be able to tell us if the argument is a "fake reference" that the by-value argument is substituted for. Let me see if that works. ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/104436] spurious -Wdangling-pointer assigning local address to a class passed by value 2022-02-07 23:49 [Bug middle-end/104436] New: spurious -Wdangling-pointer assigning local address to a class passed by value msebor at gcc dot gnu.org 2022-02-07 23:50 ` [Bug middle-end/104436] " msebor at gcc dot gnu.org 2022-02-08 0:22 ` msebor at gcc dot gnu.org @ 2022-02-08 9:08 ` rguenth at gcc dot gnu.org 2022-02-08 22:00 ` [Bug middle-end/104436] [12 Regression] " msebor at gcc dot gnu.org ` (3 subsequent siblings) 6 siblings, 0 replies; 8+ messages in thread From: rguenth at gcc dot gnu.org @ 2022-02-08 9:08 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104436 --- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- DECL_BY_REFERENCE on the PARM_DECL tells you that indeed (not on the fndecl). ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/104436] [12 Regression] spurious -Wdangling-pointer assigning local address to a class passed by value 2022-02-07 23:49 [Bug middle-end/104436] New: spurious -Wdangling-pointer assigning local address to a class passed by value msebor at gcc dot gnu.org ` (2 preceding siblings ...) 2022-02-08 9:08 ` rguenth at gcc dot gnu.org @ 2022-02-08 22:00 ` msebor at gcc dot gnu.org 2022-03-09 13:18 ` rguenth at gcc dot gnu.org ` (2 subsequent siblings) 6 siblings, 0 replies; 8+ messages in thread From: msebor at gcc dot gnu.org @ 2022-02-08 22:00 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104436 Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Target Milestone|--- |12.0 Summary|spurious -Wdangling-pointer |[12 Regression] spurious |assigning local address to |-Wdangling-pointer |a class passed by value |assigning local address to | |a class passed by value Keywords| |patch --- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> --- Patch: https://gcc.gnu.org/pipermail/gcc-patches/2022-February/590046.html ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/104436] [12 Regression] spurious -Wdangling-pointer assigning local address to a class passed by value 2022-02-07 23:49 [Bug middle-end/104436] New: spurious -Wdangling-pointer assigning local address to a class passed by value msebor at gcc dot gnu.org ` (3 preceding siblings ...) 2022-02-08 22:00 ` [Bug middle-end/104436] [12 Regression] " msebor at gcc dot gnu.org @ 2022-03-09 13:18 ` rguenth at gcc dot gnu.org 2022-03-15 0:27 ` cvs-commit at gcc dot gnu.org 2022-03-15 0:27 ` msebor at gcc dot gnu.org 6 siblings, 0 replies; 8+ messages in thread From: rguenth at gcc dot gnu.org @ 2022-03-09 13:18 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104436 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Priority|P3 |P1 ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/104436] [12 Regression] spurious -Wdangling-pointer assigning local address to a class passed by value 2022-02-07 23:49 [Bug middle-end/104436] New: spurious -Wdangling-pointer assigning local address to a class passed by value msebor at gcc dot gnu.org ` (4 preceding siblings ...) 2022-03-09 13:18 ` rguenth at gcc dot gnu.org @ 2022-03-15 0:27 ` cvs-commit at gcc dot gnu.org 2022-03-15 0:27 ` msebor at gcc dot gnu.org 6 siblings, 0 replies; 8+ messages in thread From: cvs-commit at gcc dot gnu.org @ 2022-03-15 0:27 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104436 --- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Martin Sebor <msebor@gcc.gnu.org>: https://gcc.gnu.org/g:373a2dc2be0089ae59b61202a6023458aaaf63d8 commit r12-7650-g373a2dc2be0089ae59b61202a6023458aaaf63d8 Author: Martin Sebor <msebor@redhat.com> Date: Mon Mar 14 18:23:08 2022 -0600 Avoid -Wdangling-pointer for by-transparent-reference arguments [PR104436]. This change avoids -Wdangling-pointer for by-value arguments transformed into by-transparent-reference. Resolves: PR middle-end/104436 - spurious -Wdangling-pointer assigning local address to a class passed by value gcc/ChangeLog: PR middle-end/104436 * gimple-ssa-warn-access.cc (pass_waccess::check_dangling_stores): Check for warning suppression. Avoid by-value arguments transformed into by-transparent-reference. gcc/testsuite/ChangeLog: PR middle-end/104436 * c-c++-common/Wdangling-pointer-8.c: New test. * g++.dg/warn/Wdangling-pointer-5.C: New test. ^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/104436] [12 Regression] spurious -Wdangling-pointer assigning local address to a class passed by value 2022-02-07 23:49 [Bug middle-end/104436] New: spurious -Wdangling-pointer assigning local address to a class passed by value msebor at gcc dot gnu.org ` (5 preceding siblings ...) 2022-03-15 0:27 ` cvs-commit at gcc dot gnu.org @ 2022-03-15 0:27 ` msebor at gcc dot gnu.org 6 siblings, 0 replies; 8+ messages in thread From: msebor at gcc dot gnu.org @ 2022-03-15 0:27 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104436 Martin Sebor <msebor at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |FIXED Status|ASSIGNED |RESOLVED --- Comment #5 from Martin Sebor <msebor at gcc dot gnu.org> --- Fixed in r12-7650. ^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2022-03-15 0:27 UTC | newest] Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-02-07 23:49 [Bug middle-end/104436] New: spurious -Wdangling-pointer assigning local address to a class passed by value msebor at gcc dot gnu.org 2022-02-07 23:50 ` [Bug middle-end/104436] " msebor at gcc dot gnu.org 2022-02-08 0:22 ` msebor at gcc dot gnu.org 2022-02-08 9:08 ` rguenth at gcc dot gnu.org 2022-02-08 22:00 ` [Bug middle-end/104436] [12 Regression] " msebor at gcc dot gnu.org 2022-03-09 13:18 ` rguenth at gcc dot gnu.org 2022-03-15 0:27 ` cvs-commit at gcc dot gnu.org 2022-03-15 0:27 ` msebor at gcc dot gnu.org
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