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* [Bug c/112826] New: gcc rejects the valid code and reports undefined reference @ 2023-12-02 15:32 jwzeng at nuaa dot edu.cn 2023-12-02 15:43 ` [Bug c/112826] " arsen at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: jwzeng at nuaa dot edu.cn @ 2023-12-02 15:32 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112826 Bug ID: 112826 Summary: gcc rejects the valid code and reports undefined reference Product: gcc Version: 14.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: jwzeng at nuaa dot edu.cn Target Milestone: --- Hi, the following code seems valid. Gcc rejects it while clang accepts. Compiler explorer: https://godbolt.org/z/sPK9sYqc6 ```c $ cat test.c int* a(); static int b() { int *c = a();} int main() {} $ $ gcc test.c /tmp/cchtt1Nc.o:test.c:function b: error: undefined reference to 'a' collect2: error: ld returned 1 exit status $ $ clang test.c test.c:2:31: warning: non-void function does not return a value [-Wreturn-type] 2 | static int b() { int *c = a();} | ^ 1 warning generated. $ $ gcc --version gcc (GCC) 13.1.0 Copyright (C) 2023 Free Software Foundation, Inc. $ $ clang --version clang version 16.0.0 Target: x86_64-unknown-linux-gnu Thread model: posix ``` ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/112826] gcc rejects the valid code and reports undefined reference 2023-12-02 15:32 [Bug c/112826] New: gcc rejects the valid code and reports undefined reference jwzeng at nuaa dot edu.cn @ 2023-12-02 15:43 ` arsen at gcc dot gnu.org 2023-12-02 16:31 ` xry111 at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: arsen at gcc dot gnu.org @ 2023-12-02 15:43 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112826 Arsen Arsenović <arsen at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |arsen at gcc dot gnu.org --- Comment #1 from Arsen Arsenović <arsen at gcc dot gnu.org> --- I can't assert the validity of this code, but -O1 does elide the function as expected. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/112826] gcc rejects the valid code and reports undefined reference 2023-12-02 15:32 [Bug c/112826] New: gcc rejects the valid code and reports undefined reference jwzeng at nuaa dot edu.cn 2023-12-02 15:43 ` [Bug c/112826] " arsen at gcc dot gnu.org @ 2023-12-02 16:31 ` xry111 at gcc dot gnu.org 2023-12-02 22:43 ` pinskia at gcc dot gnu.org 2023-12-03 8:01 ` jwzeng at nuaa dot edu.cn 3 siblings, 0 replies; 5+ messages in thread From: xry111 at gcc dot gnu.org @ 2023-12-02 16:31 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112826 Xi Ruoyao <xry111 at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |INVALID Status|UNCONFIRMED |RESOLVED CC| |xry111 at gcc dot gnu.org --- Comment #2 from Xi Ruoyao <xry111 at gcc dot gnu.org> --- N1570 6.9 p2: "If an identifier declared with external linkage is used in an expression (other than as part of the operand of a sizeof or _Alignof operator whose result is an integer constant), somewhere in the entire program there shall be exactly one external definition for the identifier" and annex J.2 explicitly lists "An identifier with external linkage is used, but in the program there does not exist exactly one external definition for the identifier" as undefined behavior. Note that you cannot interpret "used" as "really executed at runtime" because it's impossible to solve halting problem, so such an "interpretation" will render the entire standard nonsense. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/112826] gcc rejects the valid code and reports undefined reference 2023-12-02 15:32 [Bug c/112826] New: gcc rejects the valid code and reports undefined reference jwzeng at nuaa dot edu.cn 2023-12-02 15:43 ` [Bug c/112826] " arsen at gcc dot gnu.org 2023-12-02 16:31 ` xry111 at gcc dot gnu.org @ 2023-12-02 22:43 ` pinskia at gcc dot gnu.org 2023-12-03 8:01 ` jwzeng at nuaa dot edu.cn 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2023-12-02 22:43 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112826 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- See Also| |https://gcc.gnu.org/bugzill | |a/show_bug.cgi?id=14105 --- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Note PR 14105 is the opposite request but both are invalid as both behavior with and without optimization is allowed by the C standard. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/112826] gcc rejects the valid code and reports undefined reference 2023-12-02 15:32 [Bug c/112826] New: gcc rejects the valid code and reports undefined reference jwzeng at nuaa dot edu.cn ` (2 preceding siblings ...) 2023-12-02 22:43 ` pinskia at gcc dot gnu.org @ 2023-12-03 8:01 ` jwzeng at nuaa dot edu.cn 3 siblings, 0 replies; 5+ messages in thread From: jwzeng at nuaa dot edu.cn @ 2023-12-03 8:01 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112826 --- Comment #4 from Junwei Zeng <jwzeng at nuaa dot edu.cn> --- Thank you for your explanation. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-12-03 8:01 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2023-12-02 15:32 [Bug c/112826] New: gcc rejects the valid code and reports undefined reference jwzeng at nuaa dot edu.cn 2023-12-02 15:43 ` [Bug c/112826] " arsen at gcc dot gnu.org 2023-12-02 16:31 ` xry111 at gcc dot gnu.org 2023-12-02 22:43 ` pinskia at gcc dot gnu.org 2023-12-03 8:01 ` jwzeng at nuaa dot edu.cn
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