Bug 1287805

Summary:	-Wl,--as-needed ignored for -pthread
Product:	[Fedora] Fedora	Reporter:	Jaroslav Škarvada <jskarvad>
Component:	gcc	Assignee:	Jakub Jelinek <jakub>
Status:	CLOSED EOL	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	22	CC:	davejohansen, jakub, jwakely, law, mpolacek
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Hardware:	Unspecified
OS:	Unspecified
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Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2016-07-19 18:33:29 UTC	Type:	Bug
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Embargoed:

Description Jaroslav Škarvada 2015-12-02 17:48:03 UTC

Description of problem:
If gcc called as linker with -Wl,--as-needed followed by -pthread, the libpthread is added as unused direct dependency.

Version-Release number of selected component (if applicable):
gcc-5.1.1-4.fc22.x86_64

How reproducible:
Always

Steps to Reproduce:
1. gcc -Wl,--as-needed -shared -fPIC OBJ1 OBJ2 libtest.so
2. ldd -u ./libtest.so
3. gcc -Wl,--as-needed -shared -fPIC OBJ1 OBJ2 -pthread libtest.so
4. ldd -u ./libtest.so

Actual results:
Unused direct dependencies:
	/lib64/libpthread.so.0

Expected results:
No unused direct dependencies

Additional info:
I checked manual page, but it doesn't seem there is written that this shouldn't work.

Comment 1 Jonathan Wakely 2015-12-02 19:49:24 UTC

-pthread is not simply equivalent to -lpthread, so I wouldn't have expected it to work like that anyway.

If you want to link with "--as-needed -lpthread" then you can use that (in addition to -pthread if you want).

Note that for the C++ runtime library the current behaviour is useful, because the pthread symbols are only referenced through weak symbols, so --as-needed -pthread would fail to consider the symbols "needed" and would fail to link libpthread.so even when the code uses e.g std::mutex and libpthread is definitely needed.

Comment 2 Jaroslav Škarvada 2015-12-03 09:14:06 UTC

Please could you mention it in documentation (manual page)?

Comment 3 Fedora End Of Life 2016-07-19 18:33:29 UTC

Fedora 22 changed to end-of-life (EOL) status on 2016-07-19. Fedora 22 is
no longer maintained, which means that it will not receive any further
security or bug fix updates. As a result we are closing this bug.

If you can reproduce this bug against a currently maintained version of
Fedora please feel free to reopen this bug against that version. If you
are unable to reopen this bug, please file a new report against the
current release. If you experience problems, please add a comment to this
bug.

Thank you for reporting this bug and we are sorry it could not be fixed.