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RFC: Bug 60749 - Do not need to link against -lm for fabs*()

DISCUSSION walter harms 2 participants 5 messages Sep 13, 2013 – Mar 10, 2014 4 messages not in the archive Man-pages: manual pages for Linux -- Sections 2, 3, 4, 5, and 7

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walter harms

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#0 lore raw

hi list,
i was investigating this and the good news it that you still need a libm. On the other side the reporter is right he does not need to specify that. Obviously this depends on the linker script used.

The math man pages say: "Link with -lm".
Perhaps it is better to say 'You may need to Link with -lm".

any comments on that ?

re,
wh
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#2 lore raw

Walter,

Quoted 9 lines · walter harms

hi list,
i was investigating this and the good news it that you still need a libm. On the other side the reporter is right he does not need to specify that. Obviously this depends on the linker script used.

The math man pages say: "Link with -lm".
Perhaps it is better to say 'You may need to Link with -lm".

any comments on that ?

Thanks for looking at this bug. Could you elaborate a little more on what it/sin't in the linker script that makes the difference?

Thanks,

Michael
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A message that is not in the archive (sent off-list or not yet received): CAKgNAkiy54SbGEt6KQ2a87SQejoyuzcTvDbVK8aAQXd==yNNvg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org

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#4 lore raw

Am 13.09.2013 20:20, schrieb Michael Kerrisk (man-pages):

Quoted 8 lines

Walter,

Quoted 5 lines · walter harms

hi list,
i was investigating this and the good news it that you still need a libm. On the other side the reporter is right he does not need to specify that. Obviously this depends on the linker script used.

Quoted 9 lines
Quoted 4 lines

The math man pages say: "Link with -lm".
Perhaps it is better to say 'You may need to Link with -lm".

any comments on that ?

Thanks for looking at this bug. Could you elaborate a little more on what it/sin't in the linker script that makes the difference?

I have no clue what linker magic is needed.

re,
wh

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A message that is not in the archive (sent off-list or not yet received): [email protected]

author
#6 lore raw

Am 14.09.2013 14:05, schrieb walter harms:

Quoted 14 lines

Am 13.09.2013 20:20, schrieb Michael Kerrisk (man-pages):

Quoted 11 lines

Walter,

Quoted 8 lines · walter harms

hi list,
i was investigating this and the good news it that you still need a libm. On the other side the reporter is right he does not need to specify that. Obviously this depends on the linker script used.

The math man pages say: "Link with -lm".
Perhaps it is better to say 'You may need to Link with -lm".

Quoted 9 lines
Quoted 6 lines
Quoted 1 line

any comments on that ?

Thanks for looking at this bug. Could you elaborate a little more on what it/sin't in the linker script that makes the difference?

I have no clue what linker magic is needed.

I know what it going on. the is no linker magic required.
The point is gcc build-ins. Some functions are replaced with build-ins. That happens e.g. with fabs() what the original poster noted. Disabling the build-ins with gcc -fno-builtin shows that the -lm is still a requirement.

next problem, who will do the bugzilla-entry ?

re,
wh

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#8 lore raw

Walter,

Quoted 24 lines · walter harms

Am 14.09.2013 14:05, schrieb walter harms:

Quoted 21 lines

Am 13.09.2013 20:20, schrieb Michael Kerrisk (man-pages):

Quoted 17 lines

Walter,

Quoted 9 lines · walter harms

hi list,
i was investigating this and the good news it that you still need a libm. On the other side the reporter is right he does not need to specify that. Obviously this depends on the linker script used.

The math man pages say: "Link with -lm".
Perhaps it is better to say 'You may need to Link with -lm".

any comments on that ?

Thanks for looking at this bug. Could you elaborate a little more on what it/sin't in the linker script that makes the difference?

Quoted 7 lines
Quoted 2 lines

I have no clue what linker magic is needed.

I know what it going on. the is no linker magic required.
The point is gcc build-ins. Some functions are replaced with build-ins. That happens e.g. with fabs() what the original poster noted. Disabling the build-ins with gcc -fno-builtin shows that the -lm is still a requirement.

Thanks! I hadn't thought of that. I see there is a list available in the gcc documentation at http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html

Quoted 1 line

next problem, who will do the bugzilla-entry ?

I will add something to https://bugzilla.kernel.org/show_bug.cgi?id=60749
Fundamentally, this is a gcc feature, and I don't think there's much that can be sensibly said about it in man-pages.

Cheers,

Michael

Signature · 7 lines
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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