GNU bug report logs - #17294
Bug - nm_test_func check is confused with -flto

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Martin Liška <mliska <at> suse.cz>
To: bug-libtool <at> gnu.org
Subject: Bug - nm_test_func check is confused with -flto
Date: Fri, 18 Apr 2014 15:01:51 +0200

Hello,
    starting with GCC 4.9.0, compiler will use just slim objects files 
during LTO compilation. That means, no assembly output is put to object 
files. I noticed that libtool uses nm tools to extract symbol from 
object file: http://pastebin.com/RF1VubdR. Would it be possible to add 
-fno-lto for this check?

I think there should be added '-fno-lto' at line 14:
  (eval $ac_compile -fno-lto) 2>&5

What do you think about that?

Thank you,
Martin

Message #8 received at 17294 <at> debbugs.gnu.org (full text, mbox):

From: Peter Rosin <peda <at> lysator.liu.se>
To: Martin Liška <mliska <at> suse.cz>, 17294 <at> debbugs.gnu.org
Subject: Re: bug#17294: Bug - nm_test_func check is confused with -flto
Date: Sat, 17 May 2014 02:46:06 +0200

On 2014-04-18 15:01, Martin Liška wrote:
> Hello,
>     starting with GCC 4.9.0, compiler will use just slim objects files during LTO compilation. That means, no assembly output is put to object files. I noticed that libtool uses nm tools to extract symbol from object file: http://pastebin.com/RF1VubdR. Would it be possible to add -fno-lto for this check?
> 
> I think there should be added '-fno-lto' at line 14:
>   (eval $ac_compile -fno-lto) 2>&5
> 
> What do you think about that?

Hi, and sorry for the late response.

I think that it is not possible to blindly add -fno-lto without knowing
if the compiler understands -fno-lto.

Changing this takes more effort, sorry.

Cheers,
Peter

Message #11 received at 17294 <at> debbugs.gnu.org (full text, mbox):

From: Martin Liška <mliska <at> suse.cz>
To: Peter Rosin <peda <at> lysator.liu.se>, 17294 <at> debbugs.gnu.org
Subject: Re: bug#17294: Bug - nm_test_func check is confused with -flto
Date: Tue, 20 May 2014 13:32:02 +0200

On 05/17/2014 02:46 AM, Peter Rosin wrote:
> On 2014-04-18 15:01, Martin Liška wrote:
>> Hello,
>>      starting with GCC 4.9.0, compiler will use just slim objects files during LTO compilation. That means, no assembly output is put to object files. I noticed that libtool uses nm tools to extract symbol from object file: http://pastebin.com/RF1VubdR. Would it be possible to add -fno-lto for this check?
>>
>> I think there should be added '-fno-lto' at line 14:
>>    (eval $ac_compile -fno-lto) 2>&5
>>
>> What do you think about that?
> Hi, and sorry for the late response.
>
> I think that it is not possible to blindly add -fno-lto without knowing
> if the compiler understands -fno-lto.
>
> Changing this takes more effort, sorry.
>
> Cheers,
> Peter
>

Hello,
   I understand that suggested option is probably simple. How can we 
decorate some LTO sensitive checks with -flto if supported by a compiler?

Thanks,
Martin

Message #14 received at 17294 <at> debbugs.gnu.org (full text, mbox):

From: Martin Liška <mliska <at> suse.cz>
To: Peter Rosin <peda <at> lysator.liu.se>, 17294 <at> debbugs.gnu.org
Subject: Re: bug#17294: Bug - nm_test_func check is confused with -flto
Date: Wed, 04 Jun 2014 11:15:39 +0200

On 05/17/2014 02:46 AM, Peter Rosin wrote:
> On 2014-04-18 15:01, Martin Liška wrote:
>> Hello,
>>      starting with GCC 4.9.0, compiler will use just slim objects files during LTO compilation. That means, no assembly output is put to object files. I noticed that libtool uses nm tools to extract symbol from object file: http://pastebin.com/RF1VubdR. Would it be possible to add -fno-lto for this check?
>>
>> I think there should be added '-fno-lto' at line 14:
>>    (eval $ac_compile -fno-lto) 2>&5
>>
>> What do you think about that?
> Hi, and sorry for the late response.
>
> I think that it is not possible to blindly add -fno-lto without knowing
> if the compiler understands -fno-lto.
Hello Peter,
    I would appreciate any kind of help connected to configure script to be able to support -flto.

My suggestion:
1) we can detect if a compiler supports -flto
2) if so, we can define $ac_compile_without_lto = "$ac_compile -fno-lto"
3) otherwise, $ac_compile_without_lto = $ac_compile

What do you think about it?
Today, I found out another packages suffering from the same problem.

Thanks,
Martin
>
> Changing this takes more effort, sorry.
>
> Cheers,
> Peter
>

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