flac dev - Apr 2012 - pkg-config output and <FLAC/assert.h>

> From: Paul Davis <paul at linuxaudiosystems.com>
> To: flac-dev at xiph.org
> Cc: 
> Sent: Friday, March 25, 2011 5:39 AM
> Subject: Re: [Flac-dev] pkg-config output and <FLAC/assert.h>
> 
> On Fri, Mar 25, 2011 at 5:32 AM, Erik de Castro Lopo
> <mle+la at mega-nerd.com> wrote:
>>  Hi,
>> 
>>  FLAC helpfully provides a flac.pc file. Unfortunately there is a
>>  nasty interaction between that file and system header files.
>> 
>>  If ones installs flac and relies on pkg-config to find the CFLAGS
>>  one woulf get CFLAGS value of "-I${includedir}/FLAC" which 
> suggests
>>  that FLAC header files like <metadata.h> should be included as:
>> 
>>  ? ?#include <metadata.h>
>> 
>>  However, FLAC also ships an <assert.h> header file. If one
writes
>>  code that wants needs both the Standard C <assert.h> and the
FLAC
>>  header files, we run into a problem, the C compiler finds FLAC's
>>  <assert.h> instead of the Standard C version.
>> 
>>  I believe the correct solution to this problem is the change the
>>  Cflag value in flac.pc to "-I${includedir}" and then
encourage
>>  people to use:
>> 
>>  ? ?#include <FLAC/metadata.h>
>>  ? ?#include <FLAC/assert.h>
>>  ? ?#include <assert.h>
>> 
>>  which will no longer conflict.
>> 
>>  Opinions?
> 
> i recall raising this as an issue about 18 months ago. i certainly
> feel that the include style that flac uses now is simply wrong, and
> that your suggestion above (which matches the one i made) is
> substantially preferable.
I didn't follow, which style is wrong?? I never liked lazy search paths
like:

-I.../include/FLAC
#include <metadata.h>

because of the potential for conflict with other headers.? The code
should be using this style everywhere:

-I.../include
#include <FLAC/metadata.h>

Then there is no problem with
#include <FLAC/assert.h>

Josh Coalson wrote:
> > From: Paul Davis <paul at linuxaudiosystems.com>
> > To: flac-dev at xiph.org
> > Cc: 
> > Sent: Friday, March 25, 2011 5:39 AM
> > Subject: Re: [Flac-dev] pkg-config output and <FLAC/assert.h>
> > 
> > On Fri, Mar 25, 2011 at 5:32 AM, Erik de Castro Lopo
> > <mle+la at mega-nerd.com> wrote:
> >>  Hi,
> >> 
> >>  FLAC helpfully provides a flac.pc file. Unfortunately there is a
> >>  nasty interaction between that file and system header files.
> >> 
> >>  If ones installs flac and relies on pkg-config to find the CFLAGS
> >>  one woulf get CFLAGS value of "-I${includedir}/FLAC"
which
> > suggests
> >>  that FLAC header files like <metadata.h> should be included
as:
> >> 
> >>  ? ?#include <metadata.h>
> >> 
> >>  However, FLAC also ships an <assert.h> header file. If one
writes
> >>  code that wants needs both the Standard C <assert.h> and
the FLAC
> >>  header files, we run into a problem, the C compiler finds
FLAC's
> >>  <assert.h> instead of the Standard C version.
> >> 
> >>  I believe the correct solution to this problem is the change the
> >>  Cflag value in flac.pc to "-I${includedir}" and then
encourage
> >>  people to use:
> >> 
> >>  ? ?#include <FLAC/metadata.h>
> >>  ? ?#include <FLAC/assert.h>
> >>  ? ?#include <assert.h>
> >> 
> >>  which will no longer conflict.
> >> 
> >>  Opinions?
> > 
> > i recall raising this as an issue about 18 months ago. i certainly
> > feel that the include style that flac uses now is simply wrong, and
> > that your suggestion above (which matches the one i made) is
> > substantially preferable.
> 
> I didn't follow, which style is wrong?? I never liked lazy search paths
like:
> 
> -I.../include/FLAC
> #include <metadata.h>
> 
> because of the potential for conflict with other headers.? The code
> should be using this style everywhere:
> 
> -I.../include
> #include <FLAC/metadata.h>
> 
> Then there is no problem with
> #include <FLAC/assert.h>
Correct.

The problem is that currently the pkg-config shipped with most distros
(ie from the last release) gives this:

    $ pkg-config --cflags flac
    -I/usr/include/FLAC 

This encourages people in client code to do:

    #include <all.h>

which obviously has the potential to cause problems.

Instead pkg-config should give:

    $ pkg-config --cflags flac
    -I/usr/include/FLAC 

so that client code can do:

    #include <FLAC/all.h>

I'll submit a patch to fix this.

Cheers,
Erik
-- 
----------------------------------------------------------------------
Erik de Castro Lopo
http://www.mega-nerd.com/

Erik de Castro Lopo wrote:
> The problem is that currently the pkg-config shipped with most distros
> (ie from the last release) gives this:
> 
>     $ pkg-config --cflags flac
>     -I/usr/include/FLAC 
> 
> This encourages people in client code to do:
> 
>     #include <all.h>
> 
> which obviously has the potential to cause problems.
> 
> Instead pkg-config should give:
> 
>     $ pkg-config --cflags flac
>     -I/usr/include/FLAC 
> 
> so that client code can do:
> 
>     #include <FLAC/all.h>
> 
> I'll submit a patch to fix this.

Actually, thats already been fixed in Git:

commit 7ae181f27c16e7eca45840ec9171b938b9f86fbc
Author: Josh Coalson <jcoalson at users.sourceforce.net>
Date:   Sat Nov 29 20:56:09 2008 +0000

    remove /FLAC++ suffix on include path

commit b76d4f817c54c6fcfcb82fe72e38660c1b480774
Author: Josh Coalson <jcoalson at users.sourceforce.net>
Date:   Sat Nov 29 20:55:52 2008 +0000

    remove /FLAC suffix on include path


Erik
-- 
----------------------------------------------------------------------
Erik de Castro Lopo
http://www.mega-nerd.com/