flac dev - Mar 2011 - pkg-config output and <FLAC/assert.h>

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?

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

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'm subscribed to this list. No need to CC me.

Paul Davis wrote:
> 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've now taken to doing the following in my configure.ac file:

    PKG_CHECK_MOD_VERSION(FLAC, flac >= 1.2.1, ac_cv_flac=yes, ac_cv_flac=no)
    # Make sure the FLAC_CFLAGS value is sane, strip trailing '/FLAC'.
    FLAC_CFLAGS=`echo $FLAC_CLFAGS | $SED "s/FLAC$//"`

Solve the problem for me and will still work when the flac.pc
file is fixed.

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

> 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>