[tlbuild] Bug in libpng affecting Solaris 10

[Mojca Miklavec]

On 19 January 2016 at 02:28, Karl Berry wrote:
>         https://sourceforge.net/p/libpng/bugs/245/
>
> What a mess.
>
> How about compiling with gcc 4.9 (or any other working version)?  I too
> have found places (dvisvgm...) where compiler version x on os version y
> fails with package z.  My workaround has been to use different versions.
>
> Also, gcc 5.3.0 is out.  Maybe it got fixed.  (Such a gratuitious
> bombing out seems completely unnecessary to me in the first place.)
>
> As for "how to change the version of the compiler", you can download the
> gcc+library sources and build it yourself in your home directory.  I can
> give you a (semi-)script if you want.  I know it's far from trivial, but
> then, changing the build system is not trivial either.
>
>     export CPPFLAGS="-D_XOPEN_SOURCE=600 -D__EXTENSIONS__"
>     someone perhaps add these flags (only for libpng and only for Solaris)
>     as a temporary workaround?
>
> 1) I don't recall anywhere else in the build tree that we have ever
> added system-specific options for a particular package.  Am I forgetting
> somewhere?  Probably ...
>
> 2) Apparently the problem is on "Solaris 5.10", rather than "Solaris",
> from your last additions to the thread?
>
> 3) Apparently the libpng author is not inclined to deal with this, so
> it's not clear that any such change would be temporary, which makes me
> want to find some other solution.
>
> 4) These options have far-reaching effects.  Using them worries me.
>
> 5) The specifics of the original problem remain unclear to me.  Here's a
> possible method for debugging further:
>
> Take that gcc invocation as output by libtool, add -dD, redirect the
> output to /tmp/foo, and run it (by hand) in the shell.  Then /tmp/foo
> should have the result of preprocessing (up to the point of error),
> including all the #defines as they are made.  Then it should be possible
> to determine what is defining the problematic symbols, and then perhaps
> there will be another way to avoid defining them in the first place.
>
> It may be necessary to remove the
>   -MT png.lo -MD -MP -MF .deps/png.Tpo
> from the invocation.  I'm not sure how all those dependency-generation
> flags interact with -d.  The gcc manual claims it should be fine, I
> think, but ...

I did that, but I didn't manage to get anything useful out of it at
all. I didn't get any additional output other than the error already
quoted in the bug report.

Meanwhile I came up with a minimal example that fails to compile:

#define _POSIX_SOURCE 1
#include <stdio.h>
void main() {}

I managed to compile libpng if I remove
    #define _POSIX_SOURCE 1
from three files (pngpriv.h, pngtest.c, contrib/libtests/pngvalid.c).

Mojca