m4/pandora.warnings check for libcloog does not work reliably detect availability.

[coldtobi]

During building for Debian I figured out that there are currently some ports which have old gccs (4.6.3)* which seems still to look for libcloog-ppl0 while only libcloog-ppl1 is available.

This triggers some build failures for several architectures as configure comes to the conclusion:

checking whether it is safe to use -floop-parallelize-all... yes

but later gcc will tell that libcloog is not available:

plugin/innobase/pars/pars0lex.c: In function 'yy_get_previous_state':
plugin/innobase/pars/pars0lex.c:2232:26: sorry, unimplemented: Graphite loop optimizations can only be used if the libcloog-ppl0 package is installed
plugin/innobase/pars/pars0lex.l: In function 'string_append':
plugin/innobase/pars/pars0lex.l:62:1: sorry, unimplemented: Graphite loop optimizations can only be used if the libcloog-ppl0 package is installed
plugin/innobase/pars/pars0lex.c:2581: confused by earlier errors, bailing out
Preprocessed source stored into /tmp/ccLiPdWj.out file, please attach this to your bugreport.
make[4]: *** [plugin/innobase/pars/plugin_innobase_libpars_la-pars0lex.lo] Error 1

Here are some build logs that fails:
https://buildd.debian.org/status/fetch.php?pkg=drizzle&arch=powerpc&ver=1%3A7.1.36-stable-4&stamp=1370861331
https://buildd.debian.org/status/fetch.php?pkg=drizzle&arch=s390&ver=1%3A7.1.36-stable-4&stamp=1370882827
https://buildd.debian.org/status/fetch.php?pkg=drizzle&arch=s390x&ver=1%3A7.1.36-stable-4&stamp=1370877675

[Stewart Smith (stewart)]

In another package I solved this by having a build-dep of libcloog-ppl-dev - will that work for you?

[coldtobi (tobi-coldtobi)]

No that won't solve it. (libcloog-ppl-dev is already a dependency).

However, it turned out that the problem was with a certain gcc version, which was looking for libcloog-ppl0, but only libcloog-ppl1 was available (SONAME bumped). So gcc bailed out with that message. (s.a. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=712257)

But the m4 macro did not detect that, so the test for the safety to use -floop-parallelize-all is IMHO incomplete as it should actually try to compile/link a programm using that feature to see if that works.