flo@xxxxxxxxx wrote: > Autoconf did not help me here automatically. But maybe i have to change > something in configure.ac? > So what is the "right way"? Use -D_GNU_SOURCE while compiling or add a > #define? I decided to add the #define, and it works. Thank you for your > explanation and help! It looks like you can just add the AC_USE_SYSTEM_EXTENSIONS macro somewhere early in your configure.ac to get a combined set of related checks. <http://www.gnu.org/software/autoconf/manual/html_node/Posix-Variants.html>. Alternatively, you could call AC_PROG_CC_C99 which would end up setting CC to gcc -std=gnu99, which in turn should cause _ISOC99_SOURCE to be defined. This may be a bigger hammer than you require, depending on how much C99 your code requires. <http://www.gnu.org/software/autoconf/manual/html_node/C-Compiler.html#index-AC_005fPROG_005fCC_005fC99-750> Brian
