I am trying to build like this: ./autogen.sh ./configure --enable-debug --enable-git-version --prefix=$HOME/.local/pacman CFLAGS=-g And I get during make: In file included from /usr/include/stdlib.h:24:0, from add.c:21: /usr/include/features.h:330:4: error: #warning _FORTIFY_SOURCE requires compiling with optimization (-O) [-Werror=cpp] cc1: all warnings being treated as errors Autoconf checks if FORTIFY_SOURCE works, but it does so without -Werror which is later used for compiling: # configure.ac if test "x$debug" = "xyes" ; then GCC_FORTIFY_SOURCE_CC WARNING_CFLAGS="-g -Wall -Werror" I attempted to fix this by considering WARNING_CFLAGS in GCC_FORTIFY_SOURCE_CC, but Autoconf is a mystery to me. In any case, it seems strange that _FORTIFY_SOURCE would be used only with debugging while the standard library warns about its use without optimization. Clemens