http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48968
--- Comment #7 from eggert at gnu dot org 2012-06-01 21:19:16 UTC --- Created attachment 27546 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27546 alternate test case, for x86, showing "({anonymous}) might be clobbered" By compiling on x86 (as opposed to x86-64) and tweaking the source code a bit I got a different diagnostic "error: variable '({anonymous})' might be clobbered by 'longjmp' or 'vfork'" which may help indicate where the problem is. Uncompress and compile the attached program with: gcc -v -m32 -std=gnu99 -c -Werror=clobbered -g -O2 t.i and the output is: Using built-in specs. COLLECT_GCC=gcc Target: x86_64-unknown-linux-gnu Configured with: ../gcc-4.7.0/configure --prefix=/home/eggert/opt/Linux-x86_64/gcc-4.7.0 --disable-nls Thread model: posix gcc version 4.7.0 (GCC) COLLECT_GCC_OPTIONS='-v' '-m32' '-std=gnu99' '-c' '-Werror=clobbered' '-g' '-O2' '-mtune=generic' '-march=x86-64' /home/eggert/opt/Linux-x86_64/gcc-4.7.0/libexec/gcc/x86_64-unknown-linux-gnu/4.7.0/cc1 -fpreprocessed t.i -quiet -dumpbase t.i -m32 -mtune=generic -march=x86-64 -auxbase t -g -O2 -Werror=clobbered -std=gnu99 -version -o /tmp/cc9OhgtR.s GNU C (GCC) version 4.7.0 (x86_64-unknown-linux-gnu) compiled by GNU C version 4.7.0, GMP version 4.3.2, MPFR version 3.0.0, MPC version 0.8.3-dev GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 GNU C (GCC) version 4.7.0 (x86_64-unknown-linux-gnu) compiled by GNU C version 4.7.0, GMP version 4.3.2, MPFR version 3.0.0, MPC version 0.8.3-dev GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 Compiler executable checksum: 0b542ccc033bf565e8473ef2771f60ec t.i: In function 'read_char': t.i:14930:1: error: variable '({anonymous})' might be clobbered by 'longjmp' or 'vfork' [-Werror=clobbered] t.i:14930:1: error: variable '({anonymous})' might be clobbered by 'longjmp' or 'vfork' [-Werror=clobbered] t.i:14930:1: error: variable '({anonymous})' might be clobbered by 'longjmp' or 'vfork' [-Werror=clobbered] t.i:14930:1: error: variable '({anonymous})' might be clobbered by 'longjmp' or 'vfork' [-Werror=clobbered] cc1: some warnings being treated as errors