Description of problem:
Rebuilding mksh using GCC 4.6 causes cc in permanent 99.9% CPU usage, the CPU
usage from the mockbuild in koji was told me by Jesse after requesting it.

[...]
cc -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -fno-strict-aliasing -fstack-protector-all -fwrapv -std=gnu99 -Wall -I.  -D_GNU_SOURCE -DHAVE_ATTRIBUTE_BOUNDED=0 -DHAVE_ATTRIBUTE_FORMAT=1 -DHAVE_ATTRIBUTE_NONNULL=1 -DHAVE_ATTRIBUTE_NORETURN=1 -DHAVE_ATTRIBUTE_UNUSED=1 -DHAVE_ATTRIBUTE_USED=1 -DHAVE_SYS_PARAM_H=1 -DHAVE_SYS_MKDEV_H=0 -DHAVE_SYS_MMAN_H=1 -DHAVE_SYS_SYSMACROS_H=1 -DHAVE_LIBGEN_H=1 -DHAVE_LIBUTIL_H=0 -DHAVE_PATHS_H=1 -DHAVE_STDBOOL_H=1 -DHAVE_STRINGS_H=1 -DHAVE_GRP_H=1 -DHAVE_ULIMIT_H=1 -DHAVE_VALUES_H=1 -DHAVE_STDINT_H=1 -DHAVE_RLIM_T=1 -DHAVE_SIG_T=1 -DHAVE_SYS_SIGNAME=0 -DHAVE_SYS_SIGLIST=1 -DHAVE_STRSIGNAL=0 -DHAVE_ARC4RANDOM=0 -DHAVE_ARC4RANDOM_PUSHB=0 -DHAVE_GETRUSAGE=1 -DHAVE_KILLPG=1 -DHAVE_MKNOD=1 -DHAVE_MKSTEMP=1 -DHAVE_NICE=1 -DHAVE_REVOKE=0 -DHAVE_SETLOCALE_CTYPE=1 -DHAVE_LANGINFO_CODESET=1 -DHAVE_SETMODE=0 -DHAVE_SETRESUGID=1 -DHAVE_SETGROUPS=1 -DHAVE_STRCASESTR=1 -DHAVE_STRLCPY=0 -DHAVE_ARC4RANDOM_DECL=1 -DHAVE_ARC4RANDOM_PUSHB_DECL=1 -DHAVE_FLOCK_DECL=0 -DHAVE_REVOKE_DECL=1 -DHAVE_SYS_SIGLIST_DECL=1 -DHAVE_PERSISTENT_HISTORY=1 -DHAVE_CONFIG_H -DCONFIG_H_FILENAME=\"sh.h\" -c lex.c
[never comes back, koji/mock timeout kills the process after a long time]

As this worked with older GCC versions fine, I feel this could be a bug in
our new GCC 4.6 - that's the only really new involved/changed component...

Version-Release number of selected component (if applicable):
gcc-4.6.0-0.6.fc15
mksh-39c-5.fc15

How reproducible:
Everytime, fire a scratch build in the Fedora buildsystem for example.

Actual results:
No successful rebuild.

Expected results:
Successful rebuild.