Good catch - how long did that take to find? jon.
On Thu, Feb 10, 2011 at 6:06 AM, Eric Blake <ebl...@redhat.com> wrote: > Configuration Information [Automatically generated, do not change]: > Machine: x86_64 > OS: linux-gnu > Compiler: gcc > Compilation CFLAGS: -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' > -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-redhat-linux-gnu' > -DCONF_VENDOR='redhat' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' > -DSHELL -DHAVE_CONFIG_H -I. -I. -I./include -I./lib -D_GNU_SOURCE > -DRECYCLES_PIDS -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions > -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic > uname output: Linux office 2.6.35.10-74.fc14.x86_64 #1 SMP Thu Dec 23 > 16:04:50 UTC 2010 x86_64 x86_64 x86_64 GNU/Linux > Machine Type: x86_64-redhat-linux-gnu > > > Bash Version: 4.1 > Patch Level: 7 > Release Status: release > > Description: > There is a report of bash being miscompiled for cygwin when using gcc > 4.3.4 -O2, but succeeding when compiled with -O1: > http://cygwin.com/ml/cygwin/2011-02/msg00230.html > > Compiling with -Wextra reveals the culprit: > execute_cmd.c: In function ‘execute_function.clone.2’: > execute_cmd.c:4007:23: warning: variable ‘bash_source_a’ might be > clobbered by ‘longjmp’ or ‘vfork’ > execute_cmd.c:4007:39: warning: variable ‘bash_lineno_a’ might be > clobbered by ‘longjmp’ or ‘vfork’ > execute_cmd.c: In function ‘execute_in_subshell’: > execute_cmd.c:1296:12: warning: variable ‘tcom’ might be clobbered by > ‘longjmp’ or ‘vfork’ > > POSIX is clear that the value of an automatic variable changed between > setjmp() and the subsequent longjmp() is unspecified unless the variable > is marked volatile, but bash is violating this constraint and modifying > several variables that cannot reliably be restored. Depending on what > code transformations the compiler makes, this can lead to crashes; in > cygwin's case, it appears that mere execution of a trap return handler > can cause bash to corrupt its own stack. > > Repeat-By: > make > rm execute_cmd.o > make CFLAGS='-Wextra -O2' > > Fix: > --- execute_cmd.c.orig 2011-02-09 11:53:13.470850670 -0700 > +++ execute_cmd.c 2011-02-09 11:53:48.422939088 -0700 > @@ -1293,7 +1293,7 @@ > int user_subshell, return_code, function_value, should_redir_stdin, > invert; > int ois, user_coproc; > int result; > - COMMAND *tcom; > + COMMAND *volatile tcom; > > USE_VAR(user_subshell); > USE_VAR(user_coproc); > @@ -4004,7 +4004,7 @@ > char *debug_trap, *error_trap, *return_trap; > #if defined (ARRAY_VARS) > SHELL_VAR *funcname_v, *nfv, *bash_source_v, *bash_lineno_v; > - ARRAY *funcname_a, *bash_source_a, *bash_lineno_a; > + ARRAY *funcname_a, *volatile bash_source_a, *volatile bash_lineno_a; > #endif > FUNCTION_DEF *shell_fn; > char *sfile, *t; > > > -- > Eric Blake ebl...@redhat.com +1-801-349-2682 > Libvirt virtualization library http://libvirt.org > >
