[Bug c/64187] New: Writing to a char array cast from a char * causes a segmentation fault

[Bug c/64187] New: Writing to a char array cast from a char * causes a segmentation fault

[brian.corriveau at ericsson dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64187

            Bug ID: 64187
           Summary: Writing to a char array cast from a char * causes a
                    segmentation fault
           Product: gcc
           Version: 4.3.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: brian.corriveau at ericsson dot com

Created attachment 34193
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34193&action=edit
sample that produces segmentation fault

I was trying to work around a coverity optional data[0] overrun issue when I
came across this problem.

The code casts a char * to a char (*)[200], and tries to write to it. This
causes a segmentation fault.

System:
:~/src[1050]uname -a
Linux eussjlxxen204 2.6.32.45-0.3-xen #1 SMP 2011-08-22 10:12:58 +0200 x86_64
x86_64 x86_64 GNU/Linux

Here is the compiler output:

gcc -v -save-temps -g array.c
Using built-in specs.
Target: x86_64-suse-linux
Configured with: ../configure --prefix=/usr --infodir=/usr/share/info
--mandir=/usr/share/man --libdir=/usr/lib64 --libexecdir=/usr/lib64
--enable-languages=c,c++,objc,fortran,obj-c++,java,ada
--enable-checking=release --with-gxx-include-dir=/usr/include/c++/4.3
--enable-ssp --disable-libssp --with-bugurl=http://bugs.opensuse.org/
--with-pkgversion='SUSE Linux' --disable-libgcj --disable-libmudflap
--with-slibdir=/lib64 --with-system-zlib --enable-__cxa_atexit
--enable-libstdcxx-allocator=new --disable-libstdcxx-pch
--enable-version-specific-runtime-libs --program-suffix=-4.3
--enable-linux-futex --without-system-libunwind --with-cpu=generic
--build=x86_64-suse-linux
Thread model: posix
gcc version 4.3.4 [gcc-4_3-branch revision 152973] (SUSE Linux)
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-g' '-mtune=generic'
 /usr/lib64/gcc/x86_64-suse-linux/4.3/cc1 -E -quiet -v array.c -mtune=generic
-fworking-directory -fpch-preprocess -o array.i
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /usr/lib64/gcc/x86_64-suse-linux/4.3/include
 /usr/lib64/gcc/x86_64-suse-linux/4.3/include-fixed
 /usr/lib64/gcc/x86_64-suse-linux/4.3/../../../../x86_64-suse-linux/include
 /usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-g' '-mtune=generic'
 /usr/lib64/gcc/x86_64-suse-linux/4.3/cc1 -fpreprocessed array.i -quiet
-dumpbase array.c -mtune=generic -auxbase array -g -version -o array.s
GNU C (SUSE Linux) version 4.3.4 [gcc-4_3-branch revision 152973]
(x86_64-suse-linux)
        compiled by GNU C version 4.3.4 [gcc-4_3-branch revision 152973], GMP
version 4.2.3, MPFR version 2.3.2.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 91a878d77972b76d647d592fefc786fc
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-g' '-mtune=generic'
 /usr/lib64/gcc/x86_64-suse-linux/4.3/../../../../x86_64-suse-linux/bin/as -V
-Qy -o array.o array.s
GNU assembler version 2.20.0 (x86_64-suse-linux) using BFD version (GNU
Binutils; SUSE Linux Enterprise 11) 2.20.0.20100122-0.7.9
COMPILER_PATH=/usr/lib64/gcc/x86_64-suse-linux/4.3/:/usr/lib64/gcc/x86_64-suse-linux/4.3/:/usr/lib64/gcc/x86_64-suse-linux/:/usr/lib64/gcc/x86_64-suse-linux/4.3/:/usr/lib64/gcc/x86_64-suse-linux/:/usr/lib64/gcc/x86_64-suse-linux/4.3/../../../../x86_64-suse-linux/bin/
LIBRARY_PATH=/usr/lib64/gcc/x86_64-suse-linux/4.3/:/usr/lib64/gcc/x86_64-suse-linux/4.3/../../../../lib64/:/lib/../lib64/:/usr/lib/../lib64/:/usr/lib64/gcc/x86_64-suse-linux/4.3/../../../../x86_64-suse-linux/lib/:/usr/lib64/gcc/x86_64-suse-linux/4.3/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-g' '-mtune=generic'
 /usr/lib64/gcc/x86_64-suse-linux/4.3/collect2 --build-id --eh-frame-hdr -m
elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2
/usr/lib64/gcc/x86_64-suse-linux/4.3/../../../../lib64/crt1.o
/usr/lib64/gcc/x86_64-suse-linux/4.3/../../../../lib64/crti.o
/usr/lib64/gcc/x86_64-suse-linux/4.3/crtbegin.o
-L/usr/lib64/gcc/x86_64-suse-linux/4.3
-L/usr/lib64/gcc/x86_64-suse-linux/4.3/../../../../lib64 -L/lib/../lib64
-L/usr/lib/../lib64
-L/usr/lib64/gcc/x86_64-suse-linux/4.3/../../../../x86_64-suse-linux/lib
-L/usr/lib64/gcc/x86_64-suse-linux/4.3/../../.. array.o -lgcc --as-needed
-lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed
/usr/lib64/gcc/x86_64-suse-linux/4.3/crtend.o
/usr/lib64/gcc/x86_64-suse-linux/4.3/../../../../lib64/crtn.o

Run output:
:~/src[1047]./a.out
hEllo
Segmentation fault

[Bug c/64187] Writing to a char array cast from a char * causes a segmentation fault

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64187

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
    char *test = "this is a test";


This is a string literal so it stored in constant memory and which is why you
are getting a segfault.

[Bug c/64187] Writing to a char array cast from a char * causes a segmentation fault

[brian.corriveau at ericsson dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64187

--- Comment #2 from Brian <brian.corriveau at ericsson dot com> ---
(In reply to Andrew Pinski from comment #1)
>     char *test = "this is a test";
> 
> 
> This is a string literal so it stored in constant memory and which is why
> you are getting a segfault.

I was thinking "test" would be on the stack, but obviously not.

I did compile with the -Wall option before filing the bug, but I didn't get any
complaints. Maybe this is something that could be improved.

thanks for the speedy answer,
brian

[Bug c/64187] Writing to a char array cast from a char * causes a segmentation fault

[brian.corriveau at ericsson dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64187

--- Comment #3 from Brian <brian.corriveau at ericsson dot com> ---
Thanks for the speedy reply. I just added a comment on the bug. Maybe 
-Wall should catch this kind of thing?

thanks again
brian

pinskia at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64187
>
> Andrew Pinski <pinskia at gcc dot gnu.org> changed:
>
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>              Status|UNCONFIRMED                 |RESOLVED
>          Resolution|---                         |INVALID
>
> --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
>     char *test = "this is a test";
>
>
> This is a string literal so it stored in constant memory and which is why you
> are getting a segfault.
>
>