[Valgrind-users] valgrind and strspn behaviour change

[Emmanuel R. <emm...@er...>]

Hi all,

I'm having an issue running a application under valgrind.
The application runs fine without it, but some code has a different 
behaviour with valgrind.

I've managed to track and isolate the issue to the following piece (full 
example is attached as test.c) :
     //work4 = 0x e2 e3 d9
     //                     S  T  R
     if((offset = strspn((char*)work4, alphanumericOrNational)) != 
(unsigned) tulen - 1){
         printf("name+%d character 0x%.2X is not alphanumeric or 
national\n", offset + 1, work4[offset]);
     }
     else
     {
         printf("Ok.\n");
     }

(it's ebcdic characters).

I upgrade to the latest but i had the same issue in an older version :

[user@vm01 valgrind]$ valgrind --version
valgrind-3.13.0

If i'm using GCC :

[user@vm01 valgrind]$ gcc test.c -o test
[user@vm01 valgrind]$ ./test
0xe2e3d9
Ok.
Offset = 3
[user@vm01 valgrind]$ valgrind ./test
==23848== Memcheck, a memory error detector
==23848== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et 
al.
==23848== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright 
info
==23848== Command: ./test
==23848==
0xe2e3d9
name+1 character 0xE2 is not alphanumeric or national
Offset = 0
==23848==
==23848== HEAP SUMMARY:
==23848==     in use at exit: 0 bytes in 0 blocks
==23848==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==23848==
==23848== All heap blocks were freed -- no leaks are possible
==23848==
==23848== For counts of detected and suppressed errors, rerun with: -v
==23848== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

[user@vm01 valgrind]$ gcc -v
Using built-in specs.
COLLECT_GCC=/usr/bin/gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-redhat-linux/4.8.5/lto-wrapper
Target: x86_64-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man 
--infodir=/usr/share/info 
--with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-bootstrap 
--enable-shared --enable-threads=posix --enable-checking=release 
--with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions 
--enable-gnu-unique-object --enable-linker-build-id 
--with-linker-hash-style=gnu 
--enable-languages=c,c++,objc,obj-c++,java,fortran,ada,go,lto 
--enable-plugin --enable-initfini-array --disable-libgcj 
--with-isl=/builddir/build/BUILD/gcc-4.8.5-20150702/obj-x86_64-redhat-linux/isl-install 
--with-cloog=/builddir/build/BUILD/gcc-4.8.5-20150702/obj-x86_64-redhat-linux/cloog-install 
--enable-gnu-indirect-function --with-tune=generic --with-arch_32=x86-64 
--build=x86_64-redhat-linux
Thread model: posix
gcc version 4.8.5 20150623 (Red Hat 4.8.5-11) (GCC)

Same thing with clang :

[user@vm01 valgrind]$ clang test.c -o test
[user@vm01 valgrind]$ ./test
0xe2e3d9
Ok.
Offset = 3
[user@vm01 valgrind]$ valgrind ./test
==27955== Memcheck, a memory error detector
==27955== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et 
al.
==27955== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright 
info
==27955== Command: ./test
==27955==
0xe2e3d9
name+1 character 0xE2 is not alphanumeric or national
Offset = 0
==27955==
==27955== HEAP SUMMARY:
==27955==     in use at exit: 0 bytes in 0 blocks
==27955==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==27955==
==27955== All heap blocks were freed -- no leaks are possible
==27955==
==27955== For counts of detected and suppressed errors, rerun with: -v
==27955== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
[user@vm01 valgrind]$ clang --version
clang version 3.8.0 (http://llvm.org/git/clang.git 
81e96a3d20c4d1c3bdc6fdbc2a800d11f7347c7e) (http://llvm.org/git/llvm.git 
f5ab7a4dbb3061b17b6cc010e6b5fa802e913a52)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

I dont understand the change in behaviour due to valgrind. Is this a 
known issue or a bug?

Thanks!

Emmanuel Reynard