Memory debugging-valgrind tool detects array access errors and memory leaks, valgrind leaks

Memory debugging-valgrind tool detects array access errors and memory leaks, valgrind leaks

The following C program allocates 1024 bytes of memory, reads data from areas outside the allocated memory, writes data after the end of the allocated memory, and finally makes the memory area inaccessible.

#include <stdio.h>#include <stdlib.h>int main(){    char *ptr = (char *)malloc( 1024 );    char ch;    //Uninitialized read    ch = ptr[1024];    //Write beyond the block    ptr[1024] = 0;    //Orphan the block    ptr = 0;    return 0;}

The following is the result of the valgrind tool: All the memory management errors are detected.

[zhang@localhost document]$ valgrind --leak-check=yes -v ./checker==19044== Memcheck, a memory error detector==19044== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.==19044== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info==19044== Command: ./checker==19044== --19044-- Valgrind options:--19044--    --leak-check=yes--19044--    -v--19044-- Contents of /proc/version:--19044--   Linux version 2.6.32-504.3.3.el6.x86_64 (mockbuild@c6b8.bsys.dev.centos.org) (gcc version 4.4.7 20120313 (Red Hat 4.4.7-11) (GCC) ) #1 SMP Wed Dec 17 01:55:02 UTC 2014--19044-- Arch and hwcaps: AMD64, LittleEndian, amd64-cx16-rdtscp-sse3-avx--19044-- Page sizes: currently 4096, max supported 4096--19044-- Valgrind library directory: /usr/local/lib/valgrind--19044-- Reading syms from /home/zhang/document/checker--19044-- Reading syms from /usr/local/lib/valgrind/memcheck-amd64-linux--19044--    object doesn't have a dynamic symbol table--19044-- Reading syms from /lib64/ld-2.12.so--19044-- Scheduler: using generic scheduler lock implementation.--19044-- Reading suppressions file: /usr/local/lib/valgrind/default.supp==19044== embedded gdbserver: reading from /tmp/vgdb-pipe-from-vgdb-to-19044-by-zhang-on-localhost.localdomain==19044== embedded gdbserver: writing to   /tmp/vgdb-pipe-to-vgdb-from-19044-by-zhang-on-localhost.localdomain==19044== embedded gdbserver: shared mem   /tmp/vgdb-pipe-shared-mem-vgdb-19044-by-zhang-on-localhost.localdomain==19044== ==19044== TO CONTROL THIS PROCESS USING vgdb (which you probably==19044== don't want to do, unless you know exactly what you're doing,==19044== or are doing some strange experiment):==19044==   /usr/local/lib/valgrind/../../bin/vgdb --pid=19044 ...command...==19044== ==19044== TO DEBUG THIS PROCESS USING GDB: start GDB like this==19044==   /path/to/gdb ./checker==19044== and then give GDB the following command==19044==   target remote | /usr/local/lib/valgrind/../../bin/vgdb --pid=19044==19044== --pid is optional if only one valgrind process is running==19044== --19044-- REDIR: 0x3283e17610 (ld-linux-x86-64.so.2:strlen) redirected to 0x38051201 (vgPlain_amd64_linux_REDIR_FOR_strlen)--19044-- Reading syms from /usr/local/lib/valgrind/vgpreload_core-amd64-linux.so--19044-- Reading syms from /usr/local/lib/valgrind/vgpreload_memcheck-amd64-linux.so==19044== WARNING: new redirection conflicts with existing -- ignoring it--19044--     old: 0x3283e17610 (strlen              ) R-> (0000.0) 0x38051201 vgPlain_amd64_linux_REDIR_FOR_strlen--19044--     new: 0x3283e17610 (strlen              ) R-> (2007.0) 0x04a08960 strlen--19044-- REDIR: 0x3283e17480 (ld-linux-x86-64.so.2:index) redirected to 0x4a08540 (index)--19044-- REDIR: 0x3283e17500 (ld-linux-x86-64.so.2:strcmp) redirected to 0x4a09320 (strcmp)--19044-- REDIR: 0x3283e183f0 (ld-linux-x86-64.so.2:mempcpy) redirected to 0x4a0bd80 (mempcpy)--19044-- Reading syms from /lib64/libc-2.12.so--19044-- REDIR: 0x3284284cd0 (libc.so.6:strcasecmp) redirected to 0x480155c (_vgnU_ifunc_wrapper)--19044-- REDIR: 0x3284286f90 (libc.so.6:strncasecmp) redirected to 0x480155c (_vgnU_ifunc_wrapper)--19044-- REDIR: 0x3284282c40 (libc.so.6:__GI_strrchr) redirected to 0x4a082d0 (__GI_strrchr)--19044-- REDIR: 0x328427a640 (libc.so.6:malloc) redirected to 0x4a07183 (malloc)==19044== Invalid read of size 1==19044==    at 0x4004E4: main (in /home/zhang/document/checker)==19044==  Address 0x4c2b440 is 0 bytes after a block of size 1,024 alloc'd==19044==    at 0x4A0720A: malloc (vg_replace_malloc.c:296)==19044==    by 0x4004D5: main (in /home/zhang/document/checker)==19044== ==19044== Invalid write of size 1==19044==    at 0x4004F4: main (in /home/zhang/document/checker)==19044==  Address 0x4c2b440 is 0 bytes after a block of size 1,024 alloc'd==19044==    at 0x4A0720A: malloc (vg_replace_malloc.c:296)==19044==    by 0x4004D5: main (in /home/zhang/document/checker)==19044== --19044-- REDIR: 0x328427b520 (libc.so.6:free) redirected to 0x4a06b5d (free)==19044== ==19044== HEAP SUMMARY:==19044==     in use at exit: 1,024 bytes in 1 blocks==19044==   total heap usage: 1 allocs, 0 frees, 1,024 bytes allocated==19044== ==19044== Searching for pointers to 1 not-freed blocks==19044== Checked 64,184 bytes==19044== ==19044== 1,024 bytes in 1 blocks are definitely lost in loss record 1 of 1==19044==    at 0x4A0720A: malloc (vg_replace_malloc.c:296)==19044==    by 0x4004D5: main (in /home/zhang/document/checker)==19044== ==19044== LEAK SUMMARY:==19044==    definitely lost: 1,024 bytes in 1 blocks==19044==    indirectly lost: 0 bytes in 0 blocks==19044==      possibly lost: 0 bytes in 0 blocks==19044==    still reachable: 0 bytes in 0 blocks==19044==         suppressed: 0 bytes in 0 blocks==19044== ==19044== ERROR SUMMARY: 3 errors from 3 contexts (suppressed: 4 from 4)==19044== ==19044== 1 errors in context 1 of 3:==19044== Invalid write of size 1==19044==    at 0x4004F4: main (in /home/zhang/document/checker)==19044==  Address 0x4c2b440 is 0 bytes after a block of size 1,024 alloc'd==19044==    at 0x4A0720A: malloc (vg_replace_malloc.c:296)==19044==    by 0x4004D5: main (in /home/zhang/document/checker)==19044== ==19044== ==19044== 1 errors in context 2 of 3:==19044== Invalid read of size 1==19044==    at 0x4004E4: main (in /home/zhang/document/checker)==19044==  Address 0x4c2b440 is 0 bytes after a block of size 1,024 alloc'd==19044==    at 0x4A0720A: malloc (vg_replace_malloc.c:296)==19044==    by 0x4004D5: main (in /home/zhang/document/checker)==19044== --19044-- --19044-- used_suppression:      4 U1004-ARM-_dl_relocate_object /usr/local/lib/valgrind/default.supp:1401==19044== ==19044== ERROR SUMMARY: 3 errors from 3 contexts (suppressed: 4 from 4)

Where the valgrind tool can find it on the http://valgrind.org.