Читаем Основы программирования в Linux полностью

 /* Неинициализированное чтение */

 ch = ptr[1024];

 /* Запись за пределами блока */

 ptr[1024] = 0;

 /* Потеря блока */

 ptr = 0;

 exit(0);

}

Для применения valgrind вы просто выполняете команду valgrind, передав ей опции, задающие нужные виды проверок, и далее указав программу для выполнения с ее аргументами (если таковые есть).

При выполнении программы с valgrind вы увидите множество обнаруженных проблем:

$ valgrind --leak-check=yes -v ./checker

==4780== Memcheck, a memory error detector.

==4780== Copyright (C) 2002-2007, and GNU GPL'd, by Julian Seward et al.

==4780== Using LibVEX rev 1732, a library for dynamic binary translation.

==4780== Copyright (C) 2004-2007, and GNU GPL'd, by OpenWorks LLP.

==4780== Using valgrind-3.2.3, a dynamic binary instrumentation framework.

==4780== Copyright (C) 2000-2007, and GNU GPL'd, by Julian Seward et al.

==4780==

--4780-- Command line

--4780--    ./checker

--4780-- Startup, with flags:

--4780--    --leak-check=yes

--4780--    -v

--4780-- Contents of /рroc/version:

--4780-- Linux version 2-6.20.2-2-default (geeko@buildhost) (gcc version 4.1.3 20070218 (prerelease) (SUSE Linux)) #1 SMP Fri Mar 9 21:54:10 UTC 2007

--4780-- Arch and hwcaps: X86, x86-sse1-sse2

--4780-- Page sizes: currently 4096, max supported 4096

--4780-- Valgrind library directory: /usr/lib/valgrind

--4780-- Reading syms from /lib/ld-2.5.so (0x4000000)

--4780-- Reading syms from /home/neil/BLP4e/chapter10/checker (0x8048000)

--4780-- Reading syms from /usr/lib/valgrind/x86-linux/memcheck (0x38000000)

--4780--    object doesn't have a symbol table

--4780--    object doesn't have a dynamic symbol table

--4780-- Reading suppressions file: /usr/lib/valgrind/default.supp

--4780-- REDIR: 0x40158B0 (index) redirected to 0x38027EDB (???)

--4780-- Reading syms from /usr/lib/valgrind/x86-linux/vgpreload_core.so (0x401E000)

--4780--    object doesn't have a symbol table

--4780-- Reading syms from /usr/lib/valgrind/x86-linux/vgpreload_memcheck.so (0x4021000)

--4780--    object doesn't have a symbol table

==4780= WARNING: new redirection conflicts with existing -- ignoring it

--4780--    new: 0x040158B0 (index ) R-> 0x04024490 index

--4780-- REDIR: 0x4015A50 (strlen) redirected to 0x4024540 (strlen)

--4780-- Reading syms from /lib/libc-2.5.so (0x4043000)

--4780-- REDIR: 0x40ADFF0 (rindex) redirected to 0x4024370 (rindex)

--4780-- REDIR: 0x40AAF00 (malloc) redirected to 0x4023700 (malloc)

==4780== Invalid read of size 1

==4780==    at 0x804842C: main (checker.с: 10)

==4780== Address 0x4170428 is 0 bytes after a block of size 1,024 alloc'd

==4780==    at 0x4023785: malloc (in /usr/lib/valgrind/x86-linux/vgpreload_memcheck.so)