Valgrind
The Valgrind tool suite provides a number of debugging and profiling
tools that help you make your programs faster and more correct. The
most popular of these tools is called Memcheck which can detect
many memory-related errors and memory leaks.
Prepare Your Program¶
Compile your program with -g to include debugging information so that Memcheck's error messages include exact line numbers. Using -O0 is also a good idea, if you can tolerate the slowdown. With -O1 line numbers in error messages can be inaccurate, although generally speaking running Memcheck on code compiled at -O1 works fairly well, and the speed improvement compared to running -O0 is quite significant. Use of -O2 and above is not recommended as Memcheck occasionally reports uninitialised-value errors which don't really exist.
Environmental models for Valgrind in ULHPC¶
$ module purge
$ module load debugger/Valgrind/3.15.0-intel-2019a
Interactive mode¶
Example code:
#include <iostream>
using namespace std;
int main()
{
const int SIZE = 1000;
int *array = new int(SIZE);
for(int i=0; i<SIZE; i++)
array[i] = i+1;
// delete[] array
return 0;
}
# Compilation
$ icc -g example.cc
# Code execution
$ valgrind --leak-check=full --show-leak-kinds=all ./a.out
If we do not delete delete[] array the memory, then there will be a memory leak.
==26756== Memcheck, a memory error detector
==26756== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==26756== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==26756== Command: ./a.out
==26756==
==26756== Invalid write of size 4
==26756== at 0x401275: main (mem-leak.cc:10)
==26756== Address 0x5309c84 is 0 bytes after a block of size 4 alloc'd
==26756== at 0x402DBE9: operator new(unsigned long) (vg_replace_malloc.c:344)
==26756== by 0x401265: main (mem-leak.cc:8)
==26756==
==26756==
==26756== HEAP SUMMARY:
==26756== in use at exit: 4 bytes in 1 blocks
==26756== total heap usage: 2 allocs, 1 frees, 72,708 bytes allocated
==26756==
==26756== 4 bytes in 1 blocks are definitely lost in loss record 1 of 1
==26756== at 0x402DBE9: operator new(unsigned long) (vg_replace_malloc.c:344)
==26756== by 0x401265: main (mem-leak.cc:8)
==26756==
==26756== LEAK SUMMARY:
==26756== definitely lost: 4 bytes in 1 blocks
==26756== indirectly lost: 0 bytes in 0 blocks
==26756== possibly lost: 0 bytes in 0 blocks
==26756== still reachable: 0 bytes in 0 blocks
==26756== suppressed: 0 bytes in 0 blocks
==26756==
==26756== For lists of detected and suppressed errors, rerun with: -s
==26756== ERROR SUMMARY: 1000 errors from 2 contexts (suppressed: 0 from 0)
Result output (without leak)
When we delete delete[] array the allocated memory, there will not be leaked memory.
==26172== Memcheck, a memory error detector
==26172== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==26172== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==26172== Command: ./a.out
==26172==
==26172==
==26172== HEAP SUMMARY:
==26172== in use at exit: 4 bytes in 1 blocks
==26172== total heap usage: 2 allocs, 1 frees, 72,708 bytes allocated
==26172==
==26172== 4 bytes in 1 blocks are definitely lost in loss record 1 of 1
==26172== at 0x402DBE9: operator new(unsigned long) (vg_replace_malloc.c:344)
==26172== by 0x401283: main (in /mnt/irisgpfs/users/ekrishnasamy/BPG/Valgrind/a.out)
==26172==
==26172== LEAK SUMMARY:
==26172== definitely lost: 4 bytes in 1 blocks
==26172== indirectly lost: 0 bytes in 0 blocks
==26172== possibly lost: 0 bytes in 0 blocks
==26172== still reachable: 0 bytes in 0 blocks
==26172== suppressed: 0 bytes in 0 blocks
==26172==
==26172== For lists of detected and suppressed errors, rerun with: -s
==26172== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
Additional information¶
This page is based on the "Valgrind Quick Start Page". For more information about valgrind, please refer to http://valgrind.org/.
Tip
If you find some issues with the instructions above, please report it to us using support ticket.