On 12/7/2017 1:36 PM, Yusuf Pisan wrote:
valgrind report memory as being reachable when I think it has been
properly freed in the below program. Is this a bug, a feature, a
misunderstanding of how to use delete by me?
Thanks
Yusuf
===================
#include <iostream>
using namespace std;
int test() {
int* p = new int[5];
delete [] p;
return 0;
}
int main() {
test();
return 0;
}
===================
$ uname -a
Linux uw1-320-10 4.4.0-98-generic #121-Ubuntu SMP Tue Oct 10 14:24:03
UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
$ valgrind --version
valgrind-3.11.0
$ g++ --version
g++ (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609
$ g++ -g -Wall -Wextra valgrind-example.cpp -o valgrind-example
$ valgrind --leak-check=full --show-leak-kinds=all ./valgrind-example
==11597== Memcheck, a memory error detector
==11597== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==11597== Using Valgrind-3.11.0 and LibVEX; rerun with -h for
copyright info
==11597== Command: ./valgrind-example
==11597==
==11597==
==11597== HEAP SUMMARY:
==11597== in use at exit: 72,704 bytes in 1 blocks
==11597== total heap usage: 2 allocs, 1 frees, 72,724 bytes allocated
==11597==
==11597== 72,704 bytes in 1 blocks are still reachable in loss record
1 of 1
==11597==at 0x4C2DB8F: malloc (in
/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==11597==by 0x4EC3EFF: ??? (in
/usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.21)
==11597==by 0x40106B9: call_init.part.0 (dl-init.c:72)
==11597==by 0x40107CA: call_init (dl-init.c:30)
==11597==by 0x40107CA: _dl_init (dl-init.c:120)
==11597==by 0x4000C69: ??? (in /lib/x86_64-linux-gnu/ld-2.23.so
<http://ld-2.23.so>)
==11597==
==11597== LEAK SUMMARY:
==11597==definitely lost: 0 bytes in 0 blocks
==11597==indirectly lost: 0 bytes in 0 blocks
==11597==possibly lost: 0 bytes in 0 blocks
==11597==still reachable: 72,704 bytes in 1 blocks
==11597== suppressed: 0 bytes in 0 blocks
==11597==
==11597== For counts of detected and suppressed errors, rerun with: -v
==11597== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
$
Look at the call chain - the still-reachable memory is allocated outside
of your code. It looks like the fault is in the C++ startup library
that is provided by your Linux installation. You could add a valgrind
suppression to hide this "false positive" (as far as your program is
concerned) but I've never bothered; I simply learn to ignore them.
--
David Chapman dcchap...@acm.org
Chapman Consulting -- San Jose, CA
EDA Software Developer, Expert Witness
www.chapman-consulting-sj.com
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