jscherman jscherman - 2 months ago 26
C++ Question

Cannot find memory leak detected by Valgrind

I'm running and analyzing with Valgrind this

int main() {
Set<int> c;
return 0;
}


So the output is:

jscherman@jscherman:~/ClionProjects/algo2-t3-bts$ g++ set.hpp tests.cpp && valgrind --leak-check=yes --show-leak-kinds=all ./a.out
==3528== Memcheck, a memory error detector
==3528== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==3528== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==3528== Command: ./a.out
==3528==
test_mleak...ok
==3528==
==3528== HEAP SUMMARY:
==3528== in use at exit: 72,704 bytes in 1 blocks
==3528== total heap usage: 2 allocs, 1 frees, 73,728 bytes allocated
==3528==
==3528== 72,704 bytes in 1 blocks are still reachable in loss record 1 of 1
==3528== at 0x4C2DC10: malloc (vg_replace_malloc.c:299)
==3528== by 0x4EC3EFF: ??? (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.21)
==3528== by 0x40104E9: call_init.part.0 (dl-init.c:72)
==3528== by 0x40105FA: call_init (dl-init.c:30)
==3528== by 0x40105FA: _dl_init (dl-init.c:120)
==3528== by 0x4000CF9: ??? (in /lib/x86_64-linux-gnu/ld-2.23.so)
==3528==
==3528== LEAK SUMMARY:
==3528== definitely lost: 0 bytes in 0 blocks
==3528== indirectly lost: 0 bytes in 0 blocks
==3528== possibly lost: 0 bytes in 0 blocks
==3528== still reachable: 72,704 bytes in 1 blocks
==3528== suppressed: 0 bytes in 0 blocks
==3528==
==3528== For counts of detected and suppressed errors, rerun with: -v
==3528== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)


Apparently, i'm loosing memory at the constructor of Set, but i can't find the actual reason. This is how i implemented Set (in a BTS):

template<class T>
class Set {
public:
Set() : root_(NULL), cardinal_(0) {}
~Set() {delete root_;}
void insert(const T &);
bool belongs(const T &) const;
void remove(const T &);
const T &min() const;
const T &max() const;
unsigned int cardinal() const;

private:

struct Node {
Node(const T &v) : value(v), left(NULL), right(NULL) {}
~Node() {delete right; delete left;}
T value;
Node *left;
Node *right;
};

Node *root_;
int cardinal_;
}


Any idea how to solve this leak? Thanks!

Answer

You're not leaking anything--you're just misunderstanding what valgrind is telling you.

It thinks there may be some problem underneath _dl_init(), but this is a red herring. You can safely add it to your valgrind suppressions file (which is always a good thing to have, so you aren't bothered by false alarms from system libraries).