[so] Re: valgrind

[Alexandru Mosoi]

cosmin are dreptate, iar pentru exemplificare sa luam programul:


#include <cstdio>
#include <cstdlib>

class A {
public:
~A() {
printf("pe aici nu se trece\n");
}
};

int main() {
A a;
exit(0);
return 0;
}

ai sa vezi, ca acest program comfirma istoria :) (nu e apelat
destructorul lui a). daca comentezi linia cu exit(0) destructorul e
apelat. in prima varianta e o scurgere de memorie... cauzata de faptul
ca exit(0) nu distruge variabilele locale (dar le distruge pe cele
globale/statice). scurgerea asta nu e importanta din moment ce... iesi
din program si memoria oricum e eliberata de SO. ar fi o problema
mare... daca exit() s-ar intoarce :).

On 11/1/07, cosminratiu at gmail.com <cosminratiu at gmail.com> wrote:
> Cred ca situatia este urmatoarea: return 0 da sansa bibliotecii standard C
> sa isi apeleze destructorul de la clasa string. exit(0) iese imediat, fara
> sa apeleze destructorul.
>
> E o non-problema asta pentru tine :).
>
>
> On 11/1/07, Andrei Ciuca <andrei.ciuca at gmail.com> wrote:
> >
> > Salut, ai dreptate.
> > In timp ce scoteam cod, am observat urmatoarea chestie :
> > Daca rulez codul asta :
> >
> > int main()
> > {
> >
> >     cout << "\n> ";
> >     string line;
> >     getline(cin, line);
> >
> >     command_t* root = NULL;
> >     parse_line(line.c_str(), &root);
> >
> >     free_parse_memory();
> >
> >     exit(0);
> >
> > }
> >
> > Da outputul asta :
> >
> > ==2981== Memcheck, a memory error detector.
> > ==2981== Copyright (C) 2002-2006, and GNU GPL'd, by Julian Seward et al.
> > ==2981== Using LibVEX rev 1606, a library for dynamic binary translation.
> > ==2981== Copyright (C) 2004-2006, and GNU GPL'd, by OpenWorks LLP.
> > ==2981== Using valgrind-3.2.0-Debian, a dynamic binary instrumentation
> framework.
> > ==2981== Copyright (C) 2000-2006, and GNU GPL'd, by Julian Seward et al.
> > ==2981== For more details, rerun with: -v
> > ==2981==
> > ==2981== My PID = 2981, parent PID = 2259.  Prog and args are:
> > ==2981==    ./tema1
> > ==2981==
> > --2981-- DWARF2 CFI reader: unhandled CFI instruction 0:50
> > --2981-- DWARF2 CFI reader: unhandled CFI instruction 0:50
> > ==2981==
> > ==2981== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 17 from 1)
> > ==2981== malloc/free: in use at exit: 17 bytes in 1 blocks.
> > ==2981== malloc/free: 12 allocs, 11 frees, 209 bytes allocated.
> > ==2981== For counts of detected errors, rerun with: -v
> > ==2981== searching for pointers to 1 not-freed blocks.
> > ==2981== checked 108,104 bytes.
> > ==2981==
> > ==2981== 17 bytes in 1 blocks are possibly lost in loss record 1 of 1
> > ==2981==    at 0x401B8C7: operator new(unsigned) (vg_replace_malloc.c:163)
> > ==2981==    by 0x40B0C6A:
> std::string::_Rep::_S_create(unsigned, unsigned,
> std::allocator<char> const&) (in /usr/lib/libstdc++.so.6.0.8)
> > ==2981==    by 0x40B1BE9:
> std::string::_Rep::_M_clone(std::allocator<char> const&,
> unsigned) (in /usr/lib/libstdc++.so.6.0.8)
> > ==2981==    by 0x40B35E7: std::string::reserve(unsigned) (in
> /usr/lib/libstdc++.so.6.0.8)
> > ==2981==    by 0x4089126: std::basic_istream<char, std::char_traits<char>
> >& std::getline<char, std::char_traits<char>, std::allocator<char>
> >(std::basic_istream<char, std::char_traits<char> >&,
> std::basic_string<char, std::char_traits<char>, std::allocator<char> >&,
> char) (in /usr/lib/libstdc++.so.6.0.8)
> > ==2981==    by 0x40A2178: std::basic_istream<char, std::char_traits<char>
> >& std::getline<char, std::char_traits<char>, std::allocator<char>
> >(std::basic_istream<char, std::char_traits<char> >&,
> std::basic_string<char, std::char_traits<char>, std::allocator<char> >&) (in
> /usr/lib/libstdc++.so.6.0.8)
> > ==2981==    by 0x80493E9: main (tema1.cpp:875)
> > ==2981==
> > ==2981== LEAK SUMMARY:
> > ==2981==    definitely lost: 0 bytes in 0 blocks.
> > ==2981==      possibly lost: 17 bytes in 1 blocks.
> > ==2981==    still reachable: 0 bytes in 0 blocks.
> > ==2981==         suppressed: 0 bytes in 0 blocks.
> >
> >
> > Daca rulez codul asta (diferenta este ca in loc sa dau "exit(0)" dau
> "return 0" ):
> >
> > int main()
> > {
> >
> >     cout << "\n> ";
> >     string line;
> >     getline(cin, line);
> >
> >     command_t* root = NULL;
> >     parse_line(line.c_str(), &root);
> >
> >     free_parse_memory();
> >
> >     return 0;
> > }
> >
> > atunci valgrind spune ca totul e ok - "no memory leaks possible".
> >
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> >
> >
>
>
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-- 
Alexandru Moşoi
http://alexandru.mosoi.googlepages.com