I was toying around with Valgrind, when I noticed something weird: my C++ program does nothing, yet there is 1 memory alloc and 1 free.
My simple program:
int main() { return 0;}when compiled with g++ and checked with Valgrind
> g++ main.cpp> valgrind --leak-check=full --track-origins=yes ./a.out==40790== Memcheck, a memory error detector==40790== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.==40790== Using Valgrind-3.16.0.GIT and LibVEX; rerun with -h for copyright info==40790== Command: ./a.out==40790== ==40790== ==40790== HEAP SUMMARY:==40790== in use at exit: 0 bytes in 0 blocks==40790== total heap usage: 1 allocs, 1 frees, 72,704 bytes allocated==40790== ==40790== All heap blocks were freed -- no leaks are possible==40790== ==40790== For lists of detected and suppressed errors, rerun with: -s==40790== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)My question: My program does nothing. Where does the alloc and free come from?
Interestingly enough, the same program compiled with gcc, shows zero allocs and frees:
> gcc main.c> valgrind --leak-check=full --track-origins=yes ./a.out==40740== Memcheck, a memory error detector==40740== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.==40740== Using Valgrind-3.16.0.GIT and LibVEX; rerun with -h for copyright info==40740== Command: ./a.out==40740== ==40740== ==40740== HEAP SUMMARY:==40740== in use at exit: 0 bytes in 0 blocks==40740== total heap usage: 0 allocs, 0 frees, 0 bytes allocated==40740== ==40740== All heap blocks were freed -- no leaks are possible==40740== ==40740== For lists of detected and suppressed errors, rerun with: -s==40740== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)Follow up question: Why do the two memory allocations differ, for the same piece of code?
compiler: gcc (GCC) 10.1.0
valgrind: valgrind-3.16.0.GIT