On 11/18/2011 8:32 AM, sachin gupta wrote:
Hi All,
I have a simple program
/*************************/
#include <iostream>
#include <string>
main()
{
std::string test;
test ="abc";
std::string *test2 = new std::string("abc");
delete test2;
}
/******************************************/
Now I am running valgrind over it
valgrind --tool=massif ./a.out
on ms_print
it is howing output as
/****************************************
n time(i) total(B) useful-heap(B) extra-heap(B)
stacks(B)
--------------------------------------------------------------------------------
0 0 0 0
0 0
1 1,385,421 40 28
12 0
2 1,388,597 64 36
28 0
3 1,389,777 104 64
40 0
4 1,393,400 104 64
40 0
61.54% (64B) (heap allocation functions) malloc/new/new[],
--alloc-fns, etc.
->53.85% (56B) 0x3D1709B85F: std::string::_Rep::_S_create(unsigned
long, unsigned long, std::allocator<char> const&) (in
/usr/lib64/libstdc++.so.6.0.8)
| ->26.92% (28B) 0x3D1709D10F: std::string::_M_mutate(unsigned long,
unsigned long, unsigned long) (in /usr/lib64/libstdc++.so.6.0.8)
| | ->26.92% (28B) 0x3D1709D28A: std::string::_M_replace_safe(unsigned
long, unsigned long, char const*, unsigned long) (in
/usr/lib64/libstdc++.so.6.0.8)
| | ->26.92% (28B) 0x4009B2: main (test1.c:6)
| |
| ->26.92% (28B) 0x3D1709C363: ??? (in /usr/lib64/libstdc++.so.6.0.8)
| ->26.92% (28B) 0x3D1709C510: std::basic_string<char,
std::char_traits<char>, std::allocator<char> >::basic_string(char
const*, std::allocator<char> const&) (in /usr/lib64/libstdc++.so.6.0.8)
| ->26.92% (28B) 0x4009E3: main (test1.c:8)
|
->07.69% (8B) 0x4009CD: main (test1.c:8)
/*********************
Why valgrind is showing stack variables in heap. Any idea.
std::string is a std::vector<char>. A vector is dynamically sized (data
can be added or removed ay any time), so it must allocate space from the
heap to store the data inside. There is no special optimization for a
stack variable.
All of this applies to every container object, so practically any
program that uses C++ libraries will allocate space from the heap.
--
David Chapman [email protected]
Chapman Consulting -- San Jose, CA
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