The two functions foo() and bar() are trying to do the same thing. foo
doesn't work but bar does. My question "Is bar a leagal function or is
it treading into the undefined behaviour and I'm simply getting away
with it"? I have tried the code both in VC 6 and VC 2005. Both exhibit
the same behaviour.
As long as I use the ostringstream::str() function as the first output
variable it seems to work. As soon as it appears in a different
location, the code will crash.
#include "stdafx.h"
#include <string>
#include <sstream>
using namespace std;
std::string SomeFunc( const std::string &str )
{
// Iterate through string and calculate a checksum
return " checksum ";
}
void foo()
{
const char stx = '\2';
const char etx = '\3';
std::ostringstream os;
os << stx
<< "One"
<< SomeFunc(os.str().substr(1)) // crashes here
<< etx;
std::string done = os.str();
}
void bar()
{
const char stx = '\2';
const char etx = '\3';
std::ostringstream os;
os << stx
<< "One";
os << SomeFunc(os.str().substr(1)) // works but why?
<< etx;
std::string done = os.str();
}
int main(int argc, char * argv[])
{
argc; argv;
foo(); // doesn't work
bar(); // works fine
return 0;
}