When is the std::string dstor called in the following code

[mathieu]

Hi C++ gurus,

Why in the following code the std::string destructor is being called
before the 'catch' ?

Thanks,
-Mathieu

#include <iostream>
#include <sstream>

void foo()
{
std::ostringstream os;
os << "my error";
throw os.str().c_str();
}

int main()
{
try
{
foo();
}
catch(const char *msg)
{
std::cerr << msg << std::endl;
}
return 0;
}

[Martin York]

On Feb 12, 12:09 am, mathieu <[e-mail]:

Hi C++ gurus,

Why in the following code the std::string destructor is being called

void foo()
{
.....
throw os.str().c_str();

os.str() creates a std::string object and returns it as a result. As
you are using it in an expression it is a temporary object and thus
will be destroyed at the end of the statement.

The value returned by c_str() is not valid beyond the lifetime of the
object it was called on. So your best bet to actually throw the
std::string object.

int main()
{
try
{
foo();
}

Add
catch(std::string const& e)
{
std::cerr << e << std::endl;
}

catch(const char *msg)
{
std::cerr << msg << std::endl;
}
return 0;

}