Tuesday, July 17, 2007

const overload functions taking char pointers

Always have two overloaded versions of functions that take
char * and const char * parameters. Declare (but don't define if not needed)
a function that takes const char* as a parameter when you have defined
a function that accepts a non-const char* as a parameter.

#include <iostream>
#include <iomanip>

static void foo (char *s) {
std::cout << "non-const " << std::hex << static_cast <void *>(s) << std::endl;
}
static void foo (char const *s) {
std::cout << "const " << std::hex << static_cast <void const *>(s) << std::endl;
}

int main (void)
{
char * c1 = "Literal String 1";
char const * c2 = "Literal String 1";
foo (c1);
foo (c2);
foo ("Literal String 1");
//*c1 = 'l'; // This will cause a seg-fault on Linux.
std::cout << c2 << std::endl;

return 0;
}

Because of default conversion rule from string literal to char *,
the call to foo using in-place literal goes completely undetected
through the eyes of compiler's type system.

Interestingly enough, the addresses of all the identical string literals
is the same, irrespective of whether it is assigned to const or non-const.
Internally though, they are stored on the const DATA page and modifying
them causes a seg-fault.

Friday, July 06, 2007

Future of C++ track @ ACCU

Recently held ACCU 2007 conference had a track dedicated to C++ called: Future of C++ Track. I have listed the presentations in that track and some other related presentations for a quick reference.

* An Outline of C++0x (Bjarne Stroustrup)
* Generalizing Constant Expressions in C++ (Jens Maurer)
* C++0x Initilaisation: Lists and a Uniform Syntax (Bjarne Stroustrup)
* An Introduction to the Rvalue Reference in C++0x (Howard Hinnant)
* C++ has no useful purpose (Russel Winder)
* C++ Modules (David Vandevoorde)
* Support for Numerical Programming in C++ (Walter Brown)
* C++ Threads (Lawrence Crowl)
* Standard Library report (Alisdair Meredith)
* Concepts: An Introduction to Concepts in C++0x (Doug Gregor) (OOPSLA06 paper)