Re: Is overriding a function of a library in accordance with C++ standard?

From:

"Tom Widmer [VC++ MVP]" <tom_usenet@hotmail.com>

Newsgroups:

microsoft.public.vc.language

Date:

Fri, 25 Aug 2006 10:41:26 +0100

Message-ID:

<ei1jkqCyGHA.4336@TK2MSFTNGP06.phx.gbl>

Lighter wrote:

Is overriding a function of a library in accordance with C++ standard?

The following code is passed by the VS 2005 and Dev C++.

#include <cstdlib>

What about:
#include <cstring>
or
#include <string.h>

#include <iostream>

using namespace std;

size_t strlen(const char* p)
{
    return 0;
} // !!! Note this !!! The standard library function strlen is deliberately overriden.

int main(int argc, char *argv[])
{

    system("PAUSE");

    return EXIT_SUCCESS;
}

There is even no warning after compiling the code. In front of the
fact, I have to make a guess that all the C++ compilers are conformed
to the following rules:

1) The compiler first compiles all the source file included in the
project into object files;

2) At link time, the compiler first searches the object files for all
the unresolved symbols; if it fails to find some symbols, then the
compiler will search the libraries which are included in the project to
find the symbols.

3) If the object files containes a symbol, then the symbols that have
the same name in the libraries will be ignored.

Am I correct?

For many compilers, strlen is a compiler intrinsic, and therefore built
into the compiler rather than a library. What you are doing is undefined
behaviour.

Tom