[Dev-C++] const modifier?

[Abhijit S. <mu...@gm...>]

I was just going through the sources of the class libraries in Turbo C++
version 3.0, and found this code. How does the program modify aPtr even
though it says it's a const?

-------CLASSLIB/SOURCE/STRNG.CPP------
String::String( const char *aPtr )
{
    if ( aPtr == 0 )
        aPtr = "";

    len = strlen( aPtr ) + 1;
    theString = new char[ len ];
    CHECK( theString != 0 );
    strcpy( theString, aPtr );
}
--------------------------------------

After seeing this, I tried compiling the following file in MingW, and it did
(with -Wall, no warnings)

--------------------------------------
void  do_stuff(const char *buf)
{
  if(!buf)
    buf = "";
}

int main()
{
  do_stuff(0);
  return 0;
}
--------------------------------------

How? Doesn't
    buf = "";
translate to assign "" to buf?

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