This column is motivated by an email that was recently sent to us. 
A C++ programmer who had recently received the latest version of 
his C++ compiler was puzzled because he was no longer able to use 
pointers to extern "C" functions and pointers to C++ functions 
interchangeably. Was this a bug in the new compiler or was this a 
new feature of Standard C++? And if this was a new feature of Standard 
C++, how could he work around it? The short answer to the first 
question is that yes, in Standard C++, pointers to C functions and 
pointers to C++ functions can no longer be used interchangeably. In 
this column, we examine the consequences of this new language rule 
more closely.