And you are correct about VC++ doing the right thing with sizeof as opposed to strlen().
Didn't use to be like that years ago. I've been burned too many times by doing a sizeof on a constant character string which always returned a size of the pointer that I never do it anymore.
Are you sure you were using
sizeof(...) correctly? sizeof(...) is a compile-time operator and as such can only determine the size of variables that are known at that point in compilation. For example:
char caArray[ 32 ];
strcpy( caArray, "Hi!" );
TRACE( "sizeof: %d/n", sizeof( caArray ) ); // Returns "32"
TRACE( "strlen: %d/n", strlen( caArray ) ); // Returns "3"
In the above code,
sizeof(...) works correctly because caArray is of a size known at the point where sizeof(...) is encountered; it is created and referenced in the same (or nested) scope. However, if you pass caArray to a function (creating a brand new scope), it degrades to a normal pointer, and sizeof(...) will return the size of a pointer, because at compile-time, it has no idea what will be passed for that parameter. For example:
int GetSize( char caArray[] ) { return( sizeof( caArray ) ); };
//
// ...
//
char caArray[ 32 ];
strcpy( caArray, "Hi!" );
TRACE( "sizeof: %d/n", sizeof( caArray ) ); // Returns "32"
TRACE( "strlen: %d/n", strlen( caArray ) ); // Returns "3"
TRACE( "GetSize: %d/n", GetSize( caArray ) ); // Returns "4"
Note that even though I put
char caArray[] as the parameter to the function, it still becomes a pointer-to-char. Also, if you compile this code on Warning Level 4, you will get a warning about caArray being an "unreferenced parameter". Why? Because sizeof(...) is a compile-time operator, so it resolves to a constant value of 4, technically leaving caArray out of the picture.The reason
sizeof("ms-help://") works is because is size is known (note that it includes the terminating NUL character). But as with the stack-allocated array above, once you pass it to a function, it degrades from a "constant array" into a plain old pointer.Peace!
-=- James
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