Am 12.06.2007, 19:28 Uhr, schrieb Brian Dessent <brian@xxxxxxxxxxx>:
Mihai Don?u wrote:Not that is of great importance, but does anyone know why int main( void ) { return printf( "%d\n", ( int )sizeof( main ) ); } prints 1 ? :) (sizeof( &main ) prints 4/8 as it should)In this context 'main' is a function type, i.e. a type that describes a function of a given return type and a given number and type of arguments (C99 §6.2.5 para. 20). It is invalid to use sizeof() with a function type expression (C99 §6.5.3.4 para. 1) and hence this code invokes undefined behavior. gcc gives a warning if you compile with -pedantic, but otherwise it apparently just returns 1; it would be equally within its rights to return 42 or to generate code to format the users hard drive -- that is the nature of undefined behavior.
If it is invalid to use sizeof() with a function type expression - why not an make it an compile time error?
Martin
