macro for compile time allocation

[moose]

Can someone explain why the following will not work,

#define MYSTRUCT(name,size) struct my_struct_ ## name {
unsigned char name ## _array[ size ] ;
} ;

MYSTRUCT( foo , 10 )

The error is because the size doesnt appear to be known at compile time
to create the array but why not ? this is a macro not a function.

Any comments welcome

 

[pete]

Can someone explain why the following will not work,

#define MYSTRUCT(name,size) struct my_struct_ ## name {
unsigned char name ## _array[ size ] ;
} ;

You need two backslashes.

#define MYSTRUCT(name,size) struct my_struct_ ## name {\
unsigned char name ## _array[ size ] ;\
} ;

 

[CBFalconer]

Can someone explain why the following will not work,

#define MYSTRUCT(name,size) struct my_struct_ ## name {
unsigned char name ## _array[ size ] ;
} ;

You need two backslashes.

#define MYSTRUCT(name,size) struct my_struct_ ## name {\
unsigned char name ## _array[ size ] ;\
} ;

You might tell him why. #defines have to be complete on one line.
To write them on multiple lines you have to escape the line
endings, which means an escape char (the \) at the end of each
continued line. Nothing follows the escape except the eoln marker.