typed cast's

[Frank Klemm <pfk at fuchs dot offl dot uni-jena dot de>]

This has nothing to do with optimization.

This has something to do with the parser.



In C you can convert an expression of (nearly) any type to another type.

    float  f = (float) (&f);

Typecasting is dangerous. But sometimes you need typecasting.
Often you want to cast type A to type B.
C has only the possibity to cast any type to type B.


int    x [128];
float  f [128];

// p is a char*, but can also work with int-data from x, but never can work with float data)
char*  p = (char*) x;		// dangerous
char*  p = (char*) f;		// bug, but C can't determine that

char*  q = (char*,int*) x;	// explicit convering from int* to char*	
char*  q = (char*,int*) f;	// compile time error

Especially if you are using macros this can be useful to determine bugs as
early as possible.


Syntax:

	(dest_type)
	(dest_type,allowed_src_type)
	(dest_type,allowed_src_type1,allowed_src_type2)
	(dest_type,allowed_src_type1,allowed_src_type2,allowed_src_type3)

etc.

Examples:
	(size_t,int)-1
	(void*,int)0
	*p++   = (uint8_t,uint32_t)(word32 >>  8);
	*p++ = (int,unsigned int) Bitstream_read (Res_bit[Res[Band].R]) - Dc[Res[Band].R];


-- 
Frank Klemm