Inline Assembly: Difference between revisions

 

One example where this can be useful, is the CMPXCHG instruction (see [http://en.wikipedia.org/wiki/Compare-and-swap Compare and Swap]), which the Linux kernel source code defines as follows:

/* TODO: You should use modern GCC atomic instruction builtins instead of this. */

#include <stdint.h>

__ret; \

}

 

In addition to returning the current value in EAX, CMPXCHG sets the zero flag (Z) when successful. Without asm gotos, your code will have to check the returned value;

this CMP instruction can be avoided as follows:

 

/* TODO: You should use modern GCC atomic instruction builtins instead of this. */

// Works for both 32 and 64 bit

: fail_label ); \

}

 

This new macro could then be used as follows: