2 ms·

I started but couldn't finish. For example FILE (and LINE and similar) certainly can be used in user-written macros, but they evaluate to the file/line

I started but couldn't finish. For example __FILE__ (and __LINE__ and similar) certainly can be used in user-written macros, but they evaluate to the file/line they appear at in the macro source, not at the line the macro is invoked.

elteto 4y ago
This is not correct. They evaluate at the point where they are expanded. I’ve used them countless of times to implement “log” and “trace” macros that show file/line.
- zabzonk 4y ago
  I have used them countless timers myself, but not within another macro Edit: Sorry I am on multiple drugs at the moment for a severe fracture - I'm a bit confused, nurse has just been. I will shut up now. To prove I am not completely out of it (though wrong), here's one I wrote a lot earlier: https://latedev.wordpress.com/2012/08/09/c-debug-macros/ https://latedev.wordpress.com/2012/08/09/c-debug-macros/
  - elteto 4y ago
    Sorry to hear that! Rest up and don’t worry about cpp macros for now ;) they’ll still be there after you heal. Good luck!
    - seoaeu 4y ago
      Honestly, I suspect that cpp macros will outlive us all
- gpderetta 4y ago
  most commonly they are typically used in the definition of the assert macro. For example: https://github.com/lattera/glibc/blob/master/assert/assert.h https://github.com/lattera/glibc/blob/master/assert/assert.h .
camel-cdr 4y ago
> they evaluate to the file/line they appear at in the macro source, not at the line the macro is invoked. What are you talking about? Maybe I'm missing your point, but: #define A __LINE__ A A Expands to: 2 3