unify usage of inline assembly keywords

[kaspar030]

From "https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html":

"The asm keyword is a GNU extension. When writing code that can be compiled with -ansi and the various -std options, use __asm__ instead of asm (see Alternate Keywords). "

Stumbled upon this when trying to compile with -std=c11, which doesn't allow asm().

[Kijewski]

In this case I'd rather #define asm __asm__.

[kaspar030]

Why, if gcc suggests usage of __asm__?

[Kijewski]

Because it's ugly. Other than that I have no particular reason to prefer a #define over a %s/…/…/g.

[kaspar030]

I don't find it ugly, but I also don't care. What would be the prefered location of such a define?

[OlegHahm]

I find it confusing to define a macro with the same name as a GCC extension.

[Kijewski]

What would be the prefered location of such a define?

Actually, I have no idea. Please ignore my remarks. :)

[jnohlgard]

__asm__ is still a GCC extension.

This is how CMSIS solves the described issue for different compilers: https://github.com/RIOT-OS/RIOT/blob/master/cpu/cortexm_common/include/core_cm0.h#L79

[haukepetersen]

I would tend to go with __asm__, before having an asm define somewhere.

asm is still a GCC extension

but if it solves the issue for c11, I think we should prefer it over asm()?! I don't have a strong opinion here, but if we want to switch to __asm__, I would definitely prefer to use it directly over some mapping macro.

[jnohlgard]

👍 for unifying, I don't have a strong opinion on what the outcome is as long as it is unified across the tree.
I guess a well-written regex could fix it for all occurrences.

[kaspar030]

This PR should unify as is. Only file I didn't touch is cpu/x86/nop_nop_nop.inc, which I'm not sure is needed at all.

[jnohlgard]

Btw, from quickly looking at the diff I believe that there may be some missing volatile keywords at some of the inline asm.

[kaspar030]

@gebart you mean like here?

[jnohlgard]

Yes, like there
On Mar 31, 2016 10:33 PM, "Kaspar Schleiser" notifications@github.com
wrote:

In boards/telosb/board.c
#5059 (comment):

@@ -67,7 +67,7 @@ void msp430_init_dco(void)
BCSCTL1 |= DIVA1 + DIVA0; /* ACLK = LFXT1CLK/8 */

 for (i = 0xFFFF; i > 0; i--) {        /* Delay for XTAL to settle */

•    asm("nop");
  

•    **asm**("nop");
  

@gebart https://github.com/gebart you mean like here?

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https://github.com/RIOT-OS/RIOT/pull/5059/files/c3f7186d4e686561b3e5714d91819d1b361542cd#r58122804

[kaspar030]

Will open an issue. edit #5218

[kaspar030]

(launching CI to check for build errors)

[jnohlgard]

ACK