"\n\t" in inline asm

"\n\t" in inline asm

[Martynas Kunigelis]

Good day,

I use inline assembly quite often and I am a little disturbed by the
need to append "\n\t" to the end of every inline assembly line. This
makes the code much less readable, so I end up using a preprocessor hack
like this:

#define _ "\n\t"

asm (
  "movl %0,%1"  _
  "decl %2"     _
  "int $0x80"
  : /* this is just an example */
  : "=r" (0) /* whatever */
);

#undef _

While experimenting I tried using commas at the end of each line, like
this:

asm (
  "movl %0,%1",
  "decl %2",     
  "int $0x80"
  : /* this is just an example */
  : "=r" (0) /* whatever */
);

It compiled w/o problems, but the resulting .s file had only the last
line from the inline asm statement, that is "int $0x80". It seems as if
it was evaluated as a regular C statement, like  "a = 1, 2, 3, 4;" would
result in a == 4.

I would like to make a suggestion to add somewhat more special handling
of inline asm() statements, and make a comma appent the "cursed" "\n\t"
to each line. That wouldn't break any existing code and it would allow
one to "beautify" the inline assembly code a lot more.

-Martynas

Re: "\n\t" in inline asm

[Andreas Schwab]

Martynas Kunigelis <mkunigelis@alna.lt> writes:

|> I use inline assembly quite often and I am a little disturbed by the
|> need to append "\n\t" to the end of every inline assembly line.

You can use a semicolon instead.  But this depends on the assembler, the
compiler does not interpret anything inside the string except % escapes.

-- 
Andreas Schwab                                      "And now for something
schwab@issan.cs.uni-dortmund.de                      completely different"
schwab@gnu.org

Re: "\n\t" in inline asm

[Philip Blundell]

>I use inline assembly quite often and I am a little disturbed by the
>need to append "\n\t" to the end of every inline assembly line. This

You don't.  You can write it like this:

asm (
  "movl %0,%1
   decl %2
   int $0x80"
  : /* this is just an example */
  : "=r" (0) /* whatever */
);

p.

Re: "\n\t" in inline asm

[Gilles-Claude Rajaobelina]

Martynas Kunigelis wrote:

> While experimenting I tried using commas at the end of each line, like
> this:
>
> asm (
>   "movl %0,%1",
>   "decl %2",
>   "int $0x80"
>   : /* this is just an example */
>   : "=r" (0) /* whatever */
> );
>
>

This is how I would have written it:
asm ("
  movl %0,%1;
  decl %2;
  int $0x80;"
  : /* this is just an example */
  : "=r" (0) /* whatever */
);

--
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Re: "\n\t" in inline asm

[Jamie Lokier]

On Thu, Dec 10, 1998 at 12:08:48PM +0100, Philip Blundell wrote:
> >I use inline assembly quite often and I am a little disturbed by the
> >need to append "\n\t" to the end of every inline assembly line. This
> 
> You don't.  You can write it like this:
> 
> asm (
>   "movl %0,%1
>    decl %2
>    int $0x80"
>   : /* this is just an example */
>   : "=r" (0) /* whatever */
> );


But then the assembly output is ugly.  The point of using "\n\t" is that
it matches up with GCC's generated code in the output file.

I like the suggestion for parsing commas between strings as line
separators.  Semicolons instead of commas might be easier (they work for
`for'), but they're a bit uglier IMO and easily confused with colons.

-- Jamie