[patch] fix for the gcc -O3 miscompilation

[patch] fix for the gcc -O3 miscompilation

[Jindrich Makovicka]

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Hi,

the attached patch fixes the long standing breakage when compiling
emacs with newer gcc and -O3 flag. The problem is that -O3 enables
automatic function inlining, which optimizes out the arguments for
the function invocations within eval.c and fns.c, but the functions
expect these values on stack. Adding the "noinline" attribute to these
functions used within eval.c of fns.c seems to solve the problem.

(please Cc:, I am not a subscriber)

Regards,
-- 
Jindrich Makovicka

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Index: eval.c
===================================================================
RCS file: /sources/emacs/emacs/src/eval.c,v
retrieving revision 1.271
diff -u -r1.271 eval.c
--- eval.c	18 Jul 2006 16:33:45 -0000	1.271
+++ eval.c	19 Aug 2006 09:20:10 -0000
@@ -199,6 +202,9 @@
 
 static Lisp_Object funcall_lambda P_ ((Lisp_Object, int, Lisp_Object*));
 static void unwind_to_catch P_ ((struct catchtag *, Lisp_Object)) NO_RETURN;
+
+Lisp_Object apply1 () __attribute__((noinline));
+Lisp_Object call2 () __attribute__((noinline));
 \f
 void
 init_eval_once ()
Index: fns.c
===================================================================
RCS file: /sources/emacs/emacs/src/fns.c,v
retrieving revision 1.413
diff -u -r1.413 fns.c
--- fns.c	26 Jul 2006 18:16:14 -0000	1.413
+++ fns.c	19 Aug 2006 09:20:11 -0000
@@ -387,7 +387,7 @@
   return i1 < SCHARS (s2) ? Qt : Qnil;
 }
 \f
-static Lisp_Object concat ();
+static Lisp_Object concat () __attribute__((noinline));
 
 /* ARGSUSED */
 Lisp_Object

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Re: [patch] fix for the gcc -O3 miscompilation

[Andreas Schwab]

Jindrich Makovicka <makovick@gmail.com> writes:

> the attached patch fixes the long standing breakage when compiling
> emacs with newer gcc and -O3 flag. The problem is that -O3 enables
> automatic function inlining, which optimizes out the arguments for
> the function invocations within eval.c and fns.c, but the functions
> expect these values on stack. Adding the "noinline" attribute to these
> functions used within eval.c of fns.c seems to solve the problem.

IMHO it would be much cleaner to define NO_ARG_ARRAY for all
configurations (effectively removing the option).

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
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