Re: AC_TRY_COMPILE() annoyances with 2.63b

[Mike Frysinger]

On Sunday 05 April 2009 21:01:29 Mike Frysinger wrote:
> On Sunday 05 April 2009 20:46:03 Eric Blake wrote:
> > That said, autoconf could probably be taught that, for some macros, an
> > argument of all whitespace is morally equivalent to an empty argument.
> > Patches welcome.
>
> i'm not an expert by any means with internal autoconf/m4.  if there's a m4
> helper function to test whether an argument contains something other than
> whitespace, then the change to m4sh.m4:_AS_IF is trivial ... use that
> rather than m4_ifvaln([$1],....

to answer my own question and to post a patch, m4_normalize can be used:

diff --git a/lib/m4sugar/m4sh.m4 b/lib/m4sugar/m4sh.m4
index 88881b1..605918b 100644
--- a/lib/m4sugar/m4sh.m4
+++ b/lib/m4sugar/m4sh.m4
@@ -606,7 +606,7 @@ m4_define([_AS_IF],
   m4_default([$2], [:])
 ])
 m4_define([_AS_IF_ELSE],
-[m4_ifvaln([$1],
+[m4_ifvaln(m4_normalize([$1]),
 [else
   $1])])
 

this should "fix" every macro that uses AS_IF with an "else" argument.  it 
certainly fixes my test case.
-mike

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