Re: unoptimized autoconf generated code

[Eric Blake]

According to Ralf Wildenhues on 3/2/2010 2:45 PM:
> Hi Eric,
> 
> * Eric Blake wrote on Tue, Mar 02, 2010 at 07:04:52AM CET:
>> Here's an updated version of patch 2/3 of the previous post; I realized
>> that ${a+b} should not be treated as a simple indirection, and added some
>> documentation.  Patch 1/3 and 3/3 are unchanged.
> 
> This patch causes a number of testsuite regressions.  The AS_BOX patch
> has a typo s/@var/@ovar/ in the manual causing a texinfo warning.

Thanks for a review.  Certainly still a work in progress, and I won't
commit without a complete successful testsuite run.

> 
> While working on AS_LITERAL_IF, you might want to fix the typo near the
> beginning of the description:
>   # If EXPRESSION has shell indirections ($var or `expr`), expand
>   # IF-LITERAL, else IF-NOT-LITERAL.
> 
> That should be "has no shell indirections".

Yep.

> 
> If you're really motivated, then you could also look into this code
> snippet taken from the manual:
> 
>   header="sys/some file.h"
>   AS_TR_SH([HAVE_$header])=yes
>   if test "x$HAVE_sys_some_file_h" = xyes; then echo "Have it!"; fi
> 
> which has been broken presumably by one of the earlier AS_LITERAL_IF
> changes already.  (This is not a recent regression, so feel free to
> ignore right now.)

Actually, it's a doc bug.  This is not valid shell variable assignment:

`echo $foo`=yes

So this patch is going in now, while I spend more time fixing the actual
code changes.

-- 
Don't work too hard, make some time for fun as well!

Eric Blake             e...@byu.net

From d174a5362e1adc52d9ef0e9448b2ad142512e42f Mon Sep 17 00:00:00 2001
From: Eric Blake <ebl...@redhat.com>
Date: Tue, 2 Mar 2010 15:39:58 -0700
Subject: [PATCH] Fix shell code in AS_TR_SH documentation.

* doc/autoconf.texi (Common Shell Constructs) <AS_TR_SH>: Fix
example to expand to valid shell code.
Reported by Ralf Wildenhues.

Signed-off-by: Eric Blake <ebl...@redhat.com>
---
 ChangeLog         |    5 +++++
 doc/autoconf.texi |    7 +++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 747a629..5aae86c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2010-03-02  Eric Blake  <ebl...@redhat.com>

+       Fix shell code in AS_TR_SH documentation.
+       * doc/autoconf.texi (Common Shell Constructs) <AS_TR_SH>: Fix
+       example to expand to valid shell code.
+       Reported by Ralf Wildenhues.
+
        Improve documentation on AC_{COMPILE,LINK}_IFELSE.
        * doc/autoconf.texi (Running the Compiler): Mention that the
        object file is available after a successful compile.
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 7838f76..8fca9ae 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -13206,12 +13206,15 @@ Common Shell Constructs

 @defmac AS_TR_SH (@var{expression})
 @asindex{TR_SH}
-Transform @var{expression} into a valid shell variable name.  For example:
+Transform @var{expression} into shell code that generates a valid shell
+variable name.  The result is literal when possible at m4 time, but must
+be used with @code{eval} if @var{expression} causes shell indirections.
+For example:

 @example
 # This outputs "Have it!".
 header="sys/some file.h"
-AS_TR_SH([HAVE_$header])=yes
+eval AS_TR_SH([HAVE_$header])=yes
 if test "x$HAVE_sys_some_file_h" = xyes; then echo "Have it!"; fi
 @end example
 @end defmac
-- 
1.6.6.1

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