GNU bug report logs - #6020
coreutils-8.x: a simple feature enhancement, and how to do it

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Message #37 received at 6020 <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: Paul Eggert <eggert <at> CS.UCLA.EDU>
Cc: 6020 <at> debbugs.gnu.org, "Nelson H. F. Beebe" <beebe <at> math.utah.edu>
Subject: Re: bug#6020: coreutils-8.x: a simple feature enhancement,	and how
	to do it
Date: Fri, 30 Apr 2010 23:33:21 +0100

On 30/04/10 19:16, Paul Eggert wrote:
> Pádraig Brady <P <at> draigBrady.com> writes:
> 
>> +#if HAVE_C99_STRTOLD /* provided by c-strtold module.  */
>> +# define STRTOD strtold
>> +#else
>> +# define STRTOD strtod
>> +#endif
>> +
>>    char *ea;
>>    char *eb;
>> -  double a = strtod (sa, &ea);
>> -  double b = strtod (sb, &eb);
>> +  long double a = STRTOD (sa, &ea);
>> +  long double b = STRTOD (sb, &eb);
> 
> This could cause performance problems on machines that have slow
> long-double operations (implemented via traps, say) and that lack
> strtold.

An unusual combination, buy you're right.
I'll push this soon in your name.

thanks for the review,
Pádraig.

commit 1a2afe2adde1f4e864ac098e5d0ede6fcc6b46db
Author: Paul Eggert <eggert <at> cs.ucla.edu>
Date:   Fri Apr 30 23:23:38 2010 +0100

    sort: use long doubles only when effective

    * src/sort.c (general_numcompare): Don't use long double if strtold
    is not available, as it may introduce needless overhead.

diff --git a/src/sort.c b/src/sort.c
index a815244..54b97e2 100644
--- a/src/sort.c
+++ b/src/sort.c
@@ -1856,15 +1856,17 @@ general_numcompare (const char *sa, const char *sb)
      only if A and B can't be compared more cheaply/accurately.  */

 #if HAVE_C99_STRTOLD /* provided by c-strtold module.  */
-# define STRTOD strtold
+# define long_double long double
 #else
-# define STRTOD strtod
+# define long_double double
+# undef strtold
+# define strtold strtod
 #endif

   char *ea;
   char *eb;
-  long double a = STRTOD (sa, &ea);
-  long double b = STRTOD (sb, &eb);
+  long_double a = strtold (sa, &ea);
+  long_double b = strtold (sb, &eb);

   /* Put conversion errors at the start of the collating sequence.  */
   if (sa == ea)

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