Bug 115453

Summary: strtof is broken
Product: Red Hat Enterprise Linux 2.1 Reporter: Ragnar Hojland Espinosa <ragnar>
Component: glibcAssignee: Jakub Jelinek <jakub>
Status: CLOSED NOTABUG QA Contact: Brian Brock <bbrock>
Severity: high Docs Contact:
Priority: high    
Version: 2.1CC: fweimer
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Target Release: ---   
Hardware: i686   
OS: Linux   
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Fixed In Version: Doc Type: Bug Fix
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Last Closed: 2004-02-13 12:27:21 UTC Type: ---
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Description Ragnar Hojland Espinosa 2004-02-12 17:18:54 UTC 
From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.6) Gecko/20040120

Description of problem:
#include <stdlib.h>
main()
{
   printf ("%f\n", strtof ("+5.7344E+02", 0));
   return 0;
}

erroneously prints:
0.000000

and worse,

#include <stdlib.h>
main()
{
   char foo;
   printf ("%f\n", strtof ("+5.7344E+02", 0));
   return 0;
}

prints:
245504.625029


Version-Release number of selected component (if applicable):
glibc-2.2.4-26

How reproducible:
Always

Steps to Reproduce:
compile above

Additional info:

No rpms have been updated; this bug is also present in more modern glibcs.
Comment 1 Jakub Jelinek 2004-02-13 12:27:21 UTC 
If you used -Wall option, GCC would tell you what's wrong:
/tmp/x.c:3: warning: return type defaults to `int'
/tmp/x.c: In function `main':
/tmp/x.c:4: warning: implicit declaration of function `printf'
/tmp/x.c:4: warning: implicit declaration of function `strtof'
/tmp/x.c:4: warning: double format, different type arg (arg 2)

The problem is that strtof, being ISO C99+ function, is not prototyped
in ISO C90 compilations, as that would violate namespace rules.
See info libc on Feature Set Macros.
Compiling with -std=c99, -std=gnu99, -D_GNU_SOURCE or -D_ISOC99_SOURCE
(and also #include <stdio.h> for printf while you're at it) will fix it up.