[Bug libc/4342] New: scanf %lg problem with hex numbers

[Bug libc/4342] New: scanf %lg problem with hex numbers

[madcoder at debian dot org]

scanf makes exponents specifiers mandatory whereas it should not. The code to 
reproduce the problem is:



#include <stdio.h>

int
main (void)
{
    double d = -999;
    int  ret;

    ret =  sscanf ("0x100", "%lg", &d);
    printf ("%d %g\n", ret, d);

    ret =  sscanf ("0x100p0", "%lg", &d);
    printf ("%d %g\n", ret, d);

    return 0;
}


expected output would be:
1 256
1 256

it gives currently:
0 -999
1 256

-- 
           Summary: scanf %lg problem with hex numbers
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: madcoder at debian dot org
                CC: glibc-bugs at sources dot redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=4342

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[Bug libc/4342] scanf %lg problem with hex numbers

[jakub at redhat dot com]

------- Additional Comments From jakub at redhat dot com  2007-04-23 13:44 -------
That's how *scanf initially worked, till the
1999-08-13  Ulrich Drepper  <drepper@cygnus.com>

        * stdio-common/tstscanf.c: Add test for hexadecimal float parsing
        problem.

        * stdio-common/vfscanf.c: Don't recognize hexadecimal floats without
        exponent.

--- stdio-common/vfscanf.c      21 Jun 1999 13:35:40 -0000      1.67
+++ stdio-common/vfscanf.c      13 Aug 1999 19:41:26 -0000      1.68
@@ -1410,8 +1410,8 @@ __vfscanf (FILE *s, const char *format, 

          /* Have we read any character?  If we try to read a number
             in hexadecimal notation and we have read only the `0x'
-            prefix this is an error.  */
-         if (wpsize == 0 || (is_hexa && wpsize == 2))
+            prefix or no exponent this is an error.  */
+         if (wpsize == 0 || (is_hexa && (wpsize == 2 || ! got_e)))
            conv_error ();

        scan_float:
--- stdio-common/tstscanf.c     6 Jun 1999 09:18:57 -0000       1.12
+++ stdio-common/tstscanf.c     13 Aug 1999 22:39:01 -0000      1.13
@@ -250,5 +250,20 @@ main (int argc, char **argv)
       }
   }
 
+  fputs ("Test 8:\n", stdout);
+  {
+    double d = 123456.789;
+    int res;
+
+    res = sscanf ("0x1234", "%lf", &d);
+    printf ("res = %d, d = %f\n", res, d);
+
+    if (res != 0 || d != 123456.789)
+      {
+       fputs ("test failed!\n", stdout);
+       result = 1;
+      }
+  }
+
   exit (result);
 }  

change.  My reading of both ISO C99 and current POSIX suggests that indeed
the exponent is only optional.  While ISO C99 has a footnote:
"fscanf pushes back at most one input character onto the input stream.
Therefore, some sequences that are acceptable to strtod, strtol, etc., are
unacceptable to fscanf." I don't think this applies here, as the hexadecimal
float exponent part is structured the same as decimal exponent part, just with
a different letter (p vs. e) and as the decimal float has the exponent part
optional, there is no reason why it couldn't be optional even for hexadecimal
floats.


-- 


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[Bug libc/4342] scanf %lg problem with hex numbers

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2007-04-27 20:29 -------
I changed the code in cvs.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


http://sourceware.org/bugzilla/show_bug.cgi?id=4342

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[Bug libc/4342] scanf %lg problem with hex numbers

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2007-07-12 15:14 -------
Subject: Bug 4342

CVSROOT:	/cvs/glibc
Module name:	libc
Branch: 	glibc-2_5-branch
Changes by:	jakub@sourceware.org	2007-07-12 15:13:48

Modified files:
	.              : ChangeLog 
	stdio-common   : tstscanf.c vfscanf.c 

Log message:
	2007-04-27  Ulrich Drepper  <drepper@redhat.com>
	
	[BZ #4342]
	* stdio-common/vfscanf.c (_IO_vfscanf_internal): Allow
	hexa-decimal floats without exponent.
	* stdio-common/tstscanf.c (main): Adjust Test 8 test for success.

Patches:
http://sourceware.org/cgi-bin/cvsweb.cgi/libc/ChangeLog.diff?cvsroot=glibc&only_with_tag=glibc-2_5-branch&r1=1.10362.2.75&r2=1.10362.2.76
http://sourceware.org/cgi-bin/cvsweb.cgi/libc/stdio-common/tstscanf.c.diff?cvsroot=glibc&only_with_tag=glibc-2_5-branch&r1=1.21&r2=1.21.10.1
http://sourceware.org/cgi-bin/cvsweb.cgi/libc/stdio-common/vfscanf.c.diff?cvsroot=glibc&only_with_tag=glibc-2_5-branch&r1=1.115&r2=1.115.2.1



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