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Re: code for 32/64 bit strtoul strtol strtoull strtoll

From Keith Thompson <kst-u@mib.org>
Newsgroups comp.lang.c
Subject Re: code for 32/64 bit strtoul strtol strtoull strtoll
Date 2015-03-29 12:15 -0700
Organization None to speak of
Message-ID <87mw2vlinn.fsf@kst-u.example.com> (permalink)
References <mf9605$7oq$1@speranza.aioe.org> <lj9gha5v5adefueiavvtbk5ap4207khp8b@4ax.com> <mf9bcd$nr5$1@speranza.aioe.org>

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jacob navia <jacob@jacob.remcomp.fr> writes:
> Le 29/03/2015 18:44, Barry Schwarz a écrit :
>> The if evaluates to true and 0 is correct return value but *endptr
>> still points to '0' when it should point to 'x'.  Since 0x is not a
>> valid hex constant, the string "0x" should be treated the same as
>> "0a".
>>
>
> That would be the case if the standard was logical but it is
> explicitely stated that 0x should NOT advance the pointer.
>
> <quote>
> C99:
> 7 If the subject sequence is empty or does not have the expected form,
> no conversion is performed; the value of nptr is stored in the object
> pointed to by endptr, provided that endptr is not a null pointer.
> <end quote>
>
> In this case the sequence has not the expected form, i.e. an
> hexadecimal number

"0x" does not have the expected form.  "0" does.

strtol("0x", endptr, 0) should return 0 and set *endptr to point to the
'x'.  The expected form is not a hexadecimal number; it's a number (with
optional sign) that may or may not have a leading 0x.

You use the identifier _Strtoull, which is reserved.  That's ok for code
that's part of the implementation, which this is intended to be.  But
since the function is static, it's not necessary to use a reserved
identifier.

In your main program (enabled if TEST is #defined), you assign the
result of strtoll() to an unsigned long long object.  When I run your
program with an argument of "-1", I get:

strtoull(-1):
         18446744073709551615 2 errno = Success
strtoll(-1):
        18446744073709551615 2 errno = Success

The functions work correctly for this case, but the result of
strtoll(-1) is displayed in a misleading form.

I get several warnings when I compile your program.  The assignments

    *endptr = input;

discard the "const" qualifier.  The solution, in this case, is to add a
cast.  That's unfortunate, but the strto*() functions, via endptr, can
give you a non-const pointer to const data.  (I'm surprised your
compiler didn't warn about this.)

You use "%lld" to print the value end-s, which is of type ptrdiff_t.
The correct format is "%td".  (Yes, I know it happens to work on your
system, but "%td" is both correct and portable.)

At the bottom of this article I've included a patch that corrects some
but not all of these problems.  (It doesn't correct the "0x" and
"-9223372036854775808" problems.)  It also shows the results of both
your functions and the implementation's standard functions.

After applying these changes, when I run your program (compiled with
-DTEST) with an argument of "0x" I get:

Strtoull(0x):
         0 0 errno = Success
Strtoll(0x):
        0 0 errno = Success
strtoull(0x):
         0 1 errno = Success
strtoll(0x):
        0 1 errno = Success

The endptr-s value is inconsistent.

With an argument of "-9223372036854775808" I get:

Strtoull(-9223372036854775808):
         9223372036854775808 20 errno = Success
Strtoll(-9223372036854775808):
        -9223372036854775808 20 errno = Numerical result out of range
strtoull(-9223372036854775808):
         9223372036854775808 20 errno = Success
strtoll(-9223372036854775808):
        -9223372036854775808 20 errno = Success

This is the ambiguous case we discussed before.
strtoll(-9223372036854775808) should, I think, return
-9223372036854775808 and set errno to 0.  (glibc's version does this.)

Here's the patch:

diff --git navia-strto.c navia-strto.c
index 664e13c..4016ba0 100644
--- navia-strto.c
+++ navia-strto.c
@@ -14,3 +14,3 @@
 
-static unsigned long long _Strtoull(const char *input,
+static unsigned long long Strtoull_(const char *input,
                       char **endptr, int base, int Flags)
@@ -32,3 +32,3 @@ static unsigned long long _Strtoull(const char *input,
        since we are going to reuse it */
-     if (endptr) *endptr = input;
+     if (endptr) *endptr = (char*)input;
 
@@ -180,3 +180,3 @@ static unsigned long long _Strtoull(const char *input,
      if (endptr != NULL && ReadSomething > 0) {
-         *endptr = input;
+         *endptr = (char*)input;
      }
@@ -200,3 +200,3 @@ unsigned long Strtol(const char *input, char **endptr, int base)
 {
-     return(_Strtoull(input, endptr, base, SIGNED32));
+     return(Strtoull_(input, endptr, base, SIGNED32));
 }
@@ -208,3 +208,3 @@ long Strtoul(const char *input, char **endptr, int base)
 {
-     return(_Strtoull(input, endptr, base, UNSIGNED32));
+     return(Strtoull_(input, endptr, base, UNSIGNED32));
 }
@@ -216,3 +216,3 @@ unsigned long long Strtoull(const char *input, char **endptr, int base)
 {
-     return(_Strtoull(input, endptr, base, UNSIGNED64));
+     return(Strtoull_(input, endptr, base, UNSIGNED64));
 }
@@ -224,3 +224,3 @@ long long Strtoll(const char *input, char **endptr, int base)
 {
-     return(_Strtoull(input, endptr, base, SIGNED64));
+     return(Strtoull_(input, endptr, base, SIGNED64));
 }
@@ -235,3 +235,3 @@ int main(int argc,char *argv[])
      char *end;
-     char *s = "-2147483647";
+     char *s;
      int save_errno;
@@ -246,12 +246,29 @@ int main(int argc,char *argv[])
          base = atoi(argv[2]);
-     errno = 0;
-     unsigned long long m = Strtoull(s,&end,0);
-     save_errno = errno;
-     printf("strtoull(%s):\n         %llu %lld",argv[1],m,end-s);
-     printf(" errno = %s\n",strerror(save_errno));
-     errno = 0;
-     m = Strtoll(s,&end,0);
-     save_errno=errno;
-     printf("strtoll(%s):\n        %llu %lld",argv[1],m,end-s);
-     printf(" errno = %s\n",strerror(save_errno));
+
+     {
+         errno = 0;
+         unsigned long long ull = Strtoull(s,&end,0);
+         save_errno = errno;
+         printf("Strtoull(%s):\n         %llu %td",argv[1],ull,end-s);
+         printf(" errno = %s\n",strerror(save_errno));
+         errno = 0;
+         long long ll = Strtoll(s,&end,0);
+         save_errno=errno;
+         printf("Strtoll(%s):\n        %lld %td",argv[1],ll,end-s);
+         printf(" errno = %s\n",strerror(save_errno));
+     }
+
+     {
+         errno = 0;
+         unsigned long long ull = strtoull(s,&end,0);
+         save_errno = errno;
+         printf("strtoull(%s):\n         %llu %td",argv[1],ull,end-s);
+         printf(" errno = %s\n",strerror(save_errno));
+         errno = 0;
+         long long ll = strtoll(s,&end,0);
+         save_errno=errno;
+         printf("strtoll(%s):\n        %lld %td",argv[1],ll,end-s);
+         printf(" errno = %s\n",strerror(save_errno));
+     }
+
 }

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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code for 32/64 bit strtoul strtol strtoull strtoll jacob navia <jacob@jacob.remcomp.fr> - 2015-03-29 17:33 +0200
  code for 32/64 bit strtoul strtol strtoull strtoll asetofsymbols@gmail.com - 2015-03-29 09:22 -0700
    Re: code for 32/64 bit strtoul strtol strtoull strtoll Barry Schwarz <schwarzb@dqel.com> - 2015-03-29 15:12 -0700
      Re: code for 32/64 bit strtoul strtol strtoull strtoll asetofsymbols@gmail.com - 2015-03-29 23:07 -0700
  Re: code for 32/64 bit strtoul strtol strtoull strtoll Barry Schwarz <schwarzb@dqel.com> - 2015-03-29 09:44 -0700
    Re: code for 32/64 bit strtoul strtol strtoull strtoll jacob navia <jacob@jacob.remcomp.fr> - 2015-03-29 19:05 +0200
      Re: code for 32/64 bit strtoul strtol strtoull strtoll Keith Thompson <kst-u@mib.org> - 2015-03-29 12:15 -0700
  Re: code for 32/64 bit strtoul strtol strtoull strtoll Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-03-30 02:01 +0100
    Re: code for 32/64 bit strtoul strtol strtoull strtoll Keith Thompson <kst-u@mib.org> - 2015-03-29 19:48 -0700
      Re: code for 32/64 bit strtoul strtol strtoull strtoll Barry Schwarz <schwarzb@dqel.com> - 2015-03-29 22:08 -0700
        Re: code for 32/64 bit strtoul strtol strtoull strtoll Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-03-30 12:44 +0100
          Re: code for 32/64 bit strtoul strtol strtoull strtoll Barry Schwarz <schwarzb@dqel.com> - 2015-03-30 09:04 -0700
            Re: code for 32/64 bit strtoul strtol strtoull strtoll Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-03-30 21:00 +0100
        Re: code for 32/64 bit strtoul strtol strtoull strtoll Keith Thompson <kst-u@mib.org> - 2015-03-30 08:24 -0700
      Re: code for 32/64 bit strtoul strtol strtoull strtoll Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-30 07:21 -0700
  Re: code for 32/64 bit strtoul strtol strtoull strtoll Ian Collins <ian-news@hotmail.com> - 2015-03-30 18:02 +1300
    Re: code for 32/64 bit strtoul strtol strtoull strtoll Richard Heathfield <rjh@cpax.org.uk> - 2015-03-30 08:03 +0100
      Re: code for 32/64 bit strtoul strtol strtoull strtoll Ian Collins <ian-news@hotmail.com> - 2015-03-30 20:33 +1300
        Re: code for 32/64 bit strtoul strtol strtoull strtoll Ian Collins <ian-news@hotmail.com> - 2015-03-30 20:35 +1300
  Re: code for 32/64 bit strtoul strtol strtoull strtoll Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-30 07:27 -0700
  Re: code for 32/64 bit strtoul strtol strtoull strtoll Keith Thompson <kst-u@mib.org> - 2015-03-30 09:08 -0700
  Re: code for 32/64 bit strtoul strtol strtoull strtoll Keith Thompson <kst-u@mib.org> - 2015-03-30 09:29 -0700
  Re: code for 32/64 bit strtoul strtol strtoull strtoll Robert Wessel <robertwessel2@yahoo.com> - 2015-03-30 15:16 -0500
    Re: code for 32/64 bit strtoul strtol strtoull strtoll jacob navia <jacob@jacob.remcomp.fr> - 2015-03-31 00:15 +0200
      Re: code for 32/64 bit strtoul strtol strtoull strtoll Robert Wessel <robertwessel2@yahoo.com> - 2015-03-31 01:42 -0500
    Re: code for 32/64 bit strtoul strtol strtoull strtoll Bartc <bc@freeuk.com> - 2015-03-30 23:39 +0100
      Re: code for 32/64 bit strtoul strtol strtoull strtoll Robert Wessel <robertwessel2@yahoo.com> - 2015-03-31 01:44 -0500
        Re: code for 32/64 bit strtoul strtol strtoull strtoll Bartc <bc@freeuk.com> - 2015-03-31 13:01 +0100
          Re: code for 32/64 bit strtoul strtol strtoull strtoll Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-31 05:13 -0700
          Re: code for 32/64 bit strtoul strtol strtoull strtoll Keith Thompson <kst-u@mib.org> - 2015-03-31 08:06 -0700
            Re: code for 32/64 bit strtoul strtol strtoull strtoll Keith Thompson <kst-u@mib.org> - 2015-03-31 08:26 -0700
            Re: code for 32/64 bit strtoul strtol strtoull strtoll Richard Heathfield <rjh@cpax.org.uk> - 2015-03-31 16:40 +0100
              Re: code for 32/64 bit strtoul strtol strtoull strtoll Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-31 09:39 -0700
              Re: code for 32/64 bit strtoul strtol strtoull strtoll Kaz Kylheku <kaz@kylheku.com> - 2015-03-31 18:22 +0000
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Richard Heathfield <rjh@cpax.org.uk> - 2015-03-31 19:36 +0100
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Keith Thompson <kst-u@mib.org> - 2015-03-31 12:11 -0700
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Kaz Kylheku <kaz@kylheku.com> - 2015-03-31 19:23 +0000
            Re: code for 32/64 bit strtoul strtol strtoull strtoll Bartc <bc@freeuk.com> - 2015-03-31 16:52 +0100
              Re: code for 32/64 bit strtoul strtol strtoull strtoll glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-03-31 17:54 +0000
                Re: code for 32/64 bit strtoul strtol strtoull strtoll raltbos@xs4all.nl (Richard Bos) - 2015-03-31 18:51 +0000
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Richard Heathfield <rjh@cpax.org.uk> - 2015-03-31 20:05 +0100
                Re: code for 32/64 bit strtoul strtol strtoull strtoll James Kuyper <jameskuyper@verizon.net> - 2015-03-31 15:18 -0400
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Richard Heathfield <rjh@cpax.org.uk> - 2015-03-31 20:49 +0100
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-31 13:06 -0700
                Re: code for 32/64 bit strtoul strtol strtoull strtoll raltbos@xs4all.nl (Richard Bos) - 2015-04-06 13:03 +0000
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Bartc <bc@freeuk.com> - 2015-04-06 14:27 +0100
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Richard Heathfield <rjh@cpax.org.uk> - 2015-04-06 17:01 +0100
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-04-06 11:25 -0700
                Re: code for 32/64 bit strtoul strtol strtoull strtoll James Kuyper <jameskuyper@verizon.net> - 2015-04-06 23:34 -0400
                Re: code for 32/64 bit strtoul strtol strtoull strtoll glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-04-07 03:46 +0000
                Re: code for 32/64 bit strtoul strtol strtoull strtoll James Kuyper <jameskuyper@verizon.net> - 2015-04-08 11:05 -0400
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-04-08 08:31 -0700
                Re: code for 32/64 bit strtoul strtol strtoull strtoll glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-03-31 19:54 +0000
                Re: code for 32/64 bit strtoul strtol strtoull strtoll James Kuyper <jameskuyper@verizon.net> - 2015-03-31 16:55 -0400
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Bartc <bc@freeuk.com> - 2015-03-31 22:20 +0100
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Keith Thompson <kst-u@mib.org> - 2015-03-31 14:36 -0700
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-31 14:55 -0700
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Keith Thompson <kst-u@mib.org> - 2015-03-31 17:00 -0700
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Bartc <bc@freeuk.com> - 2015-04-01 01:24 +0100
                Re: code for 32/64 bit strtoul strtol strtoull strtoll James Kuyper <jameskuyper@verizon.net> - 2015-03-31 23:33 -0400
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Richard Heathfield <rjh@cpax.org.uk> - 2015-04-01 04:42 +0100
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Bartc <bc@freeuk.com> - 2015-03-31 20:26 +0100
            Re: code for 32/64 bit strtoul strtol strtoull strtoll Ian Collins <ian-news@hotmail.com> - 2015-04-01 10:33 +1300
              Re: code for 32/64 bit strtoul strtol strtoull strtoll Robert Wessel <robertwessel2@yahoo.com> - 2015-04-01 04:33 -0500
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Bartc <bc@freeuk.com> - 2015-04-01 12:43 +0100
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Robert Wessel <robertwessel2@yahoo.com> - 2015-04-02 01:02 -0500
                Re: code for 32/64 bit strtoul strtol strtoull strtoll asetofsymbols@gmail.com - 2015-04-01 23:57 -0700
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Robert Wessel <robertwessel2@yahoo.com> - 2015-04-03 00:29 -0500
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-04-02 09:01 -0700
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Keith Thompson <kst-u@mib.org> - 2015-04-02 14:30 -0700
                Re: code for 32/64 bit strtoul strtol strtoull strtoll Robert Wessel <robertwessel2@yahoo.com> - 2015-04-03 00:39 -0500
                Re: code for 32/64 bit strtoul strtol strtoull strtoll glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-04-01 15:55 +0000

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