C2x strtol binary constant handling: Fix special case "0b"

[Bruno Haible <bruno@clisp.org>]

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Hi Joseph,

While adding C2x support to the strtol, strtoll, strtoul, strtoull
functions in Gnulib, I was glad to see that you have already done
the support in glibc. But I noticed that the glibc implementation
apparently does not handle the input "0b" correctly. The unit test
cases for this special case are:

  {
    const char input[] = "0b";
    char *ptr;
    long result;
    errno = 0;
    result = strtol (input, &ptr, 2);
    assert (result == 0L);
    assert (ptr == input + 1);
    assert (errno == 0);
  }
  {
    const char input[] = "0b";
    char *ptr;
    long result;
    errno = 0;
    result = strtol (input, &ptr, 0);
    assert (result == 0L);
    assert (ptr == input + 1);
    assert (errno == 0);
  }

and likewise for strtoll, strtoul, strtoull.

Find attached a correction for this. I have tested it in Gnulib (which
has very similar source code as glibc for this functionality), not in
Glibc directly. Therefore, please review thoroughly.

Bruno

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From c11497ab8117f27680537abccda211c5be560452 Mon Sep 17 00:00:00 2001
From: Bruno Haible <bruno@clisp.org>
Date: Thu, 16 Mar 2023 15:25:45 +0100
Subject: [PATCH] C2x strtol binary constant handling: Fix special case "0b".

This is a follow-up to commit 64924422a99690d147a166b4de3103f3bf3eaf6c
by Joseph Myers.

The special case of input "0b" was not handled correctly. Test cases:

  {
    const char input[] = "0b";
    char *ptr;
    long result;
    errno = 0;
    result = strtol (input, &ptr, 2);
    assert (result == 0L);
    assert (ptr == input + 1);
    assert (errno == 0);
  }
  {
    const char input[] = "0b";
    char *ptr;
    long result;
    errno = 0;
    result = strtol (input, &ptr, 0);
    assert (result == 0L);
    assert (ptr == input + 1);
    assert (errno == 0);
  }

* stdlib/strtol_l.c (INTERNAL (__strtol_l)): Handle the binary integers
also in the 'noconv' part of the code.
---
 stdlib/strtol_l.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/stdlib/strtol_l.c b/stdlib/strtol_l.c
index 3424c3feab..548b46aa52 100644
--- a/stdlib/strtol_l.c
+++ b/stdlib/strtol_l.c
@@ -526,11 +526,15 @@ INTERNAL (__strtol_l) (const STRING_TYPE *nptr, STRING_TYPE **endptr,
 noconv:
   /* We must handle a special case here: the base is 0 or 16 and the
      first two characters are '0' and 'x', but the rest are no
-     hexadecimal digits.  This is no error case.  We return 0 and
-     ENDPTR points to the `x`.  */
+     hexadecimal digits.  Likewise when the base is 0 or 2 and the
+     first two characters are '0' and 'b', but the rest are no binary
+     digits.  This is no error case.  We return 0 and ENDPTR points to
+     the 'x' or 'b'.  */
   if (endptr != NULL)
     {
-      if (save - nptr >= 2 && TOUPPER (save[-1]) == L_('X')
+      if (save - nptr >= 2
+	  && (TOUPPER (save[-1]) == L_('X')
+	      || (bin_cst && TOUPPER (save[-1]) == L_('B')))
 	  && save[-2] == L_('0'))
 	*endptr = (STRING_TYPE *) &save[-1];
       else
-- 
2.34.1