[Bug libstdc++/103911] New: std::from_chars shouldn't call isdigit

[Bug libstdc++/103911] New: std::from_chars shouldn't call isdigit

[blubban at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103911

            Bug ID: 103911
           Summary: std::from_chars shouldn't call isdigit
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: blubban at gmail dot com
  Target Milestone: ---

In header <charconv>, function __from_chars_alnum calls std::isdigit().

In addition to looking weird ("everyone" knows ctype is locale dependent and
charconv is not), this can cause trouble in a handful of rare cases.

If another thread concurrently calls setlocale, that's a race condition;
additionally, if the locale contains digits other than '0'..'9', from_chars can
return wrong answer. (For example, some versions of Windows libc think 0xB2,
0xB3 and 0xB9 are the digits ²³¹ in the "us" locale.)

GCC will, by default, replace isdigit with c>='0' && c<='9'; to reproduce the
above, use -fno-builtin or Clang.

(Bonus issue: A comment on that function says it applies to bases 11 to 26.
Shouldn't that be 11 to 36?)

[Bug libstdc++/103911] std::from_chars shouldn't call isdigit

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103911

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-01-05
     Ever confirmed|0                           |1

[Bug libstdc++/103911] std::from_chars shouldn't call isdigit

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103911

--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:c83ecfbe74a5cf107642b9c5e1680b548ff1a0e1

commit r12-6281-gc83ecfbe74a5cf107642b9c5e1680b548ff1a0e1
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Jan 5 16:25:47 2022 +0000

    libstdc++: Do not use std::isdigit in <charconv> [PR103911]

    This avoids a potential race condition if std::setlocale is used
    concurrently with std::from_chars.

    libstdc++-v3/ChangeLog:

            PR libstdc++/103911
            * include/std/charconv (__from_chars_alpha_to_num): Return
            char instead of unsigned char. Change invalid return value to
            127 instead of using numeric trait.
            (__from_chars_alnum): Fix comment. Do not use std::isdigit.
            Change type of variable to char.

[Bug libstdc++/103911] std::from_chars shouldn't call isdigit

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103911

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Thanks for the report, this is now fixed on trunk. I'll backport it too.

[Bug libstdc++/103911] std::from_chars shouldn't call isdigit

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103911

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:97f9d2f9b2a6172f31c971ac0d99ebc712b2501b

commit r11-9907-g97f9d2f9b2a6172f31c971ac0d99ebc712b2501b
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Jan 5 16:25:47 2022 +0000

    libstdc++: Do not use std::isdigit in <charconv> [PR103911]

    This avoids a potential race condition if std::setlocale is used
    concurrently with std::from_chars.

    libstdc++-v3/ChangeLog:

            PR libstdc++/103911
            * include/std/charconv (__from_chars_alpha_to_num): Return
            char instead of unsigned char. Change invalid return value to
            127 instead of using numeric trait.
            (__from_chars_alnum): Fix comment. Do not use std::isdigit.
            Change type of variable to char.

    (cherry picked from commit c83ecfbe74a5cf107642b9c5e1680b548ff1a0e1)

[Bug libstdc++/103911] std::from_chars shouldn't call isdigit

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103911

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:b596c35a4ed0143e84422449020296b43a655de7

commit r10-10560-gb596c35a4ed0143e84422449020296b43a655de7
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Jan 5 16:25:47 2022 +0000

    libstdc++: Do not use std::isdigit in <charconv> [PR103911]

    This avoids a potential race condition if std::setlocale is used
    concurrently with std::from_chars.

    libstdc++-v3/ChangeLog:

            PR libstdc++/103911
            * include/std/charconv (__from_chars_alpha_to_num): Return
            char instead of unsigned char. Change invalid return value to
            127 instead of using numeric trait.
            (__from_chars_alnum): Fix comment. Do not use std::isdigit.
            Change type of variable to char.

    (cherry picked from commit c83ecfbe74a5cf107642b9c5e1680b548ff1a0e1)

[Bug libstdc++/103911] std::from_chars shouldn't call isdigit

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103911

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |10.4
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 10.4 and 11.4, but I'm not going to bother for 9.5, so I'll close
this now. Thanks again for the report.

[Bug libstdc++/103911] std::from_chars shouldn't call isdigit

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103911

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Patrick Palka <ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:86d821ddf5615e693ead667b2580898f46de8eb9

commit r13-70-g86d821ddf5615e693ead667b2580898f46de8eb9
Author: Patrick Palka <ppalka@redhat.com>
Date:   Mon May 2 07:01:33 2022 -0400

    libstdc++: Don't use std::tolower in <charconv> [PR103911]

    As with std::isdigit in r12-6281-gc83ecfbe74a5cf, we shouldn't be using
    std::tolower in <charconv> either.

            PR libstdc++/103911

    libstdc++-v3/ChangeLog:

            * src/c++17/floating_from_chars.cc (find_end_of_float): Accept
            two delimeters for the exponent part in the form of a possibly
            NULL string of length two.  Don't use std::tolower.
            (pattern): Adjust calls to find_end_of_float accordingly.

[Bug libstdc++/103911] std::from_chars shouldn't call isdigit

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103911

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:eed2cd48cd5e8d94ceb15c5fd86cdd27926b54b5

commit r12-8349-geed2cd48cd5e8d94ceb15c5fd86cdd27926b54b5
Author: Patrick Palka <ppalka@redhat.com>
Date:   Mon May 2 07:01:33 2022 -0400

    libstdc++: Don't use std::tolower in <charconv> [PR103911]

    As with std::isdigit in r12-6281-gc83ecfbe74a5cf, we shouldn't be using
    std::tolower in <charconv> either.

            PR libstdc++/103911

    libstdc++-v3/ChangeLog:

            * src/c++17/floating_from_chars.cc (find_end_of_float): Accept
            two delimeters for the exponent part in the form of a possibly
            NULL string of length two.  Don't use std::tolower.
            (pattern): Adjust calls to find_end_of_float accordingly.

    (cherry picked from commit 86d821ddf5615e693ead667b2580898f46de8eb9)

[Bug libstdc++/103911] std::from_chars shouldn't call isdigit

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103911

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Patrick Palka
<ppalka@gcc.gnu.org>:

https://gcc.gnu.org/g:39099827b0f731b5f2da696f6f580156c8a7819c

commit r11-9979-g39099827b0f731b5f2da696f6f580156c8a7819c
Author: Patrick Palka <ppalka@redhat.com>
Date:   Mon May 2 07:01:33 2022 -0400

    libstdc++: Don't use std::tolower in <charconv> [PR103911]

    As with std::isdigit in r12-6281-gc83ecfbe74a5cf, we shouldn't be using
    std::tolower in <charconv> either.

            PR libstdc++/103911

    libstdc++-v3/ChangeLog:

            * src/c++17/floating_from_chars.cc (find_end_of_float): Accept
            two delimeters for the exponent part in the form of a possibly
            NULL string of length two.  Don't use std::tolower.
            (pattern): Adjust calls to find_end_of_float accordingly.

    (cherry picked from commit 86d821ddf5615e693ead667b2580898f46de8eb9)