[Bug libstdc++/113512] New: Incorrect results for std::format("{:#.3g}", flt)

[Bug libstdc++/113512] New: Incorrect results for std::format("{:#.3g}", flt)

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113512

            Bug ID: 113512
           Summary: Incorrect results for std::format("{:#.3g}", flt)
           Product: gcc
           Version: 13.2.1
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

std::format("{:#.3g}", 0.02) should give 3 significant figures, i.e. "0.0200"

But libstdc++ counts the leading zeros as significant, so gives "0.02"

std::format("{:#.3g}", 0.025) should give "0.0250" but instead throws an
exception!

[Bug libstdc++/113512] Incorrect results for std::format("{:#.3g}", flt)

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113512

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |redi at gcc dot gnu.org
   Last reconfirmed|                            |2024-01-19
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
   Target Milestone|---                         |13.3

[Bug libstdc++/113512] Incorrect results for std::format("{:#.3g}", flt)

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113512

--- Comment #1 from GCC 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:a57439d61937925cec48df6166b2a805ae7054d5

commit r14-8315-ga57439d61937925cec48df6166b2a805ae7054d5
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Sat Jan 20 00:44:12 2024 +0000

    libstdc++: Fix std::format floating-point alternate forms [PR113512]

    The logic for handling '#' forms was ... not good. The count of
    significant figures just counted digits, instead of ignoring leading
    zeros. And when moving the result from the stack buffer to a dynamic
    string the exponent could get lost in some cases.

    libstdc++-v3/ChangeLog:

            PR libstdc++/113512
            * include/std/format (__formatter_fp::format): Fix logic for
            alternate forms.
            * testsuite/std/format/functions/format.cc: Check buggy cases of
            alternate forms with g presentation type.

[Bug libstdc++/113512] Incorrect results for std::format("{:#.3g}", flt)

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113512

--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Jonathan Wakely
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:1bb2e52cc69902c7bf00fbdd094e948803222946

commit r13-8261-g1bb2e52cc69902c7bf00fbdd094e948803222946
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Sat Jan 20 00:44:12 2024 +0000

    libstdc++: Fix std::format floating-point alternate forms [PR113512]

    The logic for handling '#' forms was ... not good. The count of
    significant figures just counted digits, instead of ignoring leading
    zeros. And when moving the result from the stack buffer to a dynamic
    string the exponent could get lost in some cases.

    libstdc++-v3/ChangeLog:

            PR libstdc++/113512
            * include/std/format (__formatter_fp::format): Fix logic for
            alternate forms.
            * testsuite/std/format/functions/format.cc: Check buggy cases of
            alternate forms with g presentation type.

    (cherry picked from commit a57439d61937925cec48df6166b2a805ae7054d5)

[Bug libstdc++/113512] Incorrect results for std::format("{:#.3g}", flt)

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113512

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

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

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 13.3