[gcc r13-8665] libstdc++: Do not apply localized formatting to NaN and inf [PR114863]

[Jonathan Wakely via Libstdc++-cvs]

https://gcc.gnu.org/g:61c38a231d2df60cb6e914b3ecc73a0229c17ff6

commit r13-8665-g61c38a231d2df60cb6e914b3ecc73a0229c17ff6
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Fri Apr 26 11:42:26 2024 +0100

    libstdc++: Do not apply localized formatting to NaN and inf [PR114863]
    
    We don't want to add grouping to strings like "-inf", and there is no
    radix character to replace either.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/114863
            * include/std/format (__formatter_fp::format): Only use
            _M_localized for finite values.
            * testsuite/std/format/functions/format.cc: Check localized
            formatting of NaN and initiny.
    
    (cherry picked from commit 7501c0a397fcf609a1ff5f083746b6330b89ee11)

Diff:
---
 libstdc++-v3/include/std/format                       | 2 +-
 libstdc++-v3/testsuite/std/format/functions/format.cc | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index a938d65a7b9..d69703a283e 100644
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -1666,7 +1666,7 @@ namespace __format
              __str = __wstr;
            }
 
-         if (_M_spec._M_localized)
+         if (_M_spec._M_localized && __builtin_isfinite(__v))
            {
              if constexpr (is_same_v<char, _CharT>)
                __wstr = _M_localize(__str, __expc, __fc.locale());
diff --git a/libstdc++-v3/testsuite/std/format/functions/format.cc 
b/libstdc++-v3/testsuite/std/format/functions/format.cc
index 1f1802e561c..16f5cda39f1 100644
--- a/libstdc++-v3/testsuite/std/format/functions/format.cc
+++ b/libstdc++-v3/testsuite/std/format/functions/format.cc
@@ -231,6 +231,14 @@ test_locale()
   s = std::format(cloc, "{:05L}", -1.0); // PR libstdc++/110968
   VERIFY( s == "-0001" );
 
+  // PR libstdc++/114863 grouping applied to nan and inf
+  double inf = std::numeric_limits<double>::infinity();
+  s = std::format(eloc, "{0:Le} {0:Lf} {0:Lg}", -inf);
+  VERIFY( s == "-inf -inf -inf" );
+  double nan = std::numeric_limits<double>::quiet_NaN();
+  s = std::format(eloc, "{0:Le} {0:Lf} {0:Lg}", -nan);
+  VERIFY( s == "-nan -nan -nan" );
+
   // Restore
   std::locale::global(cloc);
 }