[committed] libstdc++: Do not apply localized formatting to NaN and inf [PR114863]

[committed] libstdc++: Do not apply localized formatting to NaN and inf [PR114863]

[Jonathan Wakely]

Tested x86_64-linux. Pushed to trunk.

I'm going to push this to gcc-13 and gcc-14 too (approved by Jakub on
IRC).

-- >8 --

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.
---
 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 22dcb5f24bd..48deba2bcb2 100644
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -1734,7 +1734,7 @@ namespace __format
 	    }
 #endif
 
-	  if (_M_spec._M_localized)
+	  if (_M_spec._M_localized && __builtin_isfinite(__v))
 	    {
 	      __wstr = _M_localize(__str, __expc, __fc.locale());
 	      if (!__wstr.empty())
diff --git a/libstdc++-v3/testsuite/std/format/functions/format.cc b/libstdc++-v3/testsuite/std/format/functions/format.cc
index 4499397aaf9..78cc1ab482a 100644
--- a/libstdc++-v3/testsuite/std/format/functions/format.cc
+++ b/libstdc++-v3/testsuite/std/format/functions/format.cc
@@ -248,6 +248,14 @@ 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);
 }
-- 
2.44.0