[gcc r14-2635] libstdc++: Check autoconf macros for strtof and strtold [PR110653]

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:58303d42809f0e01f23262f592d37943f7703f71

commit r14-2635-g58303d42809f0e01f23262f592d37943f7703f71
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Jul 13 10:44:57 2023 +0100

    libstdc++: Check autoconf macros for strtof and strtold [PR110653]
    
    As well as the _GLIBCXX_USE_C99_STDLIB check, we also have a separate
    check in linkage.m4 for just strtof and strtold. We can use that to
    declare std::strtof and std::strtold in <cstdlib> for additional
    targets. That allows us to enable std::stold on hpux11.11 which is
    missing strtoll, strtoull and strtof, so doesn't define
    _GLIBCXX_USE_C99_STDLIB. Although it doesn't help hpux11.11, we can
    define std::stof for more targets this way too.
    
    As with the previous commit for PR110653, this only affects the narrow
    character overloads. std::stof and std::stold for wstring still requires
    C99 <wchar.h> support.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/110653
            * include/bits/basic_string.h [_GLIBCXX_HAVE_STRTOF] (stof):
            Define.
            [_GLIBCXX_HAVE_STRTOLD] (stold): Define.
            * include/c_global/cstdlib [_GLIBCXX_HAVE_STRTOF] (strtof):
            Declare in namespace std.
            [_GLIBCXX_HAVE_STRTOLD] (strtold): Likewise.

Diff:
---
 libstdc++-v3/include/bits/basic_string.h |  6 ++++--
 libstdc++-v3/include/c_global/cstdlib    | 14 ++++++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/include/bits/basic_string.h b/libstdc++-v3/include/bits/basic_string.h
index 01e25dad20e..32f5d4421f7 100644
--- a/libstdc++-v3/include/bits/basic_string.h
+++ b/libstdc++-v3/include/bits/basic_string.h
@@ -4148,12 +4148,14 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
   stod(const string& __str, size_t* __idx = 0)
   { return __gnu_cxx::__stoa(&std::strtod, "stod", __str.c_str(), __idx); }
 
-#if _GLIBCXX_USE_C99_STDLIB
+#if _GLIBCXX_USE_C99_STDLIB || _GLIBCXX_HAVE_STRTOF
   // NB: strtof vs strtod.
   inline float
   stof(const string& __str, size_t* __idx = 0)
   { return __gnu_cxx::__stoa(&std::strtof, "stof", __str.c_str(), __idx); }
+#endif
 
+#if _GLIBCXX_USE_C99_STDLIB || _GLIBCXX_HAVE_STRTOLD
   inline long double
   stold(const string& __str, size_t* __idx = 0)
   { return __gnu_cxx::__stoa(&std::strtold, "stold", __str.c_str(), __idx); }
@@ -4161,7 +4163,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
   inline long double
   stold(const string& __str, size_t* __idx = 0)
   { return std::stod(__str, __idx); }
-#endif // _GLIBCXX_USE_C99_STDLIB
+#endif
 
   // DR 1261. Insufficent overloads for to_string / to_wstring
 
diff --git a/libstdc++-v3/include/c_global/cstdlib b/libstdc++-v3/include/c_global/cstdlib
index aeb961ad69d..60317aa9a4a 100644
--- a/libstdc++-v3/include/c_global/cstdlib
+++ b/libstdc++-v3/include/c_global/cstdlib
@@ -256,6 +256,20 @@ namespace std
   using ::__gnu_cxx::strtold;
 } // namespace std
 
+#else  // ! _GLIBCXX_USE_C99_STDLIB
+
+// We also check for strtof and strtold separately from _GLIBCXX_USE_C99_STDLIB
+
+#if _GLIBCXX_HAVE_STRTOF
+#undef strtof
+namespace std { using ::strtof; }
+#endif
+
+#if _GLIBCXX_HAVE_STRTOLD
+#undef strtold
+namespace std { using ::strtold; }
+#endif
+
 #endif // _GLIBCXX_USE_C99_STDLIB
 
 } // extern "C++"