libstdc++: Check _GLIBCXX_USE_C99_STDLIB for strtof and strtold

On broken systems we only have strtod, not strtof and strtold. Just use
strtod for all types, even though that will produce incorrect results in
some cases.

Similarly, if _GLIBCXX_USE_C99_MATH is not defined then std::isinf won't
be declared. Just refer to it unqualified, which should find the C
library's isinf macro if that hasn't been #undef'd by <cmath>.

libstdc++-v3/ChangeLog:

	* src/c++17/floating_from_chars.cc (from_chars_impl): Use
	isinf unqualified.
	[!_GLIBCXX_USE_C99_STDLIB]: Use strtod for float and long
	double.

diff --git a/libstdc++-v3/src/c++17/floating_from_chars.cc b/libstdc++-v3/src/c++17/floating_from_chars.cc
index f1519e5c7b6abc4390b541fd14a746d3e6078a45..26b69a3852150f6f2b07116e48a392fe1c6d5120 100644 (file)
--- a/libstdc++-v3/src/c++17/floating_from_chars.cc
+++ b/libstdc++-v3/src/c++17/floating_from_chars.cc
@@ -300,12 +300,16 @@ namespace
        errno = 0;
        char* endptr;
        T tmpval;
+#if _GLIBCXX_USE_C99_STDLIB
        if constexpr (is_same_v<T, float>)
          tmpval = std::strtof(str, &endptr);
-       if constexpr (is_same_v<T, double>)
+       else if constexpr (is_same_v<T, double>)
          tmpval = std::strtod(str, &endptr);
        else if constexpr (is_same_v<T, long double>)
          tmpval = std::strtold(str, &endptr);
+#else
+       tmpval = std::strtod(str, &endptr);
+#endif
        const int conv_errno = std::__exchange(errno, save_errno);
 
 #if _GLIBCXX_USE_C99_FENV_TR1
@@ -319,7 +323,7 @@ namespace
        const ptrdiff_t n = endptr - str;
        if (conv_errno == ERANGE) [[unlikely]]
          {
-           if (std::isinf(tmpval)) // overflow
+           if (isinf(tmpval)) // overflow
              ec = errc::result_out_of_range;
            else // underflow (LWG 3081 wants to set value = tmpval here)
              ec = errc::result_out_of_range;