Fix return type of isinf(double) and isnan(double) where possible.

When using an old version of glibc, a ::isinf(double) and ::isnan(double)
function is provided, rather than just the macro required by C and C++.
Displace this function using _LIBCPP_PREFERRED_OVERLOAD where possible.

The only remaining case where we should get the wrong return type is now
glibc + libc++ + a non-clang compiler.

llvm-svn: 331241

2 files changed, 36 insertions, 6 deletions

diff --git a/libcxx/include/math.h b/libcxx/include/math.h
index cd055caef72..658ba93be01 100644
--- a/libcxx/include/math.h
+++ b/libcxx/include/math.h
@@ -483,6 +483,20 @@ typename std::enable_if<
 isinf(_A1) _NOEXCEPT
 { return false; }
 
+#ifdef _LIBCPP_PREFERRED_OVERLOAD
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+isinf(float __lcpp_x) _NOEXCEPT { return __libcpp_isinf(__lcpp_x); }
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_PREFERRED_OVERLOAD
+bool
+isinf(double __lcpp_x) _NOEXCEPT { return __libcpp_isinf(__lcpp_x); }
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+isinf(long double __lcpp_x) _NOEXCEPT { return __libcpp_isinf(__lcpp_x); }
+#endif
+
 #endif  // isinf
 
 // isnan
@@ -513,6 +527,20 @@ typename std::enable_if<std::is_integral<_A1>::value, bool>::type
 isnan(_A1) _NOEXCEPT
 { return false; }
 
+#ifdef _LIBCPP_PREFERRED_OVERLOAD
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+isnan(float __lcpp_x) _NOEXCEPT { return __libcpp_isnan(__lcpp_x); }
+
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_PREFERRED_OVERLOAD
+bool
+isnan(double __lcpp_x) _NOEXCEPT { return __libcpp_isnan(__lcpp_x); }
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+isnan(long double __lcpp_x) _NOEXCEPT { return __libcpp_isnan(__lcpp_x); }
+#endif
+
 #endif  // isnan
 
 // isnormal
diff --git a/libcxx/test/std/numerics/c.math/cmath.pass.cpp b/libcxx/test/std/numerics/c.math/cmath.pass.cpp
index b5f586492bd..cc535e37439 100644
--- a/libcxx/test/std/numerics/c.math/cmath.pass.cpp
+++ b/libcxx/test/std/numerics/c.math/cmath.pass.cpp
@@ -661,11 +661,12 @@ void test_isinf()
     static_assert((std::is_same<decltype(std::isinf((float)0)), bool>::value), "");
 
     typedef decltype(std::isinf((double)0)) DoubleRetType;
-#ifndef __linux__
+#if !defined(__linux__) || defined(__clang__)
     static_assert((std::is_same<DoubleRetType, bool>::value), "");
 #else
-    // GLIBC < 2.26 defines 'isinf(double)' with a return type of 'int' in
-    // all C++ dialects. The test should tolerate this.
+    // GLIBC < 2.23 defines 'isinf(double)' with a return type of 'int' in
+    // all C++ dialects. The test should tolerate this when libc++ can't work
+    // around it.
     // See: https://sourceware.org/bugzilla/show_bug.cgi?id=19439
     static_assert((std::is_same<DoubleRetType, bool>::value
                 || std::is_same<DoubleRetType, int>::value), "");
@@ -746,11 +747,12 @@ void test_isnan()
     static_assert((std::is_same<decltype(std::isnan((float)0)), bool>::value), "");
 
     typedef decltype(std::isnan((double)0)) DoubleRetType;
-#ifndef __linux__
+#if !defined(__linux__) || defined(__clang__)
     static_assert((std::is_same<DoubleRetType, bool>::value), "");
 #else
-    // GLIBC < 2.26 defines 'isnan(double)' with a return type of 'int' in
-    // all C++ dialects. The test should tolerate this.
+    // GLIBC < 2.23 defines 'isinf(double)' with a return type of 'int' in
+    // all C++ dialects. The test should tolerate this when libc++ can't work
+    // around it.
     // See: https://sourceware.org/bugzilla/show_bug.cgi?id=19439
     static_assert((std::is_same<DoubleRetType, bool>::value
                 || std::is_same<DoubleRetType, int>::value), "");