[flang][runtime] Fixed flang+Werror buildbots after #83169.

Author: vzakhari

flang/include/flang/Common/float128.h

@@ -54,9 +54,13 @@
 /* Define pure C CFloat128Type and CFloat128ComplexType. */
 #if LDBL_MANT_DIG == 113
 typedef long double CFloat128Type;
+#ifndef __cplusplus
 typedef long double _Complex CFloat128ComplexType;
+#endif
 #elif HAS_FLOAT128
 typedef __float128 CFloat128Type;
+
+#ifndef __cplusplus
 /*
  * Use mode() attribute supported by GCC and Clang.
  * Adjust it for other compilers as needed.
@@ -66,5 +70,6 @@ typedef _Complex float __attribute__((mode(TC))) CFloat128ComplexType;
 #else
 typedef _Complex float __attribute__((mode(KC))) CFloat128ComplexType;
 #endif
+#endif // __cplusplus
 #endif
 #endif /* FORTRAN_COMMON_FLOAT128_H_ */

flang/runtime/Float128Math/cabs.cpp

@@ -10,13 +10,15 @@
 
 namespace Fortran::runtime {
 extern "C" {
-
+#if 0
+// FIXME: temporarily disabled. Need to add pure C entry point
+// using C _Complex ABI.
 #if LDBL_MANT_DIG == 113 || HAS_FLOAT128
 // NOTE: Flang calls the runtime APIs using C _Complex ABI
 CppTypeFor<TypeCategory::Real, 16> RTDEF(CAbsF128)(CFloat128ComplexType x) {
   return CAbs<RTNAME(CAbsF128)>::invoke(x);
 }
 #endif
-
+#endif
 } // extern "C"
 } // namespace Fortran::runtime

flang/runtime/Float128Math/math-entries.h

@@ -61,7 +61,6 @@ DEFINE_FALLBACK(Asinh)
 DEFINE_FALLBACK(Atan)
 DEFINE_FALLBACK(Atan2)
 DEFINE_FALLBACK(Atanh)
-DEFINE_FALLBACK(CAbs)
 DEFINE_FALLBACK(Ceil)
 DEFINE_FALLBACK(Cos)
 DEFINE_FALLBACK(Cosh)
@@ -163,7 +162,6 @@ DEFINE_SIMPLE_ALIAS(Asinh, asinhq)
 DEFINE_SIMPLE_ALIAS(Atan, atanq)
 DEFINE_SIMPLE_ALIAS(Atan2, atan2q)
 DEFINE_SIMPLE_ALIAS(Atanh, atanhq)
-DEFINE_SIMPLE_ALIAS(CAbs, cabsq)
 DEFINE_SIMPLE_ALIAS(Ceil, ceilq)
 DEFINE_SIMPLE_ALIAS(Cos, cosq)
 DEFINE_SIMPLE_ALIAS(Cosh, coshq)