[flang-commits] [flang] [flang] Fix Darwin build after 4762c6557d15 (PR #84478)

[Leandro Lupori via flang-commits]

https://github.com/luporl updated https://github.com/llvm/llvm-project/pull/84478

>From 870baf788c5a21252d3a2d1958af26f5b80f0cb9 Mon Sep 17 00:00:00 2001
From: Leandro Lupori <leandro.lupori at linaro.org>
Date: Fri, 8 Mar 2024 09:55:49 -0300
Subject: [PATCH] [flang] Fix Darwin build after 4762c6557d15

Select POSIX 2008 standard to avoid including Darwin extensions.
Otherwise, Darwin's math.h header defines HUGE, which conflicts
with Flang's HUGE function.

This started happening after 4762c6557d15 (#82443), that added the
"utility" include, which seems to include "math.h".
---
 flang/CMakeLists.txt                      | 8 ++++++++
 flang/include/flang/Evaluate/integer.h    | 4 ----
 flang/include/flang/Evaluate/real.h       | 4 ----
 flang/lib/Evaluate/fold-implementation.h  | 4 ----
 flang/lib/Evaluate/intrinsics-library.cpp | 4 ++--
 5 files changed, 10 insertions(+), 14 deletions(-)

diff --git a/flang/CMakeLists.txt b/flang/CMakeLists.txt
index 21617aeea0215e..71141e5efac488 100644
--- a/flang/CMakeLists.txt
+++ b/flang/CMakeLists.txt
@@ -413,6 +413,14 @@ if (LLVM_COMPILER_IS_GCC_COMPATIBLE)
 
 endif()
 
+# Clang on Darwin enables non-POSIX extensions by default, which allows the
+# macro HUGE to leak out of <math.h> even when it is never directly included,
+# conflicting with Flang's HUGE symbols.
+# Set _POSIX_C_SOURCE to avoid including these extensions.
+if (APPLE)
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -D_POSIX_C_SOURCE=200809")
+endif()
+
 list(REMOVE_DUPLICATES CMAKE_CXX_FLAGS)
 
 # Determine HOST_LINK_VERSION on Darwin.
diff --git a/flang/include/flang/Evaluate/integer.h b/flang/include/flang/Evaluate/integer.h
index 2fce4bedfaee0f..977d35c7eecf48 100644
--- a/flang/include/flang/Evaluate/integer.h
+++ b/flang/include/flang/Evaluate/integer.h
@@ -27,10 +27,6 @@
 #include <string>
 #include <type_traits>
 
-// Some environments, viz. clang on Darwin, allow the macro HUGE
-// to leak out of <math.h> even when it is never directly included.
-#undef HUGE
-
 namespace Fortran::evaluate::value {
 
 // Implements an integer as an assembly of smaller host integer parts
diff --git a/flang/include/flang/Evaluate/real.h b/flang/include/flang/Evaluate/real.h
index 62c99cebc31684..5266bd0ef64bfd 100644
--- a/flang/include/flang/Evaluate/real.h
+++ b/flang/include/flang/Evaluate/real.h
@@ -18,10 +18,6 @@
 #include <limits>
 #include <string>
 
-// Some environments, viz. clang on Darwin, allow the macro HUGE
-// to leak out of <math.h> even when it is never directly included.
-#undef HUGE
-
 namespace llvm {
 class raw_ostream;
 }
diff --git a/flang/lib/Evaluate/fold-implementation.h b/flang/lib/Evaluate/fold-implementation.h
index 798bc5f37f6f42..6b3c9416724cb6 100644
--- a/flang/lib/Evaluate/fold-implementation.h
+++ b/flang/lib/Evaluate/fold-implementation.h
@@ -39,10 +39,6 @@
 #include <type_traits>
 #include <variant>
 
-// Some environments, viz. clang on Darwin, allow the macro HUGE
-// to leak out of <math.h> even when it is never directly included.
-#undef HUGE
-
 namespace Fortran::evaluate {
 
 // Utilities
diff --git a/flang/lib/Evaluate/intrinsics-library.cpp b/flang/lib/Evaluate/intrinsics-library.cpp
index e68c5ed3f6a8b1..7315a7a057b102 100644
--- a/flang/lib/Evaluate/intrinsics-library.cpp
+++ b/flang/lib/Evaluate/intrinsics-library.cpp
@@ -299,8 +299,8 @@ struct HostRuntimeLibrary<std::complex<HostT>, LibraryVersion::Libm> {
 /// Define libm extensions
 /// Bessel functions are defined in POSIX.1-2001.
 
-// Remove float bessel functions for AIX as they are not supported
-#ifndef _AIX
+// Remove float bessel functions for AIX and Darwin as they are not supported
+#if !defined(_AIX) && !defined(__APPLE__)
 template <> struct HostRuntimeLibrary<float, LibraryVersion::LibmExtensions> {
   using F = FuncPointer<float, float>;
   using FN = FuncPointer<float, int, float>;