From 142f5332292a920c3ca2d6c7a712349043fc36d6 Mon Sep 17 00:00:00 2001
From: "Bryan W. Weber" <bryan.w.weber@gmail.com>
Date: Tue, 11 Jun 2019 17:14:40 -0400
Subject: [PATCH] Correct flag and libs for OpenMP on macOS

Apple's clang on macOS requires the libomp to link. Apple symlinks gcc
to clang, so it can't be detected as clang by executable name
---
 SConstruct             | 14 +++++++++++---
 samples/cxx/SConscript |  5 +++++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/SConstruct b/SConstruct
index 0567c3499..769c80554 100644
--- a/SConstruct
+++ b/SConstruct
@@ -253,7 +253,15 @@ defaults.noDebugLinkFlags = ''
 defaults.warningFlags = '-Wall'
 defaults.buildPch = False
 env['pch_flags'] = []
-env['openmp_flag'] = '-fopenmp' # used to generate sample build scripts
+env['openmp_flag'] = ['-fopenmp'] # used to generate sample build scripts
+
+env['using_apple_clang'] = False
+# Check if this is actually Apple's clang on macOS
+if env['OS'] == 'Darwin':
+    result = subprocess.check_output([env.subst('$CC'), '--version']).decode('utf-8')
+    if 'clang' in result.lower() and result.startswith('Apple LLVM'):
+        env['using_apple_clang'] = True
+        env['openmp_flag'].insert(0, '-Xpreprocessor')
 
 if 'gcc' in env.subst('$CC') or 'gnu-cc' in env.subst('$CC'):
     defaults.optimizeCcFlags += ' -Wno-inline'
@@ -276,13 +284,13 @@ elif env['CC'] == 'cl': # Visual Studio
     defaults.warningFlags = '/W3'
     defaults.buildPch = True
     env['pch_flags'] = ['/FIpch/system.h']
-    env['openmp_flag'] = '/openmp'
+    env['openmp_flag'] = ['/openmp']
 
 elif 'icc' in env.subst('$CC'):
     defaults.cxxFlags = '-std=c++0x'
     defaults.ccFlags = '-vec-report0 -diag-disable 1478'
     defaults.warningFlags = '-Wcheck'
-    env['openmp_flag'] = '-openmp'
+    env['openmp_flag'] = ['-openmp']
 
 elif 'clang' in env.subst('$CC'):
     defaults.ccFlags = '-fcolor-diagnostics'
diff --git a/samples/cxx/SConscript b/samples/cxx/SConscript
index 0d859b87f..5ce6c5f90 100644
--- a/samples/cxx/SConscript
+++ b/samples/cxx/SConscript
@@ -18,6 +18,9 @@ for subdir, name, extensions, openmp in samples:
     localenv = env.Clone()
     if openmp:
         localenv.Append(CXXFLAGS=env['openmp_flag'], LINKFLAGS=env['openmp_flag'])
+        if env['using_apple_clang']:
+            localenv.Append(LIBS=['omp'])
+
         localenv['cmake_extra'] = """
 find_package(OpenMP REQUIRED)
 set(CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS} ${OpenMP_CXX_FLAGS})
@@ -29,6 +32,8 @@ set(CMAKE_EXE_LINKER_FLAGS ${CMAKE_EXE_LINKER_FLAGS} ${OpenMP_EXE_LINKER_FLAGS})
     if env["OS"] == "Darwin":
         localenv["cmake_extra"] += "find_library(ACCELERATE_FRAMEWORK Accelerate)"
 
+    localenv.Append(LIBS=env['cantera_libs'])
+
     buildSample(localenv.Program, pjoin(subdir, name),
                 mglob(localenv, subdir, *extensions),
                 CPPPATH=['#include', env['boost_inc_dir']])