From 271915f641e87019fc5a3590340094822276342c Mon Sep 17 00:00:00 2001
From: Peter Urban <peter.urban@ugent.be>
Date: Wed, 10 Jan 2024 00:32:29 +0100
Subject: [PATCH] fix openmp dependency for clang-cl - see
 https://github.com/mesonbuild/meson/issues/5298

---
 mesonbuild/dependencies/misc.py          | 14 ++++++++++++--
 test cases/common/184 openmp/meson.build | 10 +++++-----
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/mesonbuild/dependencies/misc.py b/mesonbuild/dependencies/misc.py
index bec1466e9053..87d927bfca21 100644
--- a/mesonbuild/dependencies/misc.py
+++ b/mesonbuild/dependencies/misc.py
@@ -103,6 +103,7 @@ def __init__(self, environment: 'Environment', kwargs: T.Dict[str, T.Any]) -> No
             self.is_found = True
             self.compile_args = self.link_args = self.clib_compiler.openmp_flags()
             return
+
         try:
             openmp_date = self.clib_compiler.get_define(
                 '_OPENMP', '', self.env, self.clib_compiler.openmp_flags(), [self], disable_cache=True)[0]
@@ -119,13 +120,22 @@ def __init__(self, environment: 'Environment', kwargs: T.Dict[str, T.Any]) -> No
                 if openmp_date == '_OPENMP':
                     mlog.debug('This can be caused by flags such as gcc\'s `-fdirectives-only`, which affect preprocessor behavior.')
                 return
+
+            if self.clib_compiler.get_id() == 'clang-cl':
+                try:
+                    # this is necessary for clang-cl, see https://github.com/mesonbuild/meson/issues/5298
+                    self.link_args.extend(self.clib_compiler.find_library("libomp", self.env, []))
+                except:
+                    mlog.log(mlog.yellow('WARNING:'), 'OpenMP found could not find libomp necessary for clang-cl.')
+                    return
+
             # Flang has omp_lib.h
             header_names = ('omp.h', 'omp_lib.h')
             for name in header_names:
                 if self.clib_compiler.has_header(name, '', self.env, dependencies=[self], disable_cache=True)[0]:
                     self.is_found = True
-                    self.compile_args = self.clib_compiler.openmp_flags()
-                    self.link_args = self.clib_compiler.openmp_link_flags()
+                    self.compile_args.extend(self.clib_compiler.openmp_flags())
+                    self.link_args.extend(self.clib_compiler.openmp_link_flags())
                     break
             if not self.is_found:
                 mlog.log(mlog.yellow('WARNING:'), 'OpenMP found but omp.h missing.')
diff --git a/test cases/common/184 openmp/meson.build b/test cases/common/184 openmp/meson.build
index a1154c22c0c4..0bfaa0e76026 100644
--- a/test cases/common/184 openmp/meson.build	
+++ b/test cases/common/184 openmp/meson.build	
@@ -10,15 +10,15 @@ endif
 if cc.get_id() == 'msvc' and cc.version().version_compare('<17')
   error('MESON_SKIP_TEST msvc is too old to support OpenMP.')
 endif
-if cc.get_id() == 'clang-cl'
-  error('MESON_SKIP_TEST clang-cl does not support OpenMP.')
+if cc.get_id() == 'clang-cl' and cc.version().version_compare('<10.0.0')
+  error('MESON_SKIP_TEST clang-cl is too old to support OpenMP.')
 endif
 if cc.get_id() == 'clang' and host_machine.system() == 'windows'
   error('MESON_SKIP_TEST Windows clang does not support OpenMP.')
 endif
-if host_machine.system() == 'darwin'
-  error('MESON_SKIP_TEST macOS does not support OpenMP.')
-endif
+# if host_machine.system() == 'darwin'
+#   error('MESON_SKIP_TEST macOS does not support OpenMP.')
+# endif
 
 openmp = dependency('openmp')
 env = environment()