llvm-openmp: make the wrapper slightly more robust

Based on microsoft/vcpkg#39389

recipes/llvm-openmp/all/cmake/conan-llvm-openmp-vars.cmake.in

@@ -33,9 +33,15 @@ function(_openmp_get_compiler_spec_date)
   set(BIN_FILE "${BUILD_DIR}/ompver.bin")
   file(WRITE "${SRC_FILE}" "
     #include <stdio.h>
-    #define STRINGIFY(x) #x
-    #define TO_STRING(x) STRINGIFY(x)
-    const char ompver_str[] = \"INFO:OpenMP-date[\" TO_STRING(_OPENMP) \"]\";
+    const char ompver_str[] = { 'I', 'N', 'F', 'O', ':', 'O', 'p', 'e', 'n', 'M',
+                                'P', '-', 'd', 'a', 't', 'e', '[',
+                                ('0' + ((_OPENMP/100000)%10)),
+                                ('0' + ((_OPENMP/10000)%10)),
+                                ('0' + ((_OPENMP/1000)%10)),
+                                ('0' + ((_OPENMP/100)%10)),
+                                ('0' + ((_OPENMP/10)%10)),
+                                ('0' + ((_OPENMP/1)%10)),
+                                ']', '\\0' };
     int main(void)
     {
       puts(ompver_str);
@@ -44,7 +50,9 @@ function(_openmp_get_compiler_spec_date)
   ")
   try_compile(OpenMP_SPECTEST ${BUILD_DIR}
     SOURCES "${SRC_FILE}"
-    COMPILE_DEFINITIONS "${OpenMP_C_FLAGS}"
+    CMAKE_FLAGS
+      "-DCOMPILE_DEFINITIONS:STRING=${OpenMP_C_FLAGS}"
+      "-DINCLUDE_DIRECTORIES:STRING=${OpenMP_C_INCLUDE_DIR}"
     COPY_FILE "${BIN_FILE}"
   )
   if(NOT OpenMP_SPECTEST)
@@ -72,17 +80,25 @@ function(_openmp_set_version_by_spec_date)
   set(OpenMP_SPEC_DATE_MAP
     "202111=5.2"
     "202011=5.1"
+    # Preview versions
+    "201611=5.0" # OpenMP 5.0 preview 1
+    # Combined versions, 2.5 onwards
     "201811=5.0"
     "201611=5.0"
     "201511=4.5"
     "201307=4.0"
     "201107=3.1"
     "200805=3.0"
     "200505=2.5"
+    # C/C++ version 2.0
     "200203=2.0"
+    # Fortran version 2.0
     "200011=2.0"
+    # Fortran version 1.1
     "199911=1.1"
+    # C/C++ version 1.0 (there's no 1.1 for C/C++)
     "199810=1.0"
+    # Fortran version 1.0
     "199710=1.0"
   )
   if(OpenMP_SPEC_DATE_MAP MATCHES "${OpenMP_SPEC_DATE}=([0-9]+)\\.([0-9]+)")
@@ -103,34 +119,30 @@ endfunction()
 
 # Compare the OpenMP API version supported by the compiler to
 # the version supported by the LLVM OMP runtime and use the lower of the two.
-# Note that this differs from the CMake's FindOpenMP.cmake implementation,
-# which checks only the version supported by the compiler, and appears to be an oversight on CMake's part.
+# Note that this differs slightly from the CMake's FindOpenMP.cmake implementation,
+# which checks only the version supported by the compiler.
 _openmp_get_compiler_spec_date()
 if(OpenMP_SPEC_DATE GREATER @OpenMP_SPEC_DATE@)
-    set(OpenMP_SPEC_DATE @OpenMP_SPEC_DATE@)
-    set(OpenMP_VERSION_MAJOR @OpenMP_VERSION_MAJOR@)
-    set(OpenMP_VERSION_MINOR @OpenMP_VERSION_MINOR@)
-    set(OpenMP_VERSION @OpenMP_VERSION@)
+  set(OpenMP_SPEC_DATE @OpenMP_SPEC_DATE@)
+  set(OpenMP_VERSION_MAJOR @OpenMP_VERSION_MAJOR@)
+  set(OpenMP_VERSION_MINOR @OpenMP_VERSION_MINOR@)
+  set(OpenMP_VERSION @OpenMP_VERSION@)
 else()
-    _openmp_set_version_by_spec_date()
+  _openmp_set_version_by_spec_date()
 endif()
 
-set(OpenMP_C_FOUND TRUE)
-set(OpenMP_C_SPEC_DATE "${OpenMP_SPEC_DATE}")
-set(OpenMP_C_VERSION_MAJOR "${OpenMP_VERSION_MAJOR}")
-set(OpenMP_C_VERSION_MINOR "${OpenMP_VERSION_MINOR}")
-set(OpenMP_C_VERSION "${OpenMP_VERSION}")
-
-set(OpenMP_CXX_FOUND TRUE)
-set(OpenMP_CXX_SPEC_DATE "${OpenMP_SPEC_DATE}")
-set(OpenMP_CXX_VERSION_MAJOR "${OpenMP_VERSION_MAJOR}")
-set(OpenMP_CXX_VERSION_MINOR "${OpenMP_VERSION_MINOR}")
-set(OpenMP_CXX_VERSION "${OpenMP_VERSION}")
+foreach(_lang C CXX)
+  set(OpenMP_${_lang}_FOUND TRUE)
+  set(OpenMP_${_lang}_SPEC_DATE "${OpenMP_SPEC_DATE}")
+  set(OpenMP_${_lang}_VERSION_MAJOR "${OpenMP_VERSION_MAJOR}")
+  set(OpenMP_${_lang}_VERSION_MINOR "${OpenMP_VERSION_MINOR}")
+  set(OpenMP_${_lang}_VERSION "${OpenMP_VERSION}")
+endforeach()
 
 # Check specification version against the requested min version, validate components
 include(FindPackageHandleStandardArgs)
 find_package_handle_standard_args(OpenMP
-  VERSION_VAR OpenMP_C_VERSION
+  VERSION_VAR OpenMP_VERSION
   REQUIRED_VARS
     OpenMP_C_FLAGS
     OpenMP_C_LIB_NAMES
@@ -142,7 +154,6 @@ find_package_handle_standard_args(OpenMP
     OpenMP_CXX_VERSION
   HANDLE_COMPONENTS
 )
-
 set(OPENMP_FOUND ${OpenMP_FOUND})
 set(OpenMP_C_FOUND ${OpenMP_FOUND})
 set(OpenMP_CXX_FOUND ${OpenMP_FOUND})