openmp/system: new recipe

recipes/openmp/all/conanfile.py

@@ -0,0 +1,127 @@
+from conan import ConanFile
+from conan.errors import ConanInvalidConfiguration
+from conan.tools.microsoft import is_msvc
+
+required_conan_version = ">=1.52.0"
+
+
+class PackageConan(ConanFile):
+    name = "openmp"
+    description = "Conan meta-package for OpenMP (Open Multi-Processing)"
+    license = "MIT"
+    url = "https://github.com/conan-io/conan-center-index"
+    homepage = "https://www.openmp.org/"
+    topics = ("parallelism", "multiprocessing")
+
+    # package_type = "meta-package"
+    settings = "os", "arch", "compiler", "build_type"
+    options = {
+        "provider": ["auto", "native", "llvm"],
+    }
+    default_options = {
+        "provider": "auto",
+    }
+
+    def config_options(self):
+        if self.settings.compiler == "clang" and self.settings.os == "Linux":
+            # The Clang toolchain on Linux distros typically ships without libomp.
+            # FreeBSD includes it, though.
+            self.options.provider = "llvm"
+        elif self.settings.compiler == "apple-clang":
+            self.options.provider = "llvm"
+        else:
+            self.options.provider = "native"
+
+    def requirements(self):
+        if self.options.provider == "llvm":
+            # Note: MSVC ships with an optional LLVM OpenMP implementation, but it would require reliably setting
+            # `OpenMP_RUNTIME_MSVC=llvm` in CMake for all consumers of this recipe, which is not possible in a meta-package.
+            # Always use the latest llvm-openmp version, since the library is ABI-compatible across versions.
+            self.requires("llvm-openmp/[*]", transitive_headers=True, transitive_libs=True)
+
+    def package_id(self):
+        self.info.clear()
+
+    def validate(self):
+        if self.options.provider == "native" and self._openmp_flags is None:
+            raise ConanInvalidConfiguration(
+                f"{self.settings.compiler} is not supported by this recipe. Contributions are welcome!"
+            )
+
+        if self.options.provider == "llvm":
+            if self.settings.compiler not in ["clang", "apple-clang"] and not is_msvc(self):
+                # More info: https://cpufun.substack.com/p/is-mixing-openmp-runtimes-safe
+                self.output.warning(
+                    "Warning: Using a non-native OpenMP implementation can be bug-prone. "
+                    "Make sure you avoid accidental linking against the native implementation through external libraries."
+                )
+
+    @property
+    def _openmp_flags(self):
+        # Based on https://github.com/Kitware/CMake/blob/v3.30.0/Modules/FindOpenMP.cmake#L119-L154
+        if self.settings.compiler == "gcc":
+            return ["-fopenmp"]
+        elif self.settings.compiler == "clang":
+            return ["-fopenmp=libomp"]
+        elif self.settings.compiler == "apple-clang":
+            return ["-Xclang", "-fopenmp"]
+        elif is_msvc(self):
+            # Use `-o provider=llvm` for `-openmp=llvm` in MSVC.
+            # TODO: add support for `-openmp=experimental`?
+            return ["-openmp"]
+        elif self.settings.compiler == "intel-cc":
+            if self.settings.os == "Windows":
+                return ["-Qopenmp"]
+            else:
+                return ["-qopenmp"]
+        elif self.settings.compiler == "sun-cc":
+            return ["-xopenmp"]
+
+        # The following compilers are not currently covered by settings.yml,
+        # but are included for completeness.
+        elif self.settings.compiler == "hp":
+            return ["+Oopenmp"]
+        elif self.settings.compiler == "intel-llvm":
+            if self.settings.get_safe("compiler.frontend") == "msvc":
+                return ["-Qiopenmp"]
+            else:
+                return ["-fiopenmp"]
+        elif self.settings.compiler == "pathscale":
+            return ["-openmp"]
+        elif self.settings.compiler == "nag":
+            return ["-openmp"]
+        elif self.settings.compiler == "absoft":
+            return ["-openmp"]
+        elif self.settings.compiler == "nvhpc":
+            return ["-mp"]
+        elif self.settings.compiler == "pgi":
+            return ["-mp"]
+        elif self.settings.compiler == "xl":
+            return ["-qsmp=omp"]
+        elif self.settings.compiler == "cray":
+            return ["-h", "omp"]
+        elif self.settings.compiler == "fujitsu":
+            return ["-Kopenmp"]
+        elif self.settings.compiler == "fujitsu-clang":
+            return ["-fopenmp"]
+
+        return None
+
+    def package_info(self):
+        # Can't use cmake_find_mode=none because Conan tries to find_package() it internally,
+        # when used transitively.
+        self.cpp_info.set_property("cmake_file_name", "_openmp_")
+
+        self.cpp_info.frameworkdirs = []
+        self.cpp_info.libdirs = []
+        self.cpp_info.resdirs = []
+        self.cpp_info.includedirs = []
+
+        if self.options.provider == "native":
+            # Export appropriate flags for packages linking against this one transitively.
+            # Direct dependencies of this package will rely on CMake's FindOpenMP.cmake instead.
+            openmp_flags = self._openmp_flags
+            self.cpp_info.sharedlinkflags = openmp_flags
+            self.cpp_info.exelinkflags = openmp_flags
+            self.cpp_info.cflags = openmp_flags
+            self.cpp_info.cxxflags = openmp_flags

recipes/openmp/all/test_package/CMakeLists.txt

@@ -0,0 +1,33 @@
+cmake_minimum_required(VERSION 3.15)
+project(PackageTest CXX C)
+
+find_package(OpenMP REQUIRED)
+
+message("OpenMP_FOUND: ${OpenMP_CXX_FOUND}")
+message("OpenMP_VERSION: ${OpenMP_VERSION}")
+message("OpenMP_C_FOUND: ${OpenMP_CXX_FOUND}")
+message("OpenMP_CXX_FOUND: ${OpenMP_CXX_FOUND}")
+message("OpenMP_CXX_VERSION: ${OpenMP_CXX_VERSION}")
+message("OpenMP_CXX_SPEC_DATE: ${OpenMP_CXX_SPEC_DATE}")
+message("OpenMP_CXX_INCLUDE_DIRS: ${OpenMP_CXX_INCLUDE_DIRS}")
+message("OpenMP_CXX_LIB_NAMES: ${OpenMP_CXX_LIB_NAMES}")
+message("OpenMP_CXX_LIBRARIES: ${OpenMP_CXX_LIBRARIES}")
+message("OpenMP_CXX_FLAGS: ${OpenMP_CXX_FLAGS}")
+message("OpenMP_omp_LIBRARY: ${OpenMP_omp_LIBRARY}")
+
+if(NOT DEFINED OpenMP_CXX_SPEC_DATE)
+    message(FATAL_ERROR "FindOpenMP.cmake did not set all variables correctly.")
+endif()
+
+add_executable(test_package_cxx test_package.cpp)
+target_link_libraries(test_package_cxx OpenMP::OpenMP_CXX)
+
+add_executable(test_package_c test_package.c)
+target_link_libraries(test_package_c OpenMP::OpenMP_C)
+
+# Using PkgConfigDeps output to test the configuration exported by package_info().
+# This is not a recommended or conventional way to use OpenMP.
+find_package(PkgConfig REQUIRED)
+pkg_check_modules(openmp REQUIRED IMPORTED_TARGET openmp)
+add_executable(test_package_pkgconfig test_package.c)
+target_link_libraries(test_package_pkgconfig PkgConfig::openmp)

recipes/openmp/all/test_package/conanfile.py

@@ -0,0 +1,41 @@
+from conan import ConanFile
+from conan.tools.build import can_run
+from conan.tools.cmake import cmake_layout, CMake
+from conan.tools.env import Environment
+import os
+
+
+class TestPackageConan(ConanFile):
+    settings = "os", "arch", "compiler", "build_type"
+    generators = "CMakeDeps", "CMakeToolchain", "PkgConfigDeps"
+
+    def requirements(self):
+        self.requires(self.tested_reference_str)
+
+    def build_requirements(self):
+        if not self.conf.get("tools.gnu:pkg_config", check_type=str):
+            self.tool_requires("pkgconf/[>=2.2 <3]")
+
+    def layout(self):
+        cmake_layout(self)
+
+    def generate(self):
+        env = Environment()
+        # Trigger printing of runtime version info on startup.
+        # Should state "LLVM OMP" as the runtime library ID if everything is configured correctly.
+        env.define("KMP_VERSION", "TRUE")
+        # Display general OpenMP parameters in a standardized format.
+        # https://www.openmp.org/spec-html/5.0/openmpse60.html
+        env.define("OMP_DISPLAY_ENV", "TRUE")
+        env.vars(self, scope="run").save_script("conan_openmp_version")
+
+    def build(self):
+        cmake = CMake(self)
+        cmake.configure()
+        cmake.build()
+
+    def test(self):
+        if can_run(self):
+            for executable in ["test_package_cxx", "test_package_c", "test_package_pkgconfig"]:
+                bin_path = os.path.join(self.cpp.build.bindir, executable)
+                self.run(bin_path, env="conanrun")

recipes/openmp/all/test_package/test_package.c

@@ -0,0 +1,26 @@
+#include <omp.h>
+
+#include <stdio.h>
+
+int main()
+{
+    int num_threads = omp_get_num_procs();
+    if (num_threads < 5)
+        num_threads = 5;
+    omp_set_num_threads(num_threads);
+    int actual_number;
+    #pragma omp parallel
+    {
+       #pragma omp single
+       {
+          actual_number = omp_get_num_threads();
+       }
+    }
+    if(actual_number != num_threads){
+        printf("Something went wrong. Expecting %d threads but found %d.\n", num_threads, actual_number);
+        printf("There are probably missing compiler flags.\n");
+        return 1;
+    }
+    printf("OpenMP API version supported by the compiler: %d\n", _OPENMP);
+    return 0;
+}

recipes/openmp/all/test_package/test_package.cpp

@@ -0,0 +1,24 @@
+#include <omp.h>
+
+#include <iostream>
+
+int main()
+{
+    int num_threads = std::max(5, omp_get_num_procs());
+    omp_set_num_threads(num_threads);
+    int actual_number;
+    #pragma omp parallel
+    {
+       #pragma omp single
+       {
+          actual_number = omp_get_num_threads();
+       }
+    }
+    if(actual_number != num_threads){
+        std::cout << "Something went wrong. Expecting " << num_threads << " threads but found " << actual_number << ".\n";
+        std::cout << "There are probably missing compiler flags.\n";
+        return 1;
+    }
+    std::cout << "OpenMP API version supported by the compiler: " << _OPENMP << "\n";
+    return 0;
+}

recipes/openmp/config.yml

@@ -0,0 +1,3 @@
+versions:
+  "system":
+    folder: all