feat(openmp): add OpenMP compatibility package and tests

.agents/docs/2026-10-13-add-openmp-plan.md

@@ -0,0 +1,31 @@
+# Add compat.openmp
+
+LLVM libomp 22.1.8 is a separable CMake project inside llvm-project.
+The descriptor downloads the full official llvm-project-22.1.8.src.tar.xz,
+whose SHA-256 was checked twice; license Apache-2.0 WITH LLVM-exception.
+The install hook builds upstream openmp/ and installs the generated omp.h
+and real runtime. It writes the C anchor only after installation succeeds.
+
+Unix uses static libomp.a, which implements both Clang and GCC OpenMP ABIs
+without a C++ standard-library ABI dependency. The hook uses the system C/C++
+SDK explicitly because installation precedes mcpp consumer toolchain selection.
+Windows uses the upstream-supported DLL/import library with Visual Studio 2022;
+the DLL is declared as a runtime artifact directory for consumer deployment.
+The Visual Studio generator can omit the archive for upstream's source-less
+ompimp target. In that case the hook installs the import library produced by
+the DLL link under the expected libomp.lib name; DLL and imports are from the
+same build. Windows CMake commands run through a batch file, preserving quoted
+SDK paths and propagating failures with the build log tail.
+CMake and Python are declared build dependencies. Offloading and OMPT tools
+are disabled; there is no misleading sources-only feature for these builds.
+
+No mirror upload was performed. Plain-string GLOBAL URLs provide CN fallback.
+The example redirects compat to this checkout. It enables OpenMP with normal
+GCC/Clang flags (Apple Clang uses -Xclang -fopenmp), links the package runtime,
+launches two threads, and checks thread identity plus a reduction sum. The
+header never defines _OPENMP: a missing compiler flag is a compile error.
+
+Local validation with CI-pinned mcpp 2026.10.1.2 and gcc 16.1.0:
+`mcpp test -p openmp`: `test result ok. 1 passed; 0 failed`.
+An independent upstream CMake build also succeeded. Cross-platform behavior
+is validated by the PR CI matrix rather than inferred from a SIMD-only test.

README.md

@@ -42,7 +42,7 @@ One descriptor per common shape:
 | Generated config header | [`compat.c-ares`](pkgs/c/compat.c-ares.lua) |
 | C++23 module wrapper | [`nlohmann.json`](pkgs/n/nlohmann.json.lua) |
 | C++23 module shipped by upstream | [`khronos.vulkan-hpp`](pkgs/k/khronos.vulkan-hpp.lua) |
-| External build system (`install()`) | [`compat.openssl`](pkgs/c/compat.openssl.lua) |
+| External build system (`install()`) | [`compat.openssl`](pkgs/c/compat.openssl.lua) · [`compat.openmp`](pkgs/c/compat.openmp.lua) |
 
 Every other shape, and why each descriptor is written the way it is, is in
 **[Descriptor examples by shape](docs/descriptor-examples.md)**.

README.zh-CN.md

@@ -41,7 +41,7 @@ mcpp self config --mirror CN   # 切换至国内镜像,默认使用 GLOBAL 上
 | 生成 config 头 | [`compat.c-ares`](pkgs/c/compat.c-ares.lua) |
 | C++23 module wrapper | [`nlohmann.json`](pkgs/n/nlohmann.json.lua) |
 | 上游自带 C++23 module | [`khronos.vulkan-hpp`](pkgs/k/khronos.vulkan-hpp.lua) |
-| 外部构建系统(`install()`) | [`compat.openssl`](pkgs/c/compat.openssl.lua) |
+| 外部构建系统(`install()`) | [`compat.openssl`](pkgs/c/compat.openssl.lua) · [`compat.openmp`](pkgs/c/compat.openmp.lua) |
 
 其余形态,以及每个描述符为何这样写,见 **[描述符示例总览(按形态)](docs/zh/descriptor-examples.md)**。
 

mcpp.toml

@@ -82,6 +82,7 @@ members = [
     "tests/examples/mysql-connector-cpp",
     "tests/examples/nlohmann.json",
     "tests/examples/openblas",
+    "tests/examples/openmp",
     "tests/examples/openssl",
     "tests/examples/recastnavigation",
     "tests/examples/recastnavigation-features",

pkgs/c/compat.openmp.lua

@@ -0,0 +1,150 @@
+-- LLVM OpenMP runtime built from its pinned release sources.
+-- libomp implements the Clang and (on Unix) GCC OpenMP ABIs. Consumers enable
+-- OpenMP compilation themselves; this package supplies the header and runtime.
+-- Unix uses a static C-ABI runtime; Windows ships the upstream DLL/import lib.
+package = {
+    spec = "1",
+    namespace = "compat",
+    name = "openmp",
+    description = "LLVM OpenMP runtime and omp.h, built from source",
+    licenses = {"Apache-2.0 WITH LLVM-exception"},
+    repo = "https://github.com/llvm/llvm-project/tree/main/openmp",
+    type = "package",
+    xpm = {
+        linux = {
+            deps = { "xim:cmake@latest", "xim:python@3.13.12" },
+            ["22.1.8"] = {
+                url = "https://github.com/llvm/llvm-project/releases/download/llvmorg-22.1.8/llvm-project-22.1.8.src.tar.xz",
+                sha256 = "922f1817a0df7b1489272d18134ee0087a8b068828f87ac63b9861b1a9965888",
+            },
+        },
+        macosx = {
+            deps = { "xim:cmake@latest", "xim:python@3.13.12" },
+            ["22.1.8"] = {
+                url = "https://github.com/llvm/llvm-project/releases/download/llvmorg-22.1.8/llvm-project-22.1.8.src.tar.xz",
+                sha256 = "922f1817a0df7b1489272d18134ee0087a8b068828f87ac63b9861b1a9965888",
+            },
+        },
+        windows = {
+            deps = { "xim:cmake@latest", "xim:python@3.13.12" },
+            ["22.1.8"] = {
+                url = "https://github.com/llvm/llvm-project/releases/download/llvmorg-22.1.8/llvm-project-22.1.8.src.tar.xz",
+                sha256 = "922f1817a0df7b1489272d18134ee0087a8b068828f87ac63b9861b1a9965888",
+            },
+        },
+    },
+    mcpp = {
+        language = "c++23",
+        import_std = false,
+        c_standard = "c11",
+        include_dirs = {"mcpp_openmp/include"},
+        -- Written last by install(), after CMake has installed the runtime.
+        sources = {"mcpp_openmp_anchor.c"},
+        targets = {["openmp"] = {kind = "lib"}},
+        linux = {ldflags = {"-Lmcpp_openmp/lib", "-lomp", "-lpthread", "-ldl"}},
+        macosx = {ldflags = {"-Lmcpp_openmp/lib", "-lomp"}},
+        windows = {
+            ldflags = {"-Lmcpp_openmp/lib", "-llibomp"},
+            runtime = {library_dirs = {"mcpp_openmp/bin"}},
+        },
+        deps = {},
+    },
+}
+
+import("xim.libxpkg.pkginfo")
+import("xim.libxpkg.log")
+
+local function quote(value)
+    value = tostring(value)
+    if os.host() == "windows" then
+        return '"' .. value:gsub('"', '\\"') .. '"'
+    end
+    return "'" .. value:gsub("'", "'\\''") .. "'"
+end
+
+local function tool(dep, name)
+    local info = pkginfo.build_dep(dep)
+    if info then
+        for _, candidate in ipairs({
+            path.join(info.bin or info.path or "", name),
+            path.join(info.path or "", "CMake.app", "Contents", "bin", name),
+        }) do
+            if os.isfile(candidate) then return candidate end
+        end
+    end
+    return name
+end
+
+local function run(command, logfile)
+    command = command .. " >> " .. quote(logfile) .. " 2>&1"
+    if os.host() == "windows" then
+        -- xlings cannot reliably invoke a quoted .exe directly on Windows.
+        -- A batch file preserves CMake's arguments and reports its exit code.
+        local bat = path.join(pkginfo.install_dir(), "mcpp_openmp_run.bat")
+        io.writefile(bat, "@echo off\r\n" .. command
+            .. "\r\nif errorlevel 1 exit /b 1\r\nexit /b 0\r\n")
+        command = "cmd /c " .. quote(bat)
+    end
+    local ok, result = pcall(os.exec, command)
+    if ok and result then return true end
+    local lines = {}
+    if os.isfile(logfile) then
+        for line in (io.readfile(logfile) .. "\n"):gmatch("(.-)\n") do
+            lines[#lines + 1] = line
+        end
+    end
+    local tail = table.concat(lines, "\n", math.max(1, #lines - 59), #lines)
+    log.error("compat.openmp: CMake failed; see %s\n%s", logfile, tail)
+    return false
+end
+
+function install()
+    local prefix = pkginfo.install_dir()
+    local root = "llvm-project-" .. pkginfo.version() .. ".src"
+    if not os.isdir(root) then
+        log.error("compat.openmp: missing extracted source %s", root)
+        return false
+    end
+    os.tryrm(prefix)
+    os.mv(root, prefix)
+    local build = path.join(prefix, "mcpp_openmp_build")
+    local output = path.join(prefix, "mcpp_openmp")
+    local logfile = path.join(prefix, "mcpp_openmp_build.log")
+    local windows = os.host() == "windows"
+    local cmake = tool("xim:cmake", windows and "cmake.exe" or "cmake")
+    local python = tool("xim:python", windows and "python.exe" or "python3")
+    local options = windows and ' -G "Visual Studio 17 2022" -A x64 -DLIBOMP_ENABLE_SHARED=ON'
+                             or ' -G "Unix Makefiles" -DLIBOMP_ENABLE_SHARED=OFF'
+    if not windows then
+        -- install() runs before consumer toolchain resolution. Build the C-ABI
+        -- runtime with the system SDK; libomp has no C++ standard-library ABI.
+        options = options .. " -DCMAKE_C_COMPILER=/usr/bin/cc -DCMAKE_CXX_COMPILER=/usr/bin/c++"
+            .. " -DCMAKE_ASM_COMPILER=/usr/bin/cc -DCMAKE_MAKE_PROGRAM=/usr/bin/make"
+    end
+    local configure = quote(cmake) .. " -S " .. quote(path.join(prefix, "openmp"))
+        .. " -B " .. quote(build) .. " -DCMAKE_BUILD_TYPE=Release"
+        .. " -DCMAKE_INSTALL_PREFIX=" .. quote(output)
+        .. " -DPython3_EXECUTABLE=" .. quote(python)
+        .. " -DOPENMP_ENABLE_LIBOMPTARGET=OFF -DOPENMP_ENABLE_OMPT_TOOLS=OFF"
+        .. " -DLIBOMP_OMPT_SUPPORT=OFF -DLIBOMP_USE_ITT_NOTIFY=OFF" .. options
+    if not run(configure, logfile) then return false end
+    if not run(quote(cmake) .. " --build " .. quote(build) .. " --config Release --parallel 4", logfile) then return false end
+    if windows then
+        -- The Visual Studio generator can omit the archive of upstream's
+        -- source-less ompimp target. The DLL link already produced an import
+        -- library for these exact exports; give install() its expected name.
+        local expected = path.join(build, "runtime", "src", "Release", "libomp.lib")
+        local linked = path.join(build, "runtime", "src", "Release", "libomp.dll.lib")
+        if not os.isfile(expected) and os.isfile(linked) then
+            os.cp(linked, expected)
+        end
+    end
+    if not run(quote(cmake) .. " --install " .. quote(build) .. " --config Release", logfile) then return false end
+    local library = path.join(output, "lib", windows and "libomp.lib" or "libomp.a")
+    if not os.isfile(library) or not os.isfile(path.join(output, "include", "omp.h")) then
+        log.error("compat.openmp: missing installed header/library; see %s", logfile)
+        return false
+    end
+    io.writefile(path.join(prefix, "mcpp_openmp_anchor.c"), "int mcpp_compat_openmp_anchor(void) { return 0; }\n")
+    return true
+end

tests/examples/openmp/mcpp.toml

@@ -0,0 +1,20 @@
+# OpenMP consumer test: the package supplies the compiler-facing omp.h entry
+# point, while this member enables the selected compiler's OpenMP runtime.
+[package]
+name = "openmp-tests"
+version = "0.1.0"
+
+[dependencies.compat]
+openmp = "22.1.8"
+
+[target.'cfg(linux)'.build]
+cxxflags = ["-fopenmp"]
+
+[target.'cfg(macos)'.build]
+cxxflags = ["-Xclang", "-fopenmp"]
+
+[target.'cfg(windows)'.build]
+cxxflags = ["-fopenmp"]
+
+[indices]
+compat = { path = "../../.." }

tests/examples/openmp/tests/openmp.cpp

@@ -0,0 +1,18 @@
+#include <omp.h>
+
+#ifndef _OPENMP
+#error "The compiler must enable OpenMP; a header cannot supply _OPENMP."
+#endif
+
+int main() {
+    omp_set_dynamic(0);
+    int sum = 0;
+    int threads = 0;
+#pragma omp parallel num_threads(2) reduction(+:sum)
+    {
+#pragma omp single
+        threads = omp_get_num_threads();
+        sum += omp_get_thread_num() + 1;
+    }
+    return threads == 2 && sum == 3 ? 0 : 1;
+}