Merge pull request #61 from kiplingw/kip-pkg-config

Add support for pkg-config (#60)

3 files changed, 128 insertions, 2 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index e2d7d53..845ec28 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,7 +1,10 @@
 CMAKE_MINIMUM_REQUIRED(VERSION 3.5 FATAL_ERROR)
 
-# ---[ Project and semantic versioning.
-PROJECT(cpuinfo C CXX)
+# ---[ Setup project
+PROJECT(
+    cpuinfo
+    LANGUAGES C CXX
+    HOMEPAGE_URL https://github.com/pytorch/cpuinfo)
 
 # ---[ Options.
 SET(CPUINFO_LIBRARY_TYPE "default" CACHE STRING "Type of cpuinfo library (shared, static, or default) to build")
@@ -14,6 +17,7 @@ OPTION(CPUINFO_BUILD_TOOLS "Build command-line tools" ON)
 OPTION(CPUINFO_BUILD_UNIT_TESTS "Build cpuinfo unit tests" ON)
 OPTION(CPUINFO_BUILD_MOCK_TESTS "Build cpuinfo mock tests" ON)
 OPTION(CPUINFO_BUILD_BENCHMARKS "Build cpuinfo micro-benchmarks" ON)
+OPTION(CPUINFO_BUILD_PKG_CONFIG "Build pkg-config manifest" ON)
 
 # ---[ CMake options
 INCLUDE(GNUInstallDirs)
@@ -821,3 +825,34 @@ IF(CPUINFO_SUPPORTED_PLATFORM AND CPUINFO_BUILD_TOOLS)
     INSTALL(TARGETS cpuid-dump RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
   ENDIF()
 ENDIF()
+
+# ---[ pkg-config manifest. This is mostly from JsonCpp...
+IF(CPUINFO_BUILD_PKG_CONFIG)
+
+  FUNCTION(JOIN_PATHS joined_path first_path_segment)
+    SET(temp_path "${first_path_segment}")
+    FOREACH(current_segment IN LISTS ARGN)
+      IF(NOT ("${current_segment}" STREQUAL ""))
+        IF(IS_ABSOLUTE "${current_segment}")
+          SET(temp_path "${current_segment}")
+        ELSE()
+          SET(temp_path "${temp_path}/${current_segment}")
+        ENDIF()
+      ENDIF()
+    ENDFOREACH()
+    SET(${joined_path} "${temp_path}" PARENT_SCOPE)
+  ENDFUNCTION()
+
+  JOIN_PATHS(libdir_for_pc_file "\${exec_prefix}" "${CMAKE_INSTALL_LIBDIR}")
+  JOIN_PATHS(includedir_for_pc_file "\${prefix}" "${CMAKE_INSTALL_INCLUDEDIR}")
+
+  CONFIGURE_FILE(
+    "libcpuinfo.pc.in"
+    "libcpuinfo.pc"
+    @ONLY)
+
+  INSTALL(FILES "${CMAKE_CURRENT_BINARY_DIR}/libcpuinfo.pc"
+  DESTINATION "${CMAKE_INSTALL_LIBDIR}/pkgconfig")
+
+ENDIF()
+
diff --git a/README.md b/README.md
index 97e65cd..0eb71a5 100644
--- a/README.md
+++ b/README.md
@@ -100,6 +100,84 @@ for (uint32_t i = 0; i < current_l2->processor_count; i++) {
 pthread_setaffinity_np(pthread_self(), sizeof(cpu_set_t), &cpu_set);
 ```
 
+## Use via pkg-config
+
+If you would like to provide your project's build environment with the necessary compiler and linker flags in a portable manner, the library by default when built enables `CPUINFO_BUILD_PKG_CONFIG` and will generate a [pkg-config](https://www.freedesktop.org/wiki/Software/pkg-config/) manifest (_libcpuinfo.pc_). Here are several examples of how to use it:
+
+### Command Line
+
+If you used your distro's package manager to install the library, you can verify that it is available to your build environment like so:
+
+```console
+$ pkg-config --cflags --libs libcpuinfo
+-I/usr/include/x86_64-linux-gnu/ -L/lib/x86_64-linux-gnu/ -lcpuinfo
+```
+
+If you have installed the library from source into a non-standard prefix, pkg-config may need help finding it:
+
+```console
+$ PKG_CONFIG_PATH="/home/me/projects/cpuinfo/prefix/lib/pkgconfig/:$PKG_CONFIG_PATH" pkg-config --cflags --libs libcpuinfo
+-I/home/me/projects/cpuinfo/prefix/include -L/home/me/projects/cpuinfo/prefix/lib -lcpuinfo
+```
+
+### GNU Autotools
+
+To [use](https://autotools.io/pkgconfig/pkg_check_modules.html) with the GNU Autotools include the following snippet in your project's `configure.ac`:
+
+```makefile
+# CPU INFOrmation library...
+PKG_CHECK_MODULES(
+    [libcpuinfo], [libcpuinfo], [],
+    [AC_MSG_ERROR([libcpuinfo missing...])])
+YOURPROJECT_CXXFLAGS="$YOURPROJECT_CXXFLAGS $libcpuinfo_CFLAGS"
+YOURPROJECT_LIBS="$YOURPROJECT_LIBS $libcpuinfo_LIBS"
+```
+
+### Meson
+
+To use with Meson you just need to add `dependency('libcpuinfo')` as a dependency for your executable.
+
+```meson
+project(
+    'MyCpuInfoProject',
+    'cpp',
+    meson_version: '>=0.55.0'
+)
+
+executable(
+    'MyCpuInfoExecutable',
+    sources: 'main.cpp',
+    dependencies: dependency('libcpuinfo')
+)
+```
+
+### CMake
+
+To use with CMake use the [FindPkgConfig](https://cmake.org/cmake/help/latest/module/FindPkgConfig.html) module. Here is an example:
+
+```cmake
+cmake_minimum_required(VERSION 3.6)
+project("MyCpuInfoProject")
+
+find_package(PkgConfig)
+pkg_check_modules(CpuInfo REQUIRED IMPORTED_TARGET libcpuinfo)
+
+add_executable(${PROJECT_NAME} main.cpp)
+target_link_libraries(${PROJECT_NAME} PkgConfig::CpuInfo)
+```
+
+### Makefile
+
+To use within a vanilla makefile, you can call pkg-config directly to supply compiler and linker flags using shell substitution.
+
+```makefile
+CFLAGS=-g3 -Wall -Wextra -Werror ...
+LDFLAGS=-lfoo ...
+...
+CFLAGS+= $(pkg-config --cflags libcpuinfo)
+LDFLAGS+= $(pkg-config --libs libcpuinfo)
+```
+
 ## Exposed information
 - [x] Processor (SoC) name
 - [x] Microarchitecture
@@ -202,3 +280,4 @@ pthread_setaffinity_np(pthread_self(), sizeof(cpu_set_t), &cpu_set);
   - [x] Using `GetLogicalProcessorInformationEx` (Windows)
   - [x] Using sysfs (Linux)
   - [x] Using chipset name (ARM/Linux)
+
diff --git a/libcpuinfo.pc.in b/libcpuinfo.pc.in
new file mode 100644
index 0000000..3027da3
--- /dev/null
+++ b/libcpuinfo.pc.in
@@ -0,0 +1,12 @@
+prefix=@CMAKE_INSTALL_PREFIX@
+exec_prefix=@CMAKE_INSTALL_PREFIX@
+libdir=@libdir_for_pc_file@
+includedir=@includedir_for_pc_file@
+
+Name: lib@CMAKE_PROJECT_NAME@
+Description: Library to detect essential performance optimization information about host CPU.
+Version: 
+URL: @PROJECT_HOMEPAGE_URL@
+Libs: -L${libdir} -lcpuinfo
+Cflags: -I${includedir}
+