From 8c41e7f62e6ac81101335ca7b96fb8a7ec7792d3 Mon Sep 17 00:00:00 2001
From: Martijn van Beurden <mvanb1@gmail.com>
Date: Tue, 1 Aug 2023 09:04:16 +0200
Subject: [PATCH] Add multithreading to CMake

---
 CMakeLists.txt             | 11 +++++++++++
 config.cmake.h.in          |  3 +++
 src/libFLAC/CMakeLists.txt |  4 ++++
 3 files changed, 18 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index fb23b7d9..a81ff6f6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -24,6 +24,7 @@ option(INSTALL_PKGCONFIG_MODULES "Install PkgConfig modules" ON)
 option(INSTALL_CMAKE_CONFIG_MODULE "Install CMake package-config module" ON)
 option(WITH_OGG "ogg support (default: test for libogg)" ON)
 option(BUILD_SHARED_LIBS "Build shared instead of static libraries" OFF)
+option(ENABLE_MULTITHREADING "Enable multithreading if pthreads is available" ON)
 
 set(VERSION ${PROJECT_VERSION})
 
@@ -113,6 +114,7 @@ check_include_file("inttypes.h" HAVE_INTTYPES_H)
 check_include_file("stdint.h" HAVE_STDINT_H)
 check_include_file("stdbool.h" HAVE_STDBOOL_H)
 check_include_file("arm_neon.h" FLAC__HAS_NEONINTRIN)
+check_include_file("semaphore.h" HAVE_SEMAPHORE_H)
 
 if(NOT HAVE_STDINT_H OR NOT HAVE_STDBOOL_H)
     message(SEND_ERROR "Header stdint.h and/or stdbool.h not found")
@@ -198,6 +200,15 @@ if(CMAKE_BUILD_TYPE STREQUAL Debug OR CMAKE_BUILD_TYPE STREQUAL RelWithDebInfo)
     add_definitions(-DFLAC__OVERFLOW_DETECT)
 endif()
 
+if(ENABLE_MULTITHREADING AND HAVE_SEMAPHORE_H)
+    set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
+    set(THREADS_PREFER_PTHREAD_FLAG TRUE)
+    find_package(Threads)
+    if(CMAKE_USE_PTHREADS_INIT)
+        set(HAVE_PTHREAD 1)
+    endif()
+endif()
+
 add_subdirectory("src")
 add_subdirectory("microbench")
 if(BUILD_DOCS)
diff --git a/config.cmake.h.in b/config.cmake.h.in
index acc73f08..1aeaffc8 100644
--- a/config.cmake.h.in
+++ b/config.cmake.h.in
@@ -88,6 +88,9 @@
 /* Define to 1 if you have the <memory.h> header file. */
 #cmakedefine HAVE_MEMORY_H
 
+/* Define if multithreading is enabled */
+#cmakedefine HAVE_PTHREAD 1
+
 /* Define to 1 if you have the <stdint.h> header file. */
 #cmakedefine HAVE_STDINT_H
 
diff --git a/src/libFLAC/CMakeLists.txt b/src/libFLAC/CMakeLists.txt
index cf7368f6..6319da6f 100644
--- a/src/libFLAC/CMakeLists.txt
+++ b/src/libFLAC/CMakeLists.txt
@@ -108,6 +108,10 @@ else()
     endif()
 endif()
 
+if(HAVE_PTHREAD)
+    target_link_libraries(FLAC PUBLIC Threads::Threads)
+endif()
+
 add_library(FLAC::FLAC ALIAS FLAC)
 
 install(TARGETS FLAC EXPORT targets