macOS: queue for munmap operations

Makefile

@@ -1654,6 +1654,7 @@ ifeq ($(uname_S),Darwin)
 		COMPAT_CFLAGS += -DAPPLE_COMMON_CRYPTO
         endif
 	PTHREAD_LIBS =
+	COMPAT_OBJS += compat/osxmmap.o
 endif
 
 ifdef NO_LIBGEN_H

compat/osxmmap.c

@@ -0,0 +1,49 @@
+#include <pthread.h>
+#include "../git-compat-util.h"
+/* We need original mmap/munmap here. */
+#undef mmap
+#undef munmap
+
+/*
+ * OSX doesn't have any specific setting like Linux's vm.max_map_count,
+ * so COUNT_MAX can be any large number. We here set it to the default
+ * value of Linux's vm.max_map_count.
+ */
+#define COUNT_MAX (65530)
+
+struct munmap_queue {
+	void *start;
+	size_t length;
+};
+
+void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset)
+{
+	/*
+	 * We can simply discard munmap operations in the queue by
+	 * restricting mmap arguments.
+	 */
+	if (start != NULL || flags != MAP_PRIVATE || prot != PROT_READ)
+		die("invalid usage of mmap");
+	return mmap(start, length, prot, flags, fd, offset);
+}
+
+int git_munmap(void *start, size_t length)
+{
+	static pthread_mutex_t mutex;
+	static struct munmap_queue *queue;
+	static int count;
+	int i;
+
+	pthread_mutex_lock(&mutex);
+	if (!queue)
+		queue = xmalloc(COUNT_MAX * sizeof(struct munmap_queue));
+	queue[count].start = start;
+	queue[count].length = length;
+	if (++count == COUNT_MAX) {
+		for (i = 0; i < COUNT_MAX; i++)
+			munmap(queue[i].start, queue[i].length);
+		count = 0;
+	}
+	pthread_mutex_unlock(&mutex);
+	return 0;
+}

compat/posix.h

@@ -278,6 +278,13 @@ int git_munmap(void *start, size_t length);
 
 #include <sys/mman.h>
 
+#if defined(__APPLE__)
+#define mmap git_mmap
+#define munmap git_munmap
+void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset);
+int git_munmap(void *start, size_t length);
+#endif
+
 #endif /* NO_MMAP || USE_WIN32_MMAP */
 
 #ifndef MAP_FAILED

contrib/buildsystems/CMakeLists.txt

@@ -271,6 +271,10 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
 		compat/strdup.c)
 	set(NO_UNIX_SOCKETS 1)
 
+elseif(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
+	list(APPEND compat_SOURCES
+		compat/osxmmap.c)
+
 elseif(CMAKE_SYSTEM_NAME STREQUAL "Linux")
 	add_compile_definitions(PROCFS_EXECUTABLE_PATH="/proc/self/exe" HAVE_DEV_TTY )
 	list(APPEND compat_SOURCES unix-socket.c unix-stream-server.c compat/linux/procinfo.c)

meson.build

@@ -1275,6 +1275,8 @@ elif host_machine.system() == 'windows'
   else
     libgit_sources += 'compat/mingw.c'
   endif
+elif host_machine.system() == 'darwin'
+  libgit_sources += 'compat/osxmmap.c'
 endif
 
 if host_machine.system() == 'linux'