Enable threaded async procedures whenever pthreads is available

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/technical/api-run-command.txt

@@ -231,8 +231,9 @@ The function pointer in .proc has the following signature:
 
 
 There are serious restrictions on what the asynchronous function can do
-because this facility is implemented by a pipe to a forked process on
-UNIX, but by a thread in the same address space on Windows:
+because this facility is implemented by a thread in the same address
+space on most platforms (when pthreads is available), but by a pipe to
+a forked process otherwise:
 
 . It cannot change the program's state (global variables, environment,
   etc.) in a way that the caller notices; in other words, .in and .out

Makefile

@@ -979,7 +979,6 @@ ifeq ($(uname_S),Windows)
 	NO_CURL = YesPlease
 	NO_PYTHON = YesPlease
 	BLK_SHA1 = YesPlease
-	ASYNC_AS_THREAD = YesPlease
 
 	CC = compat/vcbuild/scripts/clink.pl
 	AR = compat/vcbuild/scripts/lib.pl
@@ -1031,7 +1030,6 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	NO_REGEX = YesPlease
 	NO_PYTHON = YesPlease
 	BLK_SHA1 = YesPlease
-	ASYNC_AS_THREAD = YesPlease
 	COMPAT_CFLAGS += -D__USE_MINGW_ACCESS -DNOGDI -Icompat -Icompat/fnmatch -Icompat/win32
 	COMPAT_CFLAGS += -DSTRIP_EXTENSION=\".exe\"
 	COMPAT_OBJS += compat/mingw.o compat/fnmatch/fnmatch.o compat/winansi.o \
@@ -1344,9 +1342,6 @@ ifdef NO_PTHREADS
 else
 	EXTLIBS += $(PTHREAD_LIBS)
 	LIB_OBJS += thread-utils.o
-ifdef ASYNC_AS_THREAD
-	BASIC_CFLAGS += -DASYNC_AS_THREAD
-endif
 endif
 
 ifdef DIR_HAS_BSD_GROUP_SEMANTICS

run-command.c

@@ -447,18 +447,18 @@ int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const
 	return run_command(&cmd);
 }
 
-#ifdef ASYNC_AS_THREAD
+#ifndef NO_PTHREADS
 static pthread_t main_thread;
 static int main_thread_set;
 static pthread_key_t async_key;
 
 static void *run_thread(void *data)
 {
 	struct async *async = data;
+	intptr_t ret;
 
 	pthread_setspecific(async_key, async);
-
-	intptr_t ret = async->proc(async->proc_in, async->proc_out, async->data);
+	ret = async->proc(async->proc_in, async->proc_out, async->data);
 	return (void *)ret;
 }
 
@@ -521,7 +521,7 @@ int start_async(struct async *async)
 	else
 		proc_out = -1;
 
-#ifndef ASYNC_AS_THREAD
+#ifdef NO_PTHREADS
 	/* Flush stdio before fork() to avoid cloning buffers */
 	fflush(NULL);
 
@@ -590,7 +590,7 @@ int start_async(struct async *async)
 
 int finish_async(struct async *async)
 {
-#ifndef ASYNC_AS_THREAD
+#ifdef NO_PTHREADS
 	return wait_or_whine(async->pid, "child process", 0);
 #else
 	void *ret = (void *)(intptr_t)(-1);

run-command.h

@@ -1,7 +1,7 @@
 #ifndef RUN_COMMAND_H
 #define RUN_COMMAND_H
 
-#ifdef ASYNC_AS_THREAD
+#ifndef NO_PTHREADS
 #include <pthread.h>
 #endif
 
@@ -78,7 +78,7 @@ struct async {
 	void *data;
 	int in;		/* caller writes here and closes it */
 	int out;	/* caller reads from here and closes it */
-#ifndef ASYNC_AS_THREAD
+#ifdef NO_PTHREADS
 	pid_t pid;
 #else
 	pthread_t tid;