[PATCH v3] Handle atexit list internaly for unthreaded builds

[Etienne Buira <etienne.buira@gmail.com>]

Wrap atexit()s calls on unthreaded builds to handle callback list
internally.

This is needed because on unthreaded builds, asyncs inherits parent's
atexit() list, that gets run as soon as the async exit()s (and again at
the end of the parent process). That led to remove temporary and lock
files too early.

Fixes test 5537 (temporary shallow file vanished before unpack-objects
could open it)

V2: remove an obvious mistake
V3: wrap, rename and add define in git-compat-util.h

Thanks-to: Duy Nguyen <pclouds@gmail.com>
Signed-off-by: Etienne Buira <etienne.buira@gmail.com>
---
 builtin/clone.c   |  5 -----
 git-compat-util.h |  5 +++++
 run-command.c     | 42 ++++++++++++++++++++++++++++++++++++++++++
 shallow.c         |  7 ++-----
 4 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/builtin/clone.c b/builtin/clone.c
index bbd169c..e122f33 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -390,7 +390,6 @@ static void clone_local(const char *src_repo, const char *dest_repo)
 
 static const char *junk_work_tree;
 static const char *junk_git_dir;
-static pid_t junk_pid;
 static enum {
 	JUNK_LEAVE_NONE,
 	JUNK_LEAVE_REPO,
@@ -417,8 +416,6 @@ static void remove_junk(void)
 		break;
 	}
 
-	if (getpid() != junk_pid)
-		return;
 	if (junk_git_dir) {
 		strbuf_addstr(&sb, junk_git_dir);
 		remove_dir_recursively(&sb, 0);
@@ -758,8 +755,6 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	struct refspec *refspec;
 	const char *fetch_pattern;
 
-	junk_pid = getpid();
-
 	packet_trace_identity("clone");
 	argc = parse_options(argc, argv, prefix, builtin_clone_options,
 			     builtin_clone_usage, 0);
diff --git a/git-compat-util.h b/git-compat-util.h
index f587749..6dd63dd 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -577,6 +577,11 @@ int inet_pton(int af, const char *src, void *dst);
 const char *inet_ntop(int af, const void *src, char *dst, size_t size);
 #endif
 
+#ifdef NO_PTHREADS
+#define atexit git_atexit
+extern int git_atexit(void (*handler)(void));
+#endif
+
 extern void release_pack_memory(size_t);
 
 typedef void (*try_to_free_t)(size_t);
diff --git a/run-command.c b/run-command.c
index 35a3ebf..f8dc969 100644
--- a/run-command.c
+++ b/run-command.c
@@ -624,6 +624,47 @@ static int async_die_is_recursing(void)
 	return ret != NULL;
 }
 
+#else
+
+static struct {
+	void (**handlers)(void);
+	size_t nr;
+	size_t alloc;
+} git_atexit_hdlrs;
+
+static int git_atexit_installed;
+
+static void git_atexit_dispatch()
+{
+	size_t i;
+
+	for (i=git_atexit_hdlrs.nr ; i ; i--)
+		git_atexit_hdlrs.handlers[i-1]();
+}
+
+static void git_atexit_clear()
+{
+	free(git_atexit_hdlrs.handlers);
+	memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
+	git_atexit_installed = 0;
+}
+
+#define tmp_atexit atexit
+#undef atexit
+int git_atexit(void (*handler)(void))
+{
+	ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
+	git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
+	if (!git_atexit_installed) {
+		if (atexit(&git_atexit_dispatch))
+			return -1;
+		git_atexit_installed = 1;
+	}
+	return 0;
+}
+#define atexit tmp_atexit
+#undef tmp_atexit
+
 #endif
 
 int start_async(struct async *async)
@@ -682,6 +723,7 @@ int start_async(struct async *async)
 			close(fdin[1]);
 		if (need_out)
 			close(fdout[0]);
+		git_atexit_clear();
 		exit(!!async->proc(proc_in, proc_out, async->data));
 	}
 
diff --git a/shallow.c b/shallow.c
index de07709..f067811 100644
--- a/shallow.c
+++ b/shallow.c
@@ -226,7 +226,6 @@ static void remove_temporary_shallow_on_signal(int signo)
 
 const char *setup_temporary_shallow(const struct sha1_array *extra)
 {
-	static int installed_handler;
 	struct strbuf sb = STRBUF_INIT;
 	int fd;
 
@@ -237,10 +236,8 @@ const char *setup_temporary_shallow(const struct sha1_array *extra)
 		strbuf_addstr(&temporary_shallow, git_path("shallow_XXXXXX"));
 		fd = xmkstemp(temporary_shallow.buf);
 
-		if (!installed_handler) {
-			atexit(remove_temporary_shallow);
-			sigchain_push_common(remove_temporary_shallow_on_signal);
-		}
+		atexit(remove_temporary_shallow);
+		sigchain_push_common(remove_temporary_shallow_on_signal);
 
 		if (write_in_full(fd, sb.buf, sb.len) != sb.len)
 			die_errno("failed to write to %s",
-- 
2.0.4