hook: add internal state alloc/free callbacks

Some hooks use opaque structs to keep internal state between callbacks.

Because hooks ran sequentially (jobs == 1) with one command per hook,
these internal states could be allocated on the stack for each hook run.

Next commits add the ability to run multiple commands for each hook, so
the states cannot be shared or stored on the stack anymore, especially
since down the line we will also enable parallel execution (jobs > 1).

Add alloc/free helpers for each hook, doing a "deep" alloc/init & free
of their internal opaque struct.

The alloc callback takes a context pointer, to initialize the struct at
at the time of resource acquisition.

These callbacks must always be provided together: no alloc without free
and no free without alloc, otherwise a BUG() is triggered.

Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 26 insertions, 7 deletions

diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index b5379a4895..5259f09788 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -901,6 +901,26 @@ static int feed_receive_hook_cb(int hook_stdin_fd, void *pp_cb UNUSED, void *pp_
 	return state->cmd ? 0 : 1;  /* 0 = more to come, 1 = EOF */
 }
 
+static void *receive_hook_feed_state_alloc(void *feed_pipe_ctx)
+{
+	struct receive_hook_feed_state *init_state = feed_pipe_ctx;
+	struct receive_hook_feed_state *data = xcalloc(1, sizeof(*data));
+	data->report = init_state->report;
+	data->cmd = init_state->cmd;
+	data->skip_broken = init_state->skip_broken;
+	strbuf_init(&data->buf, 0);
+	return data;
+}
+
+static void receive_hook_feed_state_free(void *data)
+{
+	struct receive_hook_feed_state *d = data;
+	if (!d)
+		return;
+	strbuf_release(&d->buf);
+	free(d);
+}
+
 static int run_receive_hook(struct command *commands,
 			    const char *hook_name,
 			    int skip_broken,
@@ -908,7 +928,7 @@ static int run_receive_hook(struct command *commands,
 {
 	struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT;
 	struct command *iter = commands;
-	struct receive_hook_feed_state feed_state;
+	struct receive_hook_feed_state feed_init_state = { 0 };
 	struct async sideband_async;
 	int sideband_async_started = 0;
 	int saved_stderr = -1;
@@ -938,16 +958,15 @@ static int run_receive_hook(struct command *commands,
 	prepare_sideband_async(&sideband_async, &saved_stderr, &sideband_async_started);
 
 	/* set up stdin callback */
-	feed_state.cmd = commands;
-	feed_state.skip_broken = skip_broken;
-	feed_state.report = NULL;
-	strbuf_init(&feed_state.buf, 0);
-	opt.feed_pipe_cb_data = &feed_state;
+	feed_init_state.cmd = commands;
+	feed_init_state.skip_broken = skip_broken;
+	opt.feed_pipe_ctx = &feed_init_state;
 	opt.feed_pipe = feed_receive_hook_cb;
+	opt.feed_pipe_cb_data_alloc = receive_hook_feed_state_alloc;
+	opt.feed_pipe_cb_data_free = receive_hook_feed_state_free;
 
 	ret = run_hooks_opt(the_repository, hook_name, &opt);
 
-	strbuf_release(&feed_state.buf);
 	finish_sideband_async(&sideband_async, saved_stderr, sideband_async_started);
 
 	return ret;