run-command: introduce child_process_init()

Add a helper function for initializing those struct child_process
variables for which the macro CHILD_PROCESS_INIT can't be used.

Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/technical/api-run-command.txt

@@ -13,6 +13,10 @@ produces in the caller in order to process it.
 Functions
 ---------
 
+`child_process_init`
+
+	Initialize a struct child_process variable.
+
 `start_command`::
 
 	Start a sub-process. Takes a pointer to a `struct child_process`
@@ -96,8 +100,8 @@ command to run in a sub-process.
 
 The caller:
 
-1. allocates and clears (memset(&chld, 0, sizeof(chld)); or
-   using CHILD_PROCESS_INIT) a struct child_process variable;
+1. allocates and clears (using child_process_init() or
+   CHILD_PROCESS_INIT) a struct child_process variable;
 2. initializes the members;
 3. calls start_command();
 4. processes the data;

connect.c

@@ -537,7 +537,8 @@ static struct child_process *git_proxy_connect(int fd[2], char *host)
 
 	get_host_and_port(&host, &port);
 
-	proxy = xcalloc(1, sizeof(*proxy));
+	proxy = xmalloc(sizeof(*proxy));
+	child_process_init(proxy);
 	argv_array_push(&proxy->args, git_proxy_command);
 	argv_array_push(&proxy->args, host);
 	argv_array_push(&proxy->args, port);
@@ -694,7 +695,8 @@ struct child_process *git_connect(int fd[2], const char *url,
 			     target_host, 0);
 		free(target_host);
 	} else {
-		conn = xcalloc(1, sizeof(*conn));
+		conn = xmalloc(sizeof(*conn));
+		child_process_init(conn);
 
 		strbuf_addstr(&cmd, prog);
 		strbuf_addch(&cmd, ' ');

run-command.c

@@ -8,6 +8,12 @@
 # define SHELL_PATH "/bin/sh"
 #endif
 
+void child_process_init(struct child_process *child)
+{
+	memset(child, 0, sizeof(*child));
+	argv_array_init(&child->args);
+}
+
 struct child_to_clean {
 	pid_t pid;
 	struct child_to_clean *next;

run-command.h

@@ -45,6 +45,7 @@ struct child_process {
 };
 
 #define CHILD_PROCESS_INIT { NULL, ARGV_ARRAY_INIT }
+void child_process_init(struct child_process *);
 
 int start_command(struct child_process *);
 int finish_command(struct child_process *);

transport-helper.c

@@ -118,7 +118,8 @@ static struct child_process *get_helper(struct transport *transport)
 	if (data->helper)
 		return data->helper;
 
-	helper = xcalloc(1, sizeof(*helper));
+	helper = xmalloc(sizeof(*helper));
+	child_process_init(helper);
 	helper->in = -1;
 	helper->out = -1;
 	helper->err = 0;
@@ -395,7 +396,7 @@ static int get_importer(struct transport *transport, struct child_process *fasti
 	struct child_process *helper = get_helper(transport);
 	struct helper_data *data = transport->data;
 	int cat_blob_fd, code;
-	memset(fastimport, 0, sizeof(*fastimport));
+	child_process_init(fastimport);
 	fastimport->in = helper->out;
 	argv_array_push(&fastimport->args, "fast-import");
 	argv_array_push(&fastimport->args, debug ? "--stats" : "--quiet");