Commit c1189cae authored by Jeff King's avatar Jeff King Committed by Junio C Hamano

refactor argv_array into generic code

The submodule code recently grew generic code to build a
dynamic argv array. Many other parts of the code can reuse
this, too, so let's make it generically available.

There are two enhancements not found in the original code:

  1. We now handle the NULL-termination invariant properly,
     even when no strings have been pushed (before, you
     could have an empty, NULL argv). This was not a problem
     for the submodule code, which always pushed at least
     one argument, but was not sufficiently safe for
     generic code.

  2. There is a formatted variant of the "push" function.
     This is a convenience function which was not needed by
     the submodule code, but will make it easier to port
     other users to the new code.
Signed-off-by: 's avatarJeff King <>
Signed-off-by: 's avatarJunio C Hamano <>
parent 7878b07c
argv-array API
The argv-array API allows one to dynamically build and store
NULL-terminated lists. An argv-array maintains the invariant that the
`argv` member always points to a non-NULL array, and that the array is
always NULL-terminated at the element pointed to by `argv[argc]`. This
makes the result suitable for passing to functions expecting to receive
argv from main(), or the link:api-run-command.html[run-command API].
The link:api-string-list.html[string-list API] is similar, but cannot be
used for these purposes; instead of storing a straight string pointer,
it contains an item structure with a `util` field that is not compatible
with the traditional argv interface.
Each `argv_array` manages its own memory. Any strings pushed into the
array are duplicated, and all memory is freed by argv_array_clear().
Data Structures
`struct argv_array`::
A single array. This should be initialized by assignment from
`ARGV_ARRAY_INIT`, or by calling `argv_array_init`. The `argv`
member contains the actual array; the `argc` member contains the
number of elements in the array, not including the terminating
Initialize an array. This is no different than assigning from
Push a copy of a string onto the end of the array.
Format a string and push it onto the end of the array. This is a
convenience wrapper combining `strbuf_addf` and `argv_array_push`.
Free all memory associated with the array and return it to the
initial, empty state.
......@@ -497,6 +497,7 @@ VCSSVN_LIB=vcs-svn/lib.a
LIB_H += advice.h
LIB_H += archive.h
LIB_H += argv-array.h
LIB_H += attr.h
LIB_H += blob.h
LIB_H += builtin.h
......@@ -575,6 +576,7 @@ LIB_OBJS += alloc.o
LIB_OBJS += archive.o
LIB_OBJS += archive-tar.o
LIB_OBJS += archive-zip.o
LIB_OBJS += argv-array.o
LIB_OBJS += attr.o
LIB_OBJS += base85.o
LIB_OBJS += bisect.o
#include "cache.h"
#include "argv-array.h"
#include "strbuf.h"
static const char *empty_argv_storage = NULL;
const char **empty_argv = &empty_argv_storage;
void argv_array_init(struct argv_array *array)
array->argv = empty_argv;
array->argc = 0;
array->alloc = 0;
static void argv_array_push_nodup(struct argv_array *array, const char *value)
if (array->argv == empty_argv)
array->argv = NULL;
ALLOC_GROW(array->argv, array->argc + 2, array->alloc);
array->argv[array->argc++] = value;
array->argv[array->argc] = NULL;
void argv_array_push(struct argv_array *array, const char *value)
argv_array_push_nodup(array, xstrdup(value));
void argv_array_pushf(struct argv_array *array, const char *fmt, ...)
va_list ap;
struct strbuf v = STRBUF_INIT;
va_start(ap, fmt);
strbuf_vaddf(&v, fmt, ap);
argv_array_push_nodup(array, strbuf_detach(&v, NULL));
void argv_array_clear(struct argv_array *array)
if (array->argv != empty_argv) {
int i;
for (i = 0; i < array->argc; i++)
free((char **)array->argv[i]);
#ifndef ARGV_ARRAY_H
#define ARGV_ARRAY_H
extern const char **empty_argv;
struct argv_array {
const char **argv;
int argc;
int alloc;
#define ARGV_ARRAY_INIT { empty_argv, 0, 0 }
void argv_array_init(struct argv_array *);
void argv_array_push(struct argv_array *, const char *);
__attribute__((format (printf,2,3)))
void argv_array_pushf(struct argv_array *, const char *fmt, ...);
void argv_array_clear(struct argv_array *);
#endif /* ARGV_ARRAY_H */
......@@ -9,6 +9,7 @@
#include "refs.h"
#include "string-list.h"
#include "sha1-array.h"
#include "argv-array.h"
static struct string_list config_name_for_path;
static struct string_list config_fetch_recurse_submodules_for_name;
......@@ -388,52 +389,22 @@ void check_for_new_submodule_commits(unsigned char new_sha1[20])
sha1_array_append(&ref_tips_after_fetch, new_sha1);
struct argv_array {
const char **argv;
unsigned int argc;
unsigned int alloc;
static void init_argv(struct argv_array *array)
array->argv = NULL;
array->argc = 0;
array->alloc = 0;
static void push_argv(struct argv_array *array, const char *value)
ALLOC_GROW(array->argv, array->argc + 2, array->alloc);
array->argv[array->argc++] = xstrdup(value);
array->argv[array->argc] = NULL;
static void clear_argv(struct argv_array *array)
int i;
for (i = 0; i < array->argc; i++)
free((char **)array->argv[i]);
static void add_sha1_to_argv(const unsigned char sha1[20], void *data)
push_argv(data, sha1_to_hex(sha1));
argv_array_push(data, sha1_to_hex(sha1));
static void calculate_changed_submodule_paths(void)
struct rev_info rev;
struct commit *commit;
struct argv_array argv;
struct argv_array argv = ARGV_ARRAY_INIT;
init_revisions(&rev, NULL);
push_argv(&argv, "--"); /* argv[0] program name */
argv_array_push(&argv, "--"); /* argv[0] program name */
add_sha1_to_argv, &argv);
push_argv(&argv, "--not");
argv_array_push(&argv, "--not");
add_sha1_to_argv, &argv);
setup_revisions(argv.argc, argv.argv, &rev, NULL);
......@@ -460,7 +431,7 @@ static void calculate_changed_submodule_paths(void)
initialized_fetch_ref_tips = 0;
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