The usual pattern for an argv array is to initialize it,
push in some strings, and then clear it when done. Very
occasionally, though, we must do other exotic things with
the memory, like freeing the list but keeping the strings.
Let's provide a detach function so that callers can make use
of our API to build up the array, and then take ownership of
it.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

When we have a null-terminated array, it would be useful to convert it
or append it to an argv_array for further manipulation.

Implement argv_array_pushv() which will push a null-terminated array of
strings on to an argv_array.
Signed-off-by: NPaul Tan <pyokagan@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The argv_array_detach function (and associated free() function) was
really only useful for transferring ownership of the memory to a "struct
child_process". Now that we have an internal argv_array in that struct,
there are no callers left.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The sentinel function attribute is not understood by versions of
the gcc compiler prior to v4.0. At present, for earlier versions
of gcc, the build issues 108 warnings related to the unknown
attribute. In order to suppress the warnings, we conditionally
define the LAST_ARG_MUST_BE_NULL macro to provide the sentinel attribute
for gcc v4.0 and newer.
Signed-off-by: NRamsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

This attribute can help gcc notice when callers forget to
add a NULL sentinel to the end of the function. This is our
first use of the sentinel attribute, but we shouldn't need
to #ifdef for other compilers, as __attribute__ is already a
no-op on non-gcc-compatible compilers.
Suggested-by: NBert Wesarg <bert.wesarg@googlemail.com>
More-Spots-Found-By: NMatt Kraai <kraai@ftbfs.org>
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Allow detaching of ownership of the argv_array's contents and add a
function to free those detached argv_arrays later.

This makes it possible to use argv_array efficiently with the exiting
struct child_process which only contains a member char **argv.

Add to documentation.
Signed-off-by: NFlorian Achleitner <florian.achleitner.2.6.31@gmail.com>
Acked-by: NDavid Michael Barr <b@rr-dav.id.au>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Sometimes we build a set of similar command lines, differing
only in the final arguments (e.g., "fetch --multiple"). To
use argv_array for this, you have to either push the same
set of elements repeatedly, or break the abstraction by
manually manipulating the array's internal members.

Instead, let's provide a sanctioned "pop" function to remove
elements from the end.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

It can be convenient to push many strings in a single line
(e.g., if you are initializing an array with defaults). This
patch provides a convenience wrapper to allow this.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

An empty argv-array is initialized to point to a static
empty NULL-terminated array.  The original implementation
separates the actual storage of the NULL-terminator from the
pointer to the list.  This makes the exposed type a "const
char **", which nicely matches the type stored by the
argv-array.

However, this indirection means that one cannot use
empty_argv to initialize a static variable, since it is
not a constant.

Instead, we can expose empty_argv directly, as an array of
pointers. The only place we use it is in the ARGV_ARRAY_INIT
initializer, and it decays to a pointer appropriately there.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

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: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>