In preparation for compiling with -Wunused-parameter, we'd like to be
able to annotate some function parameters as false positives (e.g.,
parameters which must exist to conform to a callback interface).
Ideally our annotation will:
- be portable, turning into nothing on platforms which don't support
it
- be easy to read, without looking too syntactically odd or taking
attention away from the rest of the parameters
- help us notice when a parameter marked as unused is actually used,
which keeps our annotations accurate. In theory a compiler could
tell us this easily, but gcc has no such warning. Clang has
-Wused-but-marked-unused, but it triggers false positives with our
MAYBE_UNUSED annotation (e.g., for commit-slab functions)
This patch introduces an UNUSED() macro which takes the parameter name
as an argument. That lets us tweak the name in such a way that we'll
notice if somebody tries to use it. It looks like this in use:
int some_ref_cb(const char *refname,
const struct object_id *UNUSED(oid),
int UNUSED(flags),
void *UNUSED(data))
{
printf("got refname %s", refname);
return 0;
}
Because the unused parameter names are rewritten behind the scenes to
UNUSED_oid, etc, adding code like:
printf("oid is %s", oid_to_hex(oid));
will fail compilation with "oid undeclared". Sadly, the "did you mean"
feature of modern compilers is not generally smart enough to suggest the
"unused" name. If we used a very short prefix like U_oid, that does
convince gcc to say "did you mean", but since the "U_" in the suggestion
isn't much of a hint, it doesn't really help. In practice, a look at the
function definition usually makes the problem pretty obvious.
Note that we have to put the definition of UNUSED early in
git-compat-util.h, because it will eventually be used for some compat
functions themselves (both directly here and in mingw.h).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an
unusually rich command set that provides both high-level operations
and full access to internals.
Git is an Open Source project covered by the GNU General Public
License version 2 (some parts of it are under different licenses,
compatible with the GPLv2). It was originally written by Linus
Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from https://git-scm.com/
including full documentation and Git related tools.
See Documentation/gittutorial.txt to get started, then see
Documentation/giteveryday.txt for a useful minimum set of commands, and
Documentation/git-<commandname>.txt for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
CVS users may also want to read Documentation/gitcvs-migration.txt
(man gitcvs-migration or git help cvs-migration if git is
installed).
Those wishing to help with error message, usage and informational message
string translations (localization l10) should see po/README.md
(a po file is a Portable Object file that holds the translations).
Issues which are security relevant should be disclosed privately to
the Git Security mailing list git-security@googlegroups.com.
The maintainer frequently sends the "What's cooking" reports that
list the current status of various development topics to the mailing
list. The discussion following them give a good reference for
project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very
first version. He described the tool as "the stupid content tracker"
and the name as (depending on your mood):
random three-letter combination that is pronounceable, and not
actually used by any common UNIX command. The fact that it is a
mispronunciation of "get" may or may not be relevant.
stupid. contemptible and despicable. simple. Take your pick from the
dictionary of slang.
"global information tracker": you're in a good mood, and it actually
works for you. Angels sing, and a light suddenly fills the room.
"goddamn idiotic truckload of sh*t": when it breaks
