| commit | 55391836224af8a65f3802f4a4c87ece0f2c19a4 | [log] [tgz] |
|---|---|---|
| author | Jeff King <peff@peff.net> | Thu Oct 15 15:30:29 2020 -0400 |
| committer | Junio C Hamano <gitster@pobox.com> | Fri Oct 16 08:41:40 2020 -0700 |
| tree | a41a9695a0a402959c0133fdcd0d8f43de705561 | |
| parent | 47ae905ffb98cc4d4fd90083da6bc8dab55d9ecc [diff] |
config.mak.dev: build with -fno-common
It's an easy mistake to define a variable in a header with "int x;" when
you really meant to only declare the variable as "extern int x;"
instead. Clang and gcc will both allow this when building with
"-fcommon"; they put these "tentative definitions" in a common block
which the linker is able to resolve.
This is the default in clang and was the default in gcc until gcc-10,
since it helps some legacy code. However, we would prefer not to rely on
this because:
- using "extern" makes the intent more clear (so it's a style issue,
but it's one the compiler can help us catch)
- according to the gcc manpage, it may yield a speed and code size
penalty
So let's build explicitly with -fno-common when the DEVELOPER knob is
set, which will let developers using clang and older versions of gcc
notice these problems.
I didn't bother making this conditional on a particular version of gcc.
As far as I know, this option has been available forever in both gcc and
clang, so old versions don't need to avoid it. And we already expect gcc
and clang options throughout config.mak.dev, so it's unlikely anybody
setting the DEVELOPER knob is using anything else. It's a noop on
gcc-10, of course, but it's not worth trying to exclude it there.
Note that there's nothing to fix in the code; we already don't have any
issues here. But if you want to test the patch, you can add a bare "int
x;" into cache.h, which will cause the link step to fail.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission). To subscribe to the list, send an email with just “subscribe git” in the body to majordomo@vger.kernel.org. The mailing list archives are available at https://lore.kernel.org/git/, http://marc.info/?l=git and other archival sites.
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):