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https://github.com/git/git.git
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aec0bba106
Compiling with gcc-10, -O2, and -fsanitize=undefined results in a
compiler warning:
config.c: In function ‘git_config_copy_or_rename_section_in_file’:
config.c:3170:17: error: writing 1 byte into a region of size 0 [-Werror=stringop-overflow=]
3170 | output[0] = '\t';
| ~~~~~~~~~~^~~~~~
config.c:3076:7: note: at offset -1 to object ‘buf’ with size 1024 declared here
3076 | char buf[1024];
| ^~~
This is a false positive. The interesting lines of code are:
int i;
char *output = buf;
...
for (i = 0; buf[i] && isspace(buf[i]); i++)
; /* do nothing */
...
int offset;
offset = section_name_match(&buf[i], old_name);
if (offset > 0) {
...
output += offset + i;
if (strlen(output) > 0) {
/*
* More content means there's
* a declaration to put on the
* next line; indent with a
* tab
*/
output -= 1;
output[0] = '\t';
}
}
So we do assign output to buf initially. Later we increment it based on
"offset" and "i" and then subtract "1" from it. That latter step is what
the compiler is complaining about; it could lead to going off the left
side of the array if "output == buf" at the moment of the subtraction.
For that to be the case, then "offset + i" would have to be 0. But that
can't happen:
- we know that "offset" is at least 1, since we're in a conditional
block that checks that
- we know that "i" is not negative, since it started at 0 and only
incremented over whitespace
So the sum must be at least 1, and therefore it's OK to subtract one
from "output".
But that's not quite the whole story. Since "i" is an int, it could in
theory be possible to overflow to negative (when counting whitespace on
a very large string). But we know that's impossible because we're
counting the 1024-byte buffer we just fed to fgets(), so it can never be
larger than that.
Switching the type of "i" to "unsigned" makes the warning go away, so
let's do that.
Arguably size_t is an even better type (for this and for the other
length fields), but switching to it produces a similar but distinct
warning:
config.c: In function ‘git_config_copy_or_rename_section_in_file’:
config.c:3170:13: error: array subscript -1 is outside array bounds of ‘char[1024]’ [-Werror=array-bounds]
3170 | output[0] = '\t';
| ~~~~~~^~~
config.c:3076:7: note: while referencing ‘buf’
3076 | char buf[1024];
| ^~~
If we were to ever switch off of fgets() to strbuf_getline() or similar,
we'd probably need to use size_t to avoid other overflow problems. But
for now we know we're safe because of the small fixed size of our
buffer.
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).
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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