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Regression fix.
* mt/init-template-userpath-fix:
init: fix bug regarding ~/ expansion in init.templateDir
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We used to read the init.templateDir setting at builtin/init-db.c using
a git_config() callback that, in turn, called git_config_pathname(). To
simplify the config reading logic at this file and plug a memory leak,
this was replaced by a direct call to git_config_get_value() at
e4de4502e6 ("init: remove git_init_db_config() while fixing leaks",
2021-03-14). However, this function doesn't provide path expanding
semantics, like git_config_pathname() does, so paths with '~/' and
'~user/' are treated literally. This makes 'git init' fail to handle
init.templateDir paths using these constructs:
$ git config init.templateDir '~/templates_dir'
$ git init
'warning: templates not found in ~/templates_dir'
Replace the git_config_get_value() call by git_config_get_pathname(),
which does the '~/' and '~user/' expansions. Also add a regression test.
Note that unlike git_config_get_value(), the config cache does not own
the memory for the path returned by git_config_get_pathname(), so we
must free() it.
Reported on IRC by rkta.
Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Plug or annotate remaining leaks that trigger while running the
very basic set of tests.
* ah/plugleaks:
transport: also free remote_refs in transport_disconnect()
parse-options: don't leak alias help messages
parse-options: convert bitfield values to use binary shift
init-db: silence template_dir leak when converting to absolute path
init: remove git_init_db_config() while fixing leaks
worktree: fix leak in dwim_branch()
clone: free or UNLEAK further pointers when finished
reset: free instead of leaking unneeded ref
symbolic-ref: don't leak shortened refname in check_symref()
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template_dir starts off pointing to either argv or nothing. However if
the value supplied in argv is a relative path, absolute_pathdup() is
used to turn it into an absolute path. absolute_pathdup() allocates
a new string, and we then "leak" it when cmd_init_db() completes.
We don't bother to actually free the return value (instead we UNLEAK
it), because there's no significant advantage to doing so here.
Correctly freeing it would require more significant changes to code flow
which would be more noisy than beneficial.
Signed-off-by: Andrzej Hunt <ajrhunt@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The primary goal of this change is to stop leaking init_db_template_dir.
This leak can happen because:
1. git_init_db_config() allocates new memory into init_db_template_dir
without first freeing the existing value.
2. init_db_template_dir might already contain data, either because:
2.1 git_config() can be invoked twice with this callback in a single
process - at least 2 allocations are likely.
2.2 A single git_config() allocation can invoke the callback multiple
times for a given key (see further explanation in the function
docs) - each of those calls will trigger another leak.
The simplest fix for the leak would be to free(init_db_template_dir)
before overwriting it. Instead we choose to convert to fetching
init.templatedir via git_config_get_value() as that is more explicit,
more efficient, and avoids allocations (the returned result is owned by
the config cache, so we aren't responsible for freeing it).
If we remove init_db_template_dir, git_init_db_config() ends up being
responsible only for forwarding core.* config values to
platform_core_config(). However platform_core_config() already ignores
non-core.* config values, so we can safely remove git_init_db_config()
and invoke git_config() directly with platform_core_config() as the
callback.
The platform_core_config forwarding was originally added in:
287853392a (mingw: respect core.hidedotfiles = false in git-init again, 2019-03-11
And I suspect the potential for a leak existed since the original
implementation of git_init_db_config in:
90b45187ba (Add `init.templatedir` configuration variable., 2010-02-17)
LSAN output from t0001:
Direct leak of 73 byte(s) in 1 object(s) allocated from:
#0 0x49a859 in realloc /home/abuild/rpmbuild/BUILD/llvm-11.0.0.src/build/../projects/compiler-rt/lib/asan/asan_malloc_linux.cpp:164:3
#1 0x9a7276 in xrealloc /home/ahunt/oss-fuzz/git/wrapper.c:126:8
#2 0x9362ad in strbuf_grow /home/ahunt/oss-fuzz/git/strbuf.c:98:2
#3 0x936eaa in strbuf_add /home/ahunt/oss-fuzz/git/strbuf.c:295:2
#4 0x868112 in strbuf_addstr /home/ahunt/oss-fuzz/git/./strbuf.h:304:2
#5 0x86a8ad in expand_user_path /home/ahunt/oss-fuzz/git/path.c:758:2
#6 0x720bb1 in git_config_pathname /home/ahunt/oss-fuzz/git/config.c:1287:10
#7 0x5960e2 in git_init_db_config /home/ahunt/oss-fuzz/git/builtin/init-db.c:161:11
#8 0x7255b8 in configset_iter /home/ahunt/oss-fuzz/git/config.c:1982:7
#9 0x7253fc in repo_config /home/ahunt/oss-fuzz/git/config.c:2311:2
#10 0x725ca7 in git_config /home/ahunt/oss-fuzz/git/config.c:2399:2
#11 0x593e8d in create_default_files /home/ahunt/oss-fuzz/git/builtin/init-db.c:225:2
#12 0x5935c6 in init_db /home/ahunt/oss-fuzz/git/builtin/init-db.c:449:11
#13 0x59588e in cmd_init_db /home/ahunt/oss-fuzz/git/builtin/init-db.c:714:9
#14 0x4cd60d in run_builtin /home/ahunt/oss-fuzz/git/git.c:453:11
#15 0x4cb2da in handle_builtin /home/ahunt/oss-fuzz/git/git.c:704:3
#16 0x4ccc37 in run_argv /home/ahunt/oss-fuzz/git/git.c:771:4
#17 0x4cac29 in cmd_main /home/ahunt/oss-fuzz/git/git.c:902:19
#18 0x69c4de in main /home/ahunt/oss-fuzz/git/common-main.c:52:11
#19 0x7f23552d6349 in __libc_start_main (/lib64/libc.so.6+0x24349)
Signed-off-by: Andrzej Hunt <ajrhunt@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In 552955ed7f ("clone: use more conventional config/option layering",
2020-10-01), clone learned to read configuration options earlier in its
execution, before creating the new repository. However, that led to a
problem: if the core.bare setting is set to false in the global config,
cloning a bare repository segfaults. This happens because the
repository is falsely thought to be non-bare, but clone has set the work
tree to NULL, which is then dereferenced.
The code to initialize the repository already considers the fact that a
user might want to override the --bare option for git init, but it
doesn't take into account clone, which uses a different option. Let's
just check that the work tree is not NULL, since that's how clone
indicates that the repository is bare. This is also the case for git
init, so we won't be regressing that case.
Reported-by: Joseph Vusich <jvusich@amazon.com>
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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We are about to introduce a message giving users running `git init` some
advice about `init.defaultBranch`. This will necessarily be done in
`repo_default_branch_name()`.
Not all code paths want to show that advice, though. In particular, the
`git clone` codepath _specifically_ asks for `init_db()` to be quiet,
via the `INIT_DB_QUIET` flag.
In preparation for showing users above-mentioned advice, let's change
the function signature of `get_default_branch_name()` to accept the
parameter `quiet`.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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If a user is cloning a SHA-1 repository with GIT_DEFAULT_HASH set to
"sha256", then we can end up with a repository where the repository
format version is 0 but the extensions.objectformat key is set to
"sha256". This is both wrong (the user has a SHA-1 repository) and
nonfunctional (because the extension cannot be used in a v0 repository).
This happens because in a clone, we initially set up the repository, and
then change its algorithm based on what the remote side tells us it's
using. We've initially set up the repository as SHA-256 in this case,
and then later on reset the repository version without clearing the
extension.
We could just always set the extension in this case, but that would mean
that our SHA-1 repositories weren't compatible with older Git versions,
even though there's no reason why they shouldn't be. And we also don't
want to initialize the repository as SHA-1 initially, since that means
if we're cloning an empty repository, we'll have failed to honor the
GIT_DEFAULT_HASH variable and will end up with a SHA-1 repository, not a
SHA-256 repository.
Neither of those are appealing, so let's tell the repository
initialization code if we're doing a reinit like this, and if so, to
clear the extension if we're using SHA-1. This makes sure we produce a
valid and functional repository and doesn't break any of our other use
cases.
Reported-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The intention of `git init --separate-work-dir=<path>` is to move the
.git/ directory to a location outside of the main worktree. When used
within a linked worktree, however, rather than moving the .git/
directory as intended, it instead incorrectly moves the worktree's
.git/worktrees/<id> directory to <path>, thus disconnecting the linked
worktree from its parent repository and breaking the worktree in the
process since its local .git file no longer points at a location at
which it can find the object database. Fix this broken behavior.
An intentional side-effect of this change is that it also closes a
loophole not caught by ccf236a23a (init: disallow --separate-git-dir
with bare repository, 2020-08-09) in which the check to prevent
--separate-git-dir being used in conjunction with a bare repository was
unable to detect the invalid combination when invoked from within a
linked worktree. Therefore, add a test to verify that this loophole is
closed, as well.
Reported-by: Henré Botha <henrebotha@gmail.com>
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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A linked worktree's .git file is a "gitfile" pointing at the
.git/worktrees/<id> directory within the repository. When `git init
--separate-git-dir=<path>` is used on an existing repository to relocate
the repository's .git/ directory to a different location, it neglects to
update the .git files of linked worktrees, thus breaking the worktrees
by making it impossible for them to locate the repository. Fix this by
teaching --separate-git-dir to repair the .git file of each linked
worktree to point at the new repository location.
Reported-by: Henré Botha <henrebotha@gmail.com>
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The purpose of "git init --separate-git-dir" is to initialize a
new project with the repository separate from the working tree,
or, in the case of an existing project, to move the repository
(the .git/ directory) out of the working tree. It does not make
sense to use --separate-git-dir with a bare repository for which
there is no working tree, so disallow its use with bare
repositories.
* es/init-no-separate-git-dir-in-bare:
init: disallow --separate-git-dir with bare repository
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The purpose of "git init --separate-git-dir" is to separate the
repository from the worktree. This is true even when --separate-git-dir
is used on an existing worktree, in which case, it moves the .git/
subdirectory to a new location outside the worktree.
However, an outright bare repository (such as one created by "git init
--bare"), has no worktree, so using --separate-git-dir to separate it
from its non-existent worktree is nonsensical. Therefore, make it an
error to use --separate-git-dir on a bare repository.
Implementation note: "git init" considers a repository bare if told so
explicitly via --bare or if it guesses it to be so based upon
heuristics. In the explicit --bare case, a conflict with
--separate-git-dir is easy to detect early. In the guessed case,
however, the conflict can only be detected once "bareness" is guessed,
which happens after "git init" has begun creating the repository.
Technically, we can get by with a single late check which would cover
both cases, however, erroring out early, when possible, without leaving
detritus provides a better user experience.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Now that we have a complete SHA-256 implementation in Git, let's enable
it so people can use it. Remove the ENABLE_SHA256 define constant
everywhere it's used. Add tests for initializing a repository with
SHA-256.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Reviewed-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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We just introduced the command-line option
`--initial-branch=<branch-name>` to allow initializing a new repository
with a different initial branch than the hard-coded one.
To allow users to override the initial branch name more permanently
(i.e. without having to specify the name manually for each and every
`git init` invocation), let's introduce the `init.defaultBranch` config
setting.
Helped-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Helped-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Don Goodman-Wilson <don@goodman-wilson.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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There is a growing number of projects and companies desiring to change
the main branch name of their repositories (see e.g.
https://twitter.com/mislav/status/1270388510684598272 for background on
this).
To change that branch name for new repositories, currently the only way
to do that automatically is by copying all of Git's template directory,
then hard-coding the desired default branch name into the `.git/HEAD`
file, and then configuring `init.templateDir` to point to those copied
template files.
To make this process much less cumbersome, let's introduce a new option:
`--initial-branch=<branch-name>`.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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SHA-256 transition continues.
* bc/sha-256-part-1-of-4: (22 commits)
fast-import: add options for rewriting submodules
fast-import: add a generic function to iterate over marks
fast-import: make find_marks work on any mark set
fast-import: add helper function for inserting mark object entries
fast-import: permit reading multiple marks files
commit: use expected signature header for SHA-256
worktree: allow repository version 1
init-db: move writing repo version into a function
builtin/init-db: add environment variable for new repo hash
builtin/init-db: allow specifying hash algorithm on command line
setup: allow check_repository_format to read repository format
t/helper: make repository tests hash independent
t/helper: initialize repository if necessary
t/helper/test-dump-split-index: initialize git repository
t6300: make hash algorithm independent
t6300: abstract away SHA-1-specific constants
t: use hash-specific lookup tables to define test constants
repository: require a build flag to use SHA-256
hex: add functions to parse hex object IDs in any algorithm
hex: introduce parsing variants taking hash algorithms
...
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`real_path()` returns result from a shared buffer, inviting subtle
reentrance bugs. One of these bugs occur when invoked this way:
set_git_dir(real_path(git_dir))
In this case, `real_path()` has reentrance:
real_path
read_gitfile_gently
repo_set_gitdir
setup_git_env
set_git_dir_1
set_git_dir
Later, `set_git_dir()` uses its now-dead parameter:
!is_absolute_path(path)
Fix this by using a dedicated `strbuf` to hold `strbuf_realpath()`.
Signed-off-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When we perform a clone, we won't know the remote side's hash algorithm
until we've read the heads. Consequently, we'll need to rewrite the
repository format version and hash algorithm once we know what the
remote side has. Move the code that does this into its own function so
that we can call it from clone in the future.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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For the foreseeable future, SHA-1 will be the default algorithm for Git.
However, when running the testsuite, we want to be able to test an
arbitrary algorithm. It would be quite burdensome and very untidy to
have to specify the algorithm we'd like to test every time we
initialized a new repository somewhere in the testsuite, so add an
environment variable to allow us to specify the default hash algorithm
for Git.
This has the benefit that we can set it once for the entire testsuite
and not have to think about it. In the future, users can also use it to
set the default for their repositories if they would like to do so.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Allow the user to specify the hash algorithm on the command line by
using the --object-format option to git init. Validate that the user is
not attempting to reinitialize a repository with a different hash
algorithm. Ensure that if we are writing a non-SHA-1 repository that we
set the repository version to 1 and write the objectFormat extension.
Restrict this option to work only when ENABLE_SHA256 is set until the
codebase is in a situation to fully support this.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In some cases, we will want to not only check the repository format, but
extract the information that we've gained. To do so, allow
check_repository_format to take a pointer to struct repository_format.
Allow passing NULL for this argument if we're not interested in the
information, and pass NULL for all existing callers. A future patch
will make use of this information.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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A relative pathname given to "git init --template=<path> <repo>"
ought to be relative to the directory "git init" gets invoked in,
but it instead was made relative to the repository, which has been
corrected.
* nd/init-relative-template-fix:
init: make --template path relative to $CWD
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During git-init we chdir() to the target directory, but --template is
not adjusted. So it's relative to the target directory instead of
current directory.
It would be ok if it's documented, but --template in git-init.txt
mentions nothing about this behavior. Change it to be relative to $CWD,
which is much more intuitive.
The changes in the test suite show that this relative-to-target behavior
is actually used. I just hope that it's only used in the test suite and
it's safe to change. Otherwise, the other option is just document
it (i.e. relative to target dir) and move on.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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"git init" forgot to read platform-specific repository
configuration, which made Windows port to ignore settings of
core.hidedotfiles, for example.
* js/init-db-update-for-mingw:
mingw: respect core.hidedotfiles = false in git-init again
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The setup code has been cleaned up to avoid leaks around the
repository_format structure.
* ma/clear-repository-format:
setup: fix memory leaks with `struct repository_format`
setup: free old value before setting `work_tree`
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This is a brown paper bag. When adding the tests, we actually failed
to verify that the config variable is heeded in git-init at all. And
when changing the original patch that marked the .git/ directory as
hidden after reading the config, it was lost on this developer that
the new code would use the hide_dotfiles variable before the config
was read.
The fix is obvious: read the (limited, pre-init) config *before*
creating the .git/ directory.
Please note that we cannot remove the identical-looking `git_config()`
call from `create_default_files()`: we create the `.git/` directory
between those calls. If we removed it, and if the parent directory is
in a Git worktree, and if that worktree's `.git/config` contained any
`init.templatedir` setting, we would all of a sudden pick that up.
This fixes https://github.com/git-for-windows/git/issues/789
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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After we set up a `struct repository_format`, it owns various pieces of
allocated memory. We then either use those members, because we decide we
want to use the "candidate" repository format, or we discard the
candidate / scratch space. In the first case, we transfer ownership of
the memory to a few global variables. In the latter case, we just
silently drop the struct and end up leaking memory.
Introduce an initialization macro `REPOSITORY_FORMAT_INIT` and a
function `clear_repository_format()`, to be used on each side of
`read_repository_format()`. To have a clear and simple memory ownership,
let all users of `struct repository_format` duplicate the strings that
they take from it, rather than stealing the pointers.
Call `clear_...()` at the start of `read_...()` instead of just zeroing
the struct, since we sometimes enter the function multiple times. Thus,
it is important to initialize the struct before calling `read_...()`, so
document that. It's also important because we might not even call
`read_...()` before we call `clear_...()`, see, e.g., builtin/init-db.c.
Teach `read_...()` to clear the struct on error, so that it is reset to
a safe state, and document this. (In `setup_git_directory_gently()`, we
look at `repo_fmt.hash_algo` even if `repo_fmt.version` is -1, which we
weren't actually supposed to do per the API. After this commit, that's
ok.)
We inherit the existing code's combining "error" and "no version found".
Both are signalled through `version == -1` and now both cause us to
clear any partial configuration we have picked up. For "extensions.*",
that's fine, since they require a positive version number. For
"core.bare" and "core.worktree", we're already verifying that we have a
non-negative version number before using them.
Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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There were many places the code relied on the string returned from
getenv() to be non-volatile, which is not true, that have been
corrected.
* jk/save-getenv-result:
builtin_diff(): read $GIT_DIFF_OPTS closer to use
merge-recursive: copy $GITHEAD strings
init: make a copy of $GIT_DIR string
config: make a copy of $GIT_CONFIG string
commit: copy saved getenv() result
get_super_prefix(): copy getenv() result
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We pass the result of getenv("GIT_DIR") to init_db() and assume that the
string remains valid. But that's not guaranteed across calls to setenv()
or even getenv(), although it often works in practice. Let's make a copy
of the string so that we follow the rules.
Note that we need to mark it with UNLEAK(), since the value persists
until the end of program (but we have no opportunity to free it).
This patch also handles $GIT_WORK_TREE the same way. It actually doesn't
have as long a lifetime and is probably fine, but it's simpler to just
treat the two side-by-side variables the same.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When we define a parse-options callback, the flags we put in the option
struct must match what the callback expects. For example, a callback
which does not handle the "unset" parameter should only be used with
PARSE_OPT_NONEG. But since the callback and the option struct are not
defined next to each other, it's easy to get this wrong (as earlier
patches in this series show).
Fortunately, the compiler can help us here: compiling with
-Wunused-parameters can show us which callbacks ignore their "unset"
parameters (and likewise, ones that ignore "arg" expect to be triggered
with PARSE_OPT_NOARG).
But after we've inspected a callback and determined that all of its
callers use the right flags, what do we do next? We'd like to silence
the compiler warning, but do so in a way that will catch any wrong calls
in the future.
We can do that by actually checking those variables and asserting that
they match our expectations. Because this is such a common pattern,
we'll introduce some helper macros. The resulting messages aren't
as descriptive as we could make them, but the file/line information from
BUG() is enough to identify the problem (and anyway, the point is that
these should never be seen).
Each of the annotated callbacks in this patch triggers
-Wunused-parameters, and was manually inspected to make sure all callers
use the correct options (so none of these BUGs should be triggerable).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When we initially added the strbuf_readlink() function in
b11b7e13f4 (Add generic 'strbuf_readlink()' helper function,
2008-12-17), the point was that we generally have a _guess_
as to the correct size based on the stat information, but we
can't necessarily trust it.
Over the years, a few callers have grown up that simply pass
in 0, even though they have the stat information. Let's have
them pass in their hint for consistency (and in theory
efficiency, since it may avoid an extra resize/syscall loop,
but neither location is probably performance critical).
Note that st.st_size is actually an off_t, so in theory we
need xsize_t() here. But none of the other callsites use it,
and since this is just a hint, it doesn't matter either way
(if we wrap we'll simply start with a too-small hint and
then eventually complain when we cannot allocate the
memory).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Message fix.
* rd/init-typo:
init: fix grammar in "templates not found" msg
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Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In d8193743e08 (usage.c: add BUG() function, 2017-05-12), a new macro
was introduced to use for reporting bugs instead of die(). It was then
subsequently used to convert one single caller in 588a538ae55
(setup_git_env: convert die("BUG") to BUG(), 2017-05-12).
The cover letter of the patch series containing this patch
(cf 20170513032414.mfrwabt4hovujde2@sigill.intra.peff.net) is not
terribly clear why only one call site was converted, or what the plan
is for other, similar calls to die() to report bugs.
Let's just convert all remaining ones in one fell swoop.
This trick was performed by this invocation:
sed -i 's/die("BUG: /BUG("/g' $(git grep -l 'die("BUG' \*.c)
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This is more consistent with the project style. The majority of Git's
source files use dashes in preference to underscores in their file names.
Signed-off-by: Stefan Beller <sbeller@google.com>
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Rename C++ keyword in order to bring the codebase closer to being able
to be compiled with a C++ compiler.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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It's a common pattern in git commands to allocate some
memory that should last for the lifetime of the program and
then not bother to free it, relying on the OS to throw it
away.
This keeps the code simple, and it's fast (we don't waste
time traversing structures or calling free at the end of the
program). But it also triggers warnings from memory-leak
checkers like valgrind or LSAN. They know that the memory
was still allocated at program exit, but they don't know
_when_ the leaked memory stopped being useful. If it was
early in the program, then it's probably a real and
important leak. But if it was used right up until program
exit, it's not an interesting leak and we'd like to suppress
it so that we can see the real leaks.
This patch introduces an UNLEAK() macro that lets us do so.
To understand its design, let's first look at some of the
alternatives.
Unfortunately the suppression systems offered by
leak-checking tools don't quite do what we want. A
leak-checker basically knows two things:
1. Which blocks were allocated via malloc, and the
callstack during the allocation.
2. Which blocks were left un-freed at the end of the
program (and which are unreachable, but more on that
later).
Their suppressions work by mentioning the function or
callstack of a particular allocation, and marking it as OK
to leak. So imagine you have code like this:
int cmd_foo(...)
{
/* this allocates some memory */
char *p = some_function();
printf("%s", p);
return 0;
}
You can say "ignore allocations from some_function(),
they're not leaks". But that's not right. That function may
be called elsewhere, too, and we would potentially want to
know about those leaks.
So you can say "ignore the callstack when main calls
some_function". That works, but your annotations are
brittle. In this case it's only two functions, but you can
imagine that the actual allocation is much deeper. If any of
the intermediate code changes, you have to update the
suppression.
What we _really_ want to say is that "the value assigned to
p at the end of the function is not a real leak". But
leak-checkers can't understand that; they don't know about
"p" in the first place.
However, we can do something a little bit tricky if we make
some assumptions about how leak-checkers work. They
generally don't just report all un-freed blocks. That would
report even globals which are still accessible when the
leak-check is run. Instead they take some set of memory
(like BSS) as a root and mark it as "reachable". Then they
scan the reachable blocks for anything that looks like a
pointer to a malloc'd block, and consider that block
reachable. And then they scan those blocks, and so on,
transitively marking anything reachable from a global as
"not leaked" (or at least leaked in a different category).
So we can mark the value of "p" as reachable by putting it
into a variable with program lifetime. One way to do that is
to just mark "p" as static. But that actually affects the
run-time behavior if the function is called twice (you
aren't likely to call main() twice, but some of our cmd_*()
functions are called from other commands).
Instead, we can trick the leak-checker by putting the value
into _any_ reachable bytes. This patch keeps a global
linked-list of bytes copied from "unleaked" variables. That
list is reachable even at program exit, which confers
recursive reachability on whatever values we unleak.
In other words, you can do:
int cmd_foo(...)
{
char *p = some_function();
printf("%s", p);
UNLEAK(p);
return 0;
}
to annotate "p" and suppress the leak report.
But wait, couldn't we just say "free(p)"? In this toy
example, yes. But UNLEAK()'s byte-copying strategy has
several advantages over actually freeing the memory:
1. It's recursive across structures. In many cases our "p"
is not just a pointer, but a complex struct whose
fields may have been allocated by a sub-function. And
in some cases (e.g., dir_struct) we don't even have a
function which knows how to free all of the struct
members.
By marking the struct itself as reachable, that confers
reachability on any pointers it contains (including those
found in embedded structs, or reachable by walking
heap blocks recursively.
2. It works on cases where we're not sure if the value is
allocated or not. For example:
char *p = argc > 1 ? argv[1] : some_function();
It's safe to use UNLEAK(p) here, because it's not
freeing any memory. In the case that we're pointing to
argv here, the reachability checker will just ignore
our bytes.
3. Likewise, it works even if the variable has _already_
been freed. We're just copying the pointer bytes. If
the block has been freed, the leak-checker will skip
over those bytes as uninteresting.
4. Because it's not actually freeing memory, you can
UNLEAK() before we are finished accessing the variable.
This is helpful in cases like this:
char *p = some_function();
return another_function(p);
Writing this with free() requires:
int ret;
char *p = some_function();
ret = another_function(p);
free(p);
return ret;
But with unleak we can just write:
char *p = some_function();
UNLEAK(p);
return another_function(p);
This patch adds the UNLEAK() macro and enables it
automatically when Git is compiled with SANITIZE=leak. In
normal builds it's a noop, so we pay no runtime cost.
It also adds some UNLEAK() annotations to show off how the
feature works. On top of other recent leak fixes, these are
enough to get t0000 and t0001 to pass when compiled with
LSAN.
Note the case in commit.c which actually converts a
strbuf_release() into an UNLEAK. This code was already
non-leaky, but the free didn't do anything useful, since
we're exiting. Converting it to an annotation means that
non-leak-checking builds pay no runtime cost. The cost is
minimal enough that it's probably not worth going on a
crusade to convert these kinds of frees to UNLEAKS. I did it
here for consistency with the "sb" leak (though it would
have been equally correct to go the other way, and turn them
both into strbuf_release() calls).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Stop including config.h by default in cache.h. Instead only include
config.h in those files which require use of the config system.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In 4ac9006f832 (real_path: have callers use real_pathdup and
strbuf_realpath, 2016-12-12), we changed the xstrdup(real_path())
pattern to use real_pathdup() directly.
The problem with this change is that real_path() calls
strbuf_realpath() with die_on_error = 1 while real_pathdup() calls
it with die_on_error = 0. Meaning that in cases where real_path()
causes Git to die() with an error message, real_pathdup() is silent
and returns NULL instead.
The callers, however, are ill-prepared for that change, as they expect
the return value to be non-NULL (and otherwise the function died
with an appropriate error message).
Fix this by extending real_pathdup()'s signature to accept the
die_on_error flag and simply pass it through to strbuf_realpath(),
and then adjust all callers after a careful audit whether they would
handle NULLs well.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When core.logallrefupdates is true, we only create a new reflog for refs
that are under certain well-known hierarchies. The reason is that we
know that some hierarchies (like refs/tags) are not meant to change, and
that unknown hierarchies might not want reflogs at all (e.g., a
hypothetical refs/foo might be meant to change often and drop old
history immediately).
However, sometimes it is useful to override this decision and simply log
for all refs, because the safety and audit trail is more important than
the performance implications of keeping the log around.
This patch introduces a new "always" mode for the core.logallrefupdates
option which will log updates to everything under refs/, regardless
where in the hierarchy it is (we still will not log things like
ORIG_HEAD and FETCH_HEAD, which are known to be transient).
Based-on-patch-by: Jeff King <peff@peff.net>
Signed-off-by: Cornelius Weig <cornelius.weig@tngtech.com>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Migrate callers of real_path() who duplicate the retern value to use
real_pathdup or strbuf_realpath.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Junio C Hamano
Matheus Tavares
Andrzej Hunt
brian m. carlson
Johannes Schindelin
Eric Sunshine
Don Goodman-Wilson
Alexandr Miloslavskiy
Nguyễn Thái Ngọc Duy
Martin Ågren
Jeff King
Robert P. J. Day
Stefan Beller
Brandon Williams
Cornelius Weig