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git/common-main.c

85 lines
2.1 KiB

#include "cache.h"
#include "exec-cmd.h"
#include "attr.h"
add an extra level of indirection to main() There are certain startup tasks that we expect every git process to do. In some cases this is just to improve the quality of the program (e.g., setting up gettext()). In others it is a requirement for using certain functions in libgit.a (e.g., system_path() expects that you have called git_extract_argv0_path()). Most commands are builtins and are covered by the git.c version of main(). However, there are still a few external commands that use their own main(). Each of these has to remember to include the correct startup sequence, and we are not always consistent. Rather than just fix the inconsistencies, let's make this harder to get wrong by providing a common main() that can run this standard startup. We basically have two options to do this: - the compat/mingw.h file already does something like this by adding a #define that replaces the definition of main with a wrapper that calls mingw_startup(). The upside is that the code in each program doesn't need to be changed at all; it's rewritten on the fly by the preprocessor. The downside is that it may make debugging of the startup sequence a bit more confusing, as the preprocessor is quietly inserting new code. - the builtin functions are all of the form cmd_foo(), and git.c's main() calls them. This is much more explicit, which may make things more obvious to somebody reading the code. It's also more flexible (because of course we have to figure out _which_ cmd_foo() to call). The downside is that each of the builtins must define cmd_foo(), instead of just main(). This patch chooses the latter option, preferring the more explicit approach, even though it is more invasive. We introduce a new file common-main.c, with the "real" main. It expects to call cmd_main() from whatever other objects it is linked against. We link common-main.o against anything that links against libgit.a, since we know that such programs will need to do this setup. Note that common-main.o can't actually go inside libgit.a, as the linker would not pick up its main() function automatically (it has no callers). The rest of the patch is just adjusting all of the various external programs (mostly in t/helper) to use cmd_main(). I've provided a global declaration for cmd_main(), which means that all of the programs also need to match its signature. In particular, many functions need to switch to "const char **" instead of "char **" for argv. This effect ripples out to a few other variables and functions, as well. This makes the patch even more invasive, but the end result is much better. We should be treating argv strings as const anyway, and now all programs conform to the same signature (which also matches the way builtins are defined). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
6 years ago
/*
* Many parts of Git have subprograms communicate via pipe, expect the
* upstream of a pipe to die with SIGPIPE when the downstream of a
* pipe does not need to read all that is written. Some third-party
* programs that ignore or block SIGPIPE for their own reason forget
* to restore SIGPIPE handling to the default before spawning Git and
* break this carefully orchestrated machinery.
*
* Restore the way SIGPIPE is handled to default, which is what we
* expect.
*/
static void restore_sigpipe_to_default(void)
{
sigset_t unblock;
sigemptyset(&unblock);
sigaddset(&unblock, SIGPIPE);
sigprocmask(SIG_UNBLOCK, &unblock, NULL);
signal(SIGPIPE, SIG_DFL);
}
int main(int argc, const char **argv)
add an extra level of indirection to main() There are certain startup tasks that we expect every git process to do. In some cases this is just to improve the quality of the program (e.g., setting up gettext()). In others it is a requirement for using certain functions in libgit.a (e.g., system_path() expects that you have called git_extract_argv0_path()). Most commands are builtins and are covered by the git.c version of main(). However, there are still a few external commands that use their own main(). Each of these has to remember to include the correct startup sequence, and we are not always consistent. Rather than just fix the inconsistencies, let's make this harder to get wrong by providing a common main() that can run this standard startup. We basically have two options to do this: - the compat/mingw.h file already does something like this by adding a #define that replaces the definition of main with a wrapper that calls mingw_startup(). The upside is that the code in each program doesn't need to be changed at all; it's rewritten on the fly by the preprocessor. The downside is that it may make debugging of the startup sequence a bit more confusing, as the preprocessor is quietly inserting new code. - the builtin functions are all of the form cmd_foo(), and git.c's main() calls them. This is much more explicit, which may make things more obvious to somebody reading the code. It's also more flexible (because of course we have to figure out _which_ cmd_foo() to call). The downside is that each of the builtins must define cmd_foo(), instead of just main(). This patch chooses the latter option, preferring the more explicit approach, even though it is more invasive. We introduce a new file common-main.c, with the "real" main. It expects to call cmd_main() from whatever other objects it is linked against. We link common-main.o against anything that links against libgit.a, since we know that such programs will need to do this setup. Note that common-main.o can't actually go inside libgit.a, as the linker would not pick up its main() function automatically (it has no callers). The rest of the patch is just adjusting all of the various external programs (mostly in t/helper) to use cmd_main(). I've provided a global declaration for cmd_main(), which means that all of the programs also need to match its signature. In particular, many functions need to switch to "const char **" instead of "char **" for argv. This effect ripples out to a few other variables and functions, as well. This makes the patch even more invasive, but the end result is much better. We should be treating argv strings as const anyway, and now all programs conform to the same signature (which also matches the way builtins are defined). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
6 years ago
{
int result;
struct strbuf tmp = STRBUF_INIT;
trace2_initialize_clock();
/*
* Always open file descriptors 0/1/2 to avoid clobbering files
* in die(). It also avoids messing up when the pipes are dup'ed
* onto stdin/stdout/stderr in the child processes we spawn.
*/
sanitize_stdfds();
restore_sigpipe_to_default();
git_resolve_executable_dir(argv[0]);
git_setup_gettext();
initialize_the_repository();
attr_start();
trace2_initialize();
trace2_cmd_start(argv);
trace2_collect_process_info(TRACE2_PROCESS_INFO_STARTUP);
if (!strbuf_getcwd(&tmp))
tmp_original_cwd = strbuf_detach(&tmp, NULL);
result = cmd_main(argc, argv);
/* Not exit(3), but a wrapper calling our common_exit() */
exit(result);
}
static void check_bug_if_BUG(void)
{
if (!bug_called_must_BUG)
return;
BUG("on exit(): had bug() call(s) in this process without explicit BUG_if_bug()");
}
/* We wrap exit() to call common_exit() in git-compat-util.h */
int common_exit(const char *file, int line, int code)
{
common-main.c: call exit(), don't return Change the main() function to call "exit()" instead of ending with a "return" statement. The "exit()" function is our own wrapper that calls trace2_cmd_exit_fl() for us, from git-compat-util.h: #define exit(code) exit(trace2_cmd_exit_fl(__FILE__, __LINE__, (code))) That "exit()" wrapper has been in use ever since ee4512ed481 (trace2: create new combined trace facility, 2019-02-22). This changes nothing about how we "exit()", as we'd invoke "trace2_cmd_exit_fl()" in both cases due to the wrapper, this change makes it easier to reason about this code, as we're now always obviously relying on our "exit()" wrapper. There is already code immediately downstream of our "main()" which has a hard reliance on that, e.g. the various "exit()" calls downstream of "cmd_main()" in "git.c". We even had a comment in "t/helper/test-trace2.c" that seemed to be confused about how the "exit()" wrapper interacted with uses of "return", even though it was introduced in the same trace2 series in a15860dca3f (trace2: t/helper/test-trace2, t0210.sh, t0211.sh, t0212.sh, 2019-02-22), after the aforementioned ee4512ed481. Perhaps it pre-dated the "exit()" wrapper? This change makes the "trace2_cmd_exit()" macro orphaned, we now always use "trace2_cmd_exit_fl()" directly, but let's keep that simpler example in place. Even if we're unlikely to get another "main()" other than the one in our "common-main.c", there's some value in having the API documentation and example discuss a simpler version that doesn't require an "exit()" wrapper macro. Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
10 months ago
/*
* For non-POSIX systems: Take the lowest 8 bits of the "code"
* to e.g. turn -1 into 255. On a POSIX system this is
* redundant, see exit(3) and wait(2), but as it doesn't harm
* anything there we don't need to guard this with an "ifdef".
common-main.c: call exit(), don't return Change the main() function to call "exit()" instead of ending with a "return" statement. The "exit()" function is our own wrapper that calls trace2_cmd_exit_fl() for us, from git-compat-util.h: #define exit(code) exit(trace2_cmd_exit_fl(__FILE__, __LINE__, (code))) That "exit()" wrapper has been in use ever since ee4512ed481 (trace2: create new combined trace facility, 2019-02-22). This changes nothing about how we "exit()", as we'd invoke "trace2_cmd_exit_fl()" in both cases due to the wrapper, this change makes it easier to reason about this code, as we're now always obviously relying on our "exit()" wrapper. There is already code immediately downstream of our "main()" which has a hard reliance on that, e.g. the various "exit()" calls downstream of "cmd_main()" in "git.c". We even had a comment in "t/helper/test-trace2.c" that seemed to be confused about how the "exit()" wrapper interacted with uses of "return", even though it was introduced in the same trace2 series in a15860dca3f (trace2: t/helper/test-trace2, t0210.sh, t0211.sh, t0212.sh, 2019-02-22), after the aforementioned ee4512ed481. Perhaps it pre-dated the "exit()" wrapper? This change makes the "trace2_cmd_exit()" macro orphaned, we now always use "trace2_cmd_exit_fl()" directly, but let's keep that simpler example in place. Even if we're unlikely to get another "main()" other than the one in our "common-main.c", there's some value in having the API documentation and example discuss a simpler version that doesn't require an "exit()" wrapper macro. Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
10 months ago
*/
code &= 0xff;
check_bug_if_BUG();
trace2_cmd_exit_fl(file, line, code);
return code;
add an extra level of indirection to main() There are certain startup tasks that we expect every git process to do. In some cases this is just to improve the quality of the program (e.g., setting up gettext()). In others it is a requirement for using certain functions in libgit.a (e.g., system_path() expects that you have called git_extract_argv0_path()). Most commands are builtins and are covered by the git.c version of main(). However, there are still a few external commands that use their own main(). Each of these has to remember to include the correct startup sequence, and we are not always consistent. Rather than just fix the inconsistencies, let's make this harder to get wrong by providing a common main() that can run this standard startup. We basically have two options to do this: - the compat/mingw.h file already does something like this by adding a #define that replaces the definition of main with a wrapper that calls mingw_startup(). The upside is that the code in each program doesn't need to be changed at all; it's rewritten on the fly by the preprocessor. The downside is that it may make debugging of the startup sequence a bit more confusing, as the preprocessor is quietly inserting new code. - the builtin functions are all of the form cmd_foo(), and git.c's main() calls them. This is much more explicit, which may make things more obvious to somebody reading the code. It's also more flexible (because of course we have to figure out _which_ cmd_foo() to call). The downside is that each of the builtins must define cmd_foo(), instead of just main(). This patch chooses the latter option, preferring the more explicit approach, even though it is more invasive. We introduce a new file common-main.c, with the "real" main. It expects to call cmd_main() from whatever other objects it is linked against. We link common-main.o against anything that links against libgit.a, since we know that such programs will need to do this setup. Note that common-main.o can't actually go inside libgit.a, as the linker would not pick up its main() function automatically (it has no callers). The rest of the patch is just adjusting all of the various external programs (mostly in t/helper) to use cmd_main(). I've provided a global declaration for cmd_main(), which means that all of the programs also need to match its signature. In particular, many functions need to switch to "const char **" instead of "char **" for argv. This effect ripples out to a few other variables and functions, as well. This makes the patch even more invasive, but the end result is much better. We should be treating argv strings as const anyway, and now all programs conform to the same signature (which also matches the way builtins are defined). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
6 years ago
}