git/pager.c

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3.6 KiB
C
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#include "cache.h"
#include "run-command.h"
#include "sigchain.h"
#ifndef DEFAULT_PAGER
#define DEFAULT_PAGER "less"
#endif
/*
* This is split up from the rest of git so that we can do
* something different on Windows.
*/
static struct child_process pager_process = CHILD_PROCESS_INIT;
pager: don't use unsafe functions in signal handlers Since the commit a3da8821208d (pager: do wait_for_pager on signal death), we call wait_for_pager() in the pager's signal handler. The recent bug report revealed that this causes a deadlock in glibc at aborting "git log" [*1*]. When this happens, git process is left unterminated, and it can't be killed by SIGTERM but only by SIGKILL. The problem is that wait_for_pager() function does more than waiting for pager process's termination, but it does cleanups and printing errors. Unfortunately, the functions that may be used in a signal handler are very limited [*2*]. Particularly, malloc(), free() and the variants can't be used in a signal handler because they take a mutex internally in glibc. This was the cause of the deadlock above. Other than the direct calls of malloc/free, many functions calling malloc/free can't be used. strerror() is such one, either. Also the usage of fflush() and printf() in a signal handler is bad, although it seems working so far. In a safer side, we should avoid them, too. This patch tries to reduce the calls of such functions in signal handlers. wait_for_signal() takes a flag and avoids the unsafe calls. Also, finish_command_in_signal() is introduced for the same reason. There the free() calls are removed, and only waits for the children without whining at errors. [*1*] https://bugzilla.opensuse.org/show_bug.cgi?id=942297 [*2*] http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04_03 Signed-off-by: Takashi Iwai <tiwai@suse.de> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-09-04 12:35:57 +03:00
static void wait_for_pager(int in_signal)
{
pager: don't use unsafe functions in signal handlers Since the commit a3da8821208d (pager: do wait_for_pager on signal death), we call wait_for_pager() in the pager's signal handler. The recent bug report revealed that this causes a deadlock in glibc at aborting "git log" [*1*]. When this happens, git process is left unterminated, and it can't be killed by SIGTERM but only by SIGKILL. The problem is that wait_for_pager() function does more than waiting for pager process's termination, but it does cleanups and printing errors. Unfortunately, the functions that may be used in a signal handler are very limited [*2*]. Particularly, malloc(), free() and the variants can't be used in a signal handler because they take a mutex internally in glibc. This was the cause of the deadlock above. Other than the direct calls of malloc/free, many functions calling malloc/free can't be used. strerror() is such one, either. Also the usage of fflush() and printf() in a signal handler is bad, although it seems working so far. In a safer side, we should avoid them, too. This patch tries to reduce the calls of such functions in signal handlers. wait_for_signal() takes a flag and avoids the unsafe calls. Also, finish_command_in_signal() is introduced for the same reason. There the free() calls are removed, and only waits for the children without whining at errors. [*1*] https://bugzilla.opensuse.org/show_bug.cgi?id=942297 [*2*] http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04_03 Signed-off-by: Takashi Iwai <tiwai@suse.de> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-09-04 12:35:57 +03:00
if (!in_signal) {
fflush(stdout);
fflush(stderr);
}
/* signal EOF to pager */
close(1);
close(2);
pager: don't use unsafe functions in signal handlers Since the commit a3da8821208d (pager: do wait_for_pager on signal death), we call wait_for_pager() in the pager's signal handler. The recent bug report revealed that this causes a deadlock in glibc at aborting "git log" [*1*]. When this happens, git process is left unterminated, and it can't be killed by SIGTERM but only by SIGKILL. The problem is that wait_for_pager() function does more than waiting for pager process's termination, but it does cleanups and printing errors. Unfortunately, the functions that may be used in a signal handler are very limited [*2*]. Particularly, malloc(), free() and the variants can't be used in a signal handler because they take a mutex internally in glibc. This was the cause of the deadlock above. Other than the direct calls of malloc/free, many functions calling malloc/free can't be used. strerror() is such one, either. Also the usage of fflush() and printf() in a signal handler is bad, although it seems working so far. In a safer side, we should avoid them, too. This patch tries to reduce the calls of such functions in signal handlers. wait_for_signal() takes a flag and avoids the unsafe calls. Also, finish_command_in_signal() is introduced for the same reason. There the free() calls are removed, and only waits for the children without whining at errors. [*1*] https://bugzilla.opensuse.org/show_bug.cgi?id=942297 [*2*] http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04_03 Signed-off-by: Takashi Iwai <tiwai@suse.de> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-09-04 12:35:57 +03:00
if (in_signal)
finish_command_in_signal(&pager_process);
else
finish_command(&pager_process);
}
static void wait_for_pager_atexit(void)
{
wait_for_pager(0);
}
static void wait_for_pager_signal(int signo)
{
pager: don't use unsafe functions in signal handlers Since the commit a3da8821208d (pager: do wait_for_pager on signal death), we call wait_for_pager() in the pager's signal handler. The recent bug report revealed that this causes a deadlock in glibc at aborting "git log" [*1*]. When this happens, git process is left unterminated, and it can't be killed by SIGTERM but only by SIGKILL. The problem is that wait_for_pager() function does more than waiting for pager process's termination, but it does cleanups and printing errors. Unfortunately, the functions that may be used in a signal handler are very limited [*2*]. Particularly, malloc(), free() and the variants can't be used in a signal handler because they take a mutex internally in glibc. This was the cause of the deadlock above. Other than the direct calls of malloc/free, many functions calling malloc/free can't be used. strerror() is such one, either. Also the usage of fflush() and printf() in a signal handler is bad, although it seems working so far. In a safer side, we should avoid them, too. This patch tries to reduce the calls of such functions in signal handlers. wait_for_signal() takes a flag and avoids the unsafe calls. Also, finish_command_in_signal() is introduced for the same reason. There the free() calls are removed, and only waits for the children without whining at errors. [*1*] https://bugzilla.opensuse.org/show_bug.cgi?id=942297 [*2*] http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04_03 Signed-off-by: Takashi Iwai <tiwai@suse.de> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-09-04 12:35:57 +03:00
wait_for_pager(1);
sigchain_pop(signo);
raise(signo);
}
const char *git_pager(int stdout_is_tty)
{
const char *pager;
if (!stdout_is_tty)
return NULL;
pager = getenv("GIT_PAGER");
if (!pager) {
if (!pager_program)
git_config(git_default_config, NULL);
pager = pager_program;
}
if (!pager)
pager = getenv("PAGER");
if (!pager)
pager = DEFAULT_PAGER;
if (!*pager || !strcmp(pager, "cat"))
pager = NULL;
return pager;
}
void prepare_pager_args(struct child_process *pager_process, const char *pager)
{
argv_array_push(&pager_process->args, pager);
pager_process->use_shell = 1;
if (!getenv("LESS"))
argv_array_push(&pager_process->env_array, "LESS=FRX");
if (!getenv("LV"))
argv_array_push(&pager_process->env_array, "LV=-c");
}
void setup_pager(void)
{
const char *pager = git_pager(isatty(1));
if (!pager)
return;
/*
* force computing the width of the terminal before we redirect
* the standard output to the pager.
*/
(void) term_columns();
setenv("GIT_PAGER_IN_USE", "true", 1);
/* spawn the pager */
prepare_pager_args(&pager_process, pager);
pager_process.in = -1;
argv_array_push(&pager_process.env_array, "GIT_PAGER_IN_USE");
if (start_command(&pager_process))
return;
/* original process continues, but writes to the pipe */
dup2(pager_process.in, 1);
if (isatty(2))
dup2(pager_process.in, 2);
close(pager_process.in);
/* this makes sure that the parent terminates after the pager */
sigchain_push_common(wait_for_pager_signal);
pager: don't use unsafe functions in signal handlers Since the commit a3da8821208d (pager: do wait_for_pager on signal death), we call wait_for_pager() in the pager's signal handler. The recent bug report revealed that this causes a deadlock in glibc at aborting "git log" [*1*]. When this happens, git process is left unterminated, and it can't be killed by SIGTERM but only by SIGKILL. The problem is that wait_for_pager() function does more than waiting for pager process's termination, but it does cleanups and printing errors. Unfortunately, the functions that may be used in a signal handler are very limited [*2*]. Particularly, malloc(), free() and the variants can't be used in a signal handler because they take a mutex internally in glibc. This was the cause of the deadlock above. Other than the direct calls of malloc/free, many functions calling malloc/free can't be used. strerror() is such one, either. Also the usage of fflush() and printf() in a signal handler is bad, although it seems working so far. In a safer side, we should avoid them, too. This patch tries to reduce the calls of such functions in signal handlers. wait_for_signal() takes a flag and avoids the unsafe calls. Also, finish_command_in_signal() is introduced for the same reason. There the free() calls are removed, and only waits for the children without whining at errors. [*1*] https://bugzilla.opensuse.org/show_bug.cgi?id=942297 [*2*] http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04_03 Signed-off-by: Takashi Iwai <tiwai@suse.de> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-09-04 12:35:57 +03:00
atexit(wait_for_pager_atexit);
}
int pager_in_use(void)
{
const char *env;
env = getenv("GIT_PAGER_IN_USE");
return env ? git_config_bool("GIT_PAGER_IN_USE", env) : 0;
}
/*
* Return cached value (if set) or $COLUMNS environment variable (if
* set and positive) or ioctl(1, TIOCGWINSZ).ws_col (if positive),
* and default to 80 if all else fails.
*/
int term_columns(void)
{
static int term_columns_at_startup;
char *col_string;
int n_cols;
if (term_columns_at_startup)
return term_columns_at_startup;
term_columns_at_startup = 80;
col_string = getenv("COLUMNS");
if (col_string && (n_cols = atoi(col_string)) > 0)
term_columns_at_startup = n_cols;
#ifdef TIOCGWINSZ
else {
struct winsize ws;
if (!ioctl(1, TIOCGWINSZ, &ws) && ws.ws_col)
term_columns_at_startup = ws.ws_col;
}
#endif
return term_columns_at_startup;
}
/*
* How many columns do we need to show this number in decimal?
*/
decimal_width: avoid integer overflow The decimal_width function originally appeared in blame.c as "lineno_width", and was designed for calculating the print-width of small-ish integer values (line numbers in text files). In ec7ff5b, it was made into a reusable function, and in dc801e7, we started using it to align diffstats. Binary files in a diffstat show byte counts rather than line numbers, meaning they can be quite large (e.g., consider adding or removing a 2GB file). decimal_width is not up to the challenge for two reasons: 1. It takes the value as an "int", whereas large files may easily surpass this. The value may be truncated, in which case we will produce an incorrect value. 2. It counts "up" by repeatedly multiplying another integer by 10 until it surpasses the value. This can cause an infinite loop when the value is close to the largest representable integer. For example, consider using a 32-bit signed integer, and a value of 2,140,000,000 (just shy of 2^31-1). We will count up and eventually see that 1,000,000,000 is smaller than our value. The next step would be to multiply by 10 and see that 10,000,000,000 is too large, ending the loop. But we can't represent that value, and we have signed overflow. This is technically undefined behavior, but a common behavior is to lose the high bits, in which case our iterator will certainly be less than the number. So we'll keep multiplying, overflow again, and so on. This patch changes the argument to a uintmax_t (the same type we use to store the diffstat information for binary filese), and counts "down" by repeatedly dividing our value by 10. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-02-05 11:14:19 +03:00
int decimal_width(uintmax_t number)
{
decimal_width: avoid integer overflow The decimal_width function originally appeared in blame.c as "lineno_width", and was designed for calculating the print-width of small-ish integer values (line numbers in text files). In ec7ff5b, it was made into a reusable function, and in dc801e7, we started using it to align diffstats. Binary files in a diffstat show byte counts rather than line numbers, meaning they can be quite large (e.g., consider adding or removing a 2GB file). decimal_width is not up to the challenge for two reasons: 1. It takes the value as an "int", whereas large files may easily surpass this. The value may be truncated, in which case we will produce an incorrect value. 2. It counts "up" by repeatedly multiplying another integer by 10 until it surpasses the value. This can cause an infinite loop when the value is close to the largest representable integer. For example, consider using a 32-bit signed integer, and a value of 2,140,000,000 (just shy of 2^31-1). We will count up and eventually see that 1,000,000,000 is smaller than our value. The next step would be to multiply by 10 and see that 10,000,000,000 is too large, ending the loop. But we can't represent that value, and we have signed overflow. This is technically undefined behavior, but a common behavior is to lose the high bits, in which case our iterator will certainly be less than the number. So we'll keep multiplying, overflow again, and so on. This patch changes the argument to a uintmax_t (the same type we use to store the diffstat information for binary filese), and counts "down" by repeatedly dividing our value by 10. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-02-05 11:14:19 +03:00
int width;
decimal_width: avoid integer overflow The decimal_width function originally appeared in blame.c as "lineno_width", and was designed for calculating the print-width of small-ish integer values (line numbers in text files). In ec7ff5b, it was made into a reusable function, and in dc801e7, we started using it to align diffstats. Binary files in a diffstat show byte counts rather than line numbers, meaning they can be quite large (e.g., consider adding or removing a 2GB file). decimal_width is not up to the challenge for two reasons: 1. It takes the value as an "int", whereas large files may easily surpass this. The value may be truncated, in which case we will produce an incorrect value. 2. It counts "up" by repeatedly multiplying another integer by 10 until it surpasses the value. This can cause an infinite loop when the value is close to the largest representable integer. For example, consider using a 32-bit signed integer, and a value of 2,140,000,000 (just shy of 2^31-1). We will count up and eventually see that 1,000,000,000 is smaller than our value. The next step would be to multiply by 10 and see that 10,000,000,000 is too large, ending the loop. But we can't represent that value, and we have signed overflow. This is technically undefined behavior, but a common behavior is to lose the high bits, in which case our iterator will certainly be less than the number. So we'll keep multiplying, overflow again, and so on. This patch changes the argument to a uintmax_t (the same type we use to store the diffstat information for binary filese), and counts "down" by repeatedly dividing our value by 10. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-02-05 11:14:19 +03:00
for (width = 1; number >= 10; width++)
number /= 10;
return width;
}
/* returns 0 for "no pager", 1 for "use pager", and -1 for "not specified" */
int check_pager_config(const char *cmd)
{
int want = -1;
struct strbuf key = STRBUF_INIT;
const char *value = NULL;
strbuf_addf(&key, "pager.%s", cmd);
config: silence warnings for command names with invalid keys When we are running the git command "foo", we may have to look up the config keys "pager.foo" and "alias.foo". These config schemes are mis-designed, as the command names can be anything, but the config syntax has some restrictions. For example: $ git foo_bar error: invalid key: pager.foo_bar error: invalid key: alias.foo_bar git: 'foo_bar' is not a git command. See 'git --help'. You cannot name an alias with an underscore. And if you have an external command with one, you cannot configure its pager. In the long run, we may develop a different config scheme for these features. But in the near term (and because we'll need to support the existing scheme indefinitely), we should at least squelch the error messages shown above. These errors come from git_config_parse_key. Ideally we would pass a "quiet" flag to the config machinery, but there are many layers between the pager code and the key parsing. Passing a flag through all of those would be an invasive change. Instead, let's provide a config function to report on whether a key is syntactically valid, and have the pager and alias code skip lookup for bogus keys. We can build this easily around the existing git_config_parse_key, with two minor modifications: 1. We now handle a NULL store_key, to validate but not write out the normalized key. 2. We accept a "quiet" flag to avoid writing to stderr. This doesn't need to be a full-blown public "flags" field, because we can make the existing implementation a static helper function, keeping the mess contained inside config.c. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-08-24 09:11:33 +03:00
if (git_config_key_is_valid(key.buf) &&
!git_config_get_value(key.buf, &value)) {
int b = git_config_maybe_bool(key.buf, value);
if (b >= 0)
want = b;
else {
want = 1;
pager_program = xstrdup(value);
}
}
strbuf_release(&key);
return want;
}