git/usage.c

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/*
* GIT - The information manager from hell
*
* Copyright (C) Linus Torvalds, 2005
*/
#include "git-compat-util.h"
#include "gettext.h"
#include "trace2.h"
static void vreportf(const char *prefix, const char *err, va_list params)
{
char msg[4096];
vreportf(): avoid relying on stdio buffering The MSVC runtime behavior differs from glibc's with respect to `fprintf(stderr, ...)` in that the former writes out the message character by character. In t5516, this leads to a funny problem where a `git fetch` process as well as the `git upload-pack` process spawned by it _both_ call `die()` at the same time. The output can look like this: fatal: git uploadfata-lp: raemcokte :error: upload-pnot our arcef k6: n4ot our ea4cr1e3f 36d45ea94fca1398e86a771eda009872d63adb28598f6a9 8e86a771eda009872d6ab2886 Let's avoid this predicament altogether by rendering the entire message, including the prefix and the trailing newline, into the buffer we already have (and which is still fixed size) and then write it out via `write_in_full()`. We still clip the message to at most 4095 characters. The history of `vreportf()` with regard to this issue includes the following commits: d048a96e (2007-11-09) - 'char msg[256]' is introduced to avoid interleaving 389d1767 (2009-03-25) - Buffer size increased to 1024 to avoid truncation 625a860c (2009-11-22) - Buffer size increased to 4096 to avoid truncation f4c3edc0 (2015-08-11) - Buffer removed to avoid truncation b5a9e435 (2017-01-11) - Reverts f4c3edc0 to be able to replace control chars before sending to stderr 9ac13ec9 (2006-10-11) - Another attempt to solve interleaving. This is seemingly related to d048a96e. 137a0d0e (2007-11-19) - Addresses out-of-order for display() 34df8aba (2009-03-10) - Switches xwrite() to fprintf() in recv_sideband() to support UTF-8 emulation eac14f89 (2012-01-14) - Removes the need for fprintf() for UTF-8 emulation, so it's safe to use xwrite() again 5e5be9e2 (2016-06-28) - recv_sideband() uses xwrite() again Note that we print nothing if the `vsnprintf()` call failed to render the error message; There is little we can do in that case, and it should not happen anyway. The process may have written to `stderr` and there may be something left in the buffer kept in the stdio layer. Call `fflush(stderr)` before writing the message we prepare in this function. Helped-by: Jeff King <peff@peff.net> Helped-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com> Helped-by: SZEDER Gábor <szeder.dev@gmail.com> Helped-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-30 10:44:36 +00:00
char *p, *pend = msg + sizeof(msg);
size_t prefix_len = strlen(prefix);
vreportf(): avoid relying on stdio buffering The MSVC runtime behavior differs from glibc's with respect to `fprintf(stderr, ...)` in that the former writes out the message character by character. In t5516, this leads to a funny problem where a `git fetch` process as well as the `git upload-pack` process spawned by it _both_ call `die()` at the same time. The output can look like this: fatal: git uploadfata-lp: raemcokte :error: upload-pnot our arcef k6: n4ot our ea4cr1e3f 36d45ea94fca1398e86a771eda009872d63adb28598f6a9 8e86a771eda009872d6ab2886 Let's avoid this predicament altogether by rendering the entire message, including the prefix and the trailing newline, into the buffer we already have (and which is still fixed size) and then write it out via `write_in_full()`. We still clip the message to at most 4095 characters. The history of `vreportf()` with regard to this issue includes the following commits: d048a96e (2007-11-09) - 'char msg[256]' is introduced to avoid interleaving 389d1767 (2009-03-25) - Buffer size increased to 1024 to avoid truncation 625a860c (2009-11-22) - Buffer size increased to 4096 to avoid truncation f4c3edc0 (2015-08-11) - Buffer removed to avoid truncation b5a9e435 (2017-01-11) - Reverts f4c3edc0 to be able to replace control chars before sending to stderr 9ac13ec9 (2006-10-11) - Another attempt to solve interleaving. This is seemingly related to d048a96e. 137a0d0e (2007-11-19) - Addresses out-of-order for display() 34df8aba (2009-03-10) - Switches xwrite() to fprintf() in recv_sideband() to support UTF-8 emulation eac14f89 (2012-01-14) - Removes the need for fprintf() for UTF-8 emulation, so it's safe to use xwrite() again 5e5be9e2 (2016-06-28) - recv_sideband() uses xwrite() again Note that we print nothing if the `vsnprintf()` call failed to render the error message; There is little we can do in that case, and it should not happen anyway. The process may have written to `stderr` and there may be something left in the buffer kept in the stdio layer. Call `fflush(stderr)` before writing the message we prepare in this function. Helped-by: Jeff King <peff@peff.net> Helped-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com> Helped-by: SZEDER Gábor <szeder.dev@gmail.com> Helped-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-30 10:44:36 +00:00
if (sizeof(msg) <= prefix_len) {
fprintf(stderr, "BUG!!! too long a prefix '%s'\n", prefix);
abort();
}
memcpy(msg, prefix, prefix_len);
p = msg + prefix_len;
if (vsnprintf(p, pend - p, err, params) < 0) {
fprintf(stderr, _("error: unable to format message: %s\n"),
err);
vreportf(): avoid relying on stdio buffering The MSVC runtime behavior differs from glibc's with respect to `fprintf(stderr, ...)` in that the former writes out the message character by character. In t5516, this leads to a funny problem where a `git fetch` process as well as the `git upload-pack` process spawned by it _both_ call `die()` at the same time. The output can look like this: fatal: git uploadfata-lp: raemcokte :error: upload-pnot our arcef k6: n4ot our ea4cr1e3f 36d45ea94fca1398e86a771eda009872d63adb28598f6a9 8e86a771eda009872d6ab2886 Let's avoid this predicament altogether by rendering the entire message, including the prefix and the trailing newline, into the buffer we already have (and which is still fixed size) and then write it out via `write_in_full()`. We still clip the message to at most 4095 characters. The history of `vreportf()` with regard to this issue includes the following commits: d048a96e (2007-11-09) - 'char msg[256]' is introduced to avoid interleaving 389d1767 (2009-03-25) - Buffer size increased to 1024 to avoid truncation 625a860c (2009-11-22) - Buffer size increased to 4096 to avoid truncation f4c3edc0 (2015-08-11) - Buffer removed to avoid truncation b5a9e435 (2017-01-11) - Reverts f4c3edc0 to be able to replace control chars before sending to stderr 9ac13ec9 (2006-10-11) - Another attempt to solve interleaving. This is seemingly related to d048a96e. 137a0d0e (2007-11-19) - Addresses out-of-order for display() 34df8aba (2009-03-10) - Switches xwrite() to fprintf() in recv_sideband() to support UTF-8 emulation eac14f89 (2012-01-14) - Removes the need for fprintf() for UTF-8 emulation, so it's safe to use xwrite() again 5e5be9e2 (2016-06-28) - recv_sideband() uses xwrite() again Note that we print nothing if the `vsnprintf()` call failed to render the error message; There is little we can do in that case, and it should not happen anyway. The process may have written to `stderr` and there may be something left in the buffer kept in the stdio layer. Call `fflush(stderr)` before writing the message we prepare in this function. Helped-by: Jeff King <peff@peff.net> Helped-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com> Helped-by: SZEDER Gábor <szeder.dev@gmail.com> Helped-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-30 10:44:36 +00:00
*p = '\0'; /* vsnprintf() failed, clip at prefix */
}
vreportf(): avoid relying on stdio buffering The MSVC runtime behavior differs from glibc's with respect to `fprintf(stderr, ...)` in that the former writes out the message character by character. In t5516, this leads to a funny problem where a `git fetch` process as well as the `git upload-pack` process spawned by it _both_ call `die()` at the same time. The output can look like this: fatal: git uploadfata-lp: raemcokte :error: upload-pnot our arcef k6: n4ot our ea4cr1e3f 36d45ea94fca1398e86a771eda009872d63adb28598f6a9 8e86a771eda009872d6ab2886 Let's avoid this predicament altogether by rendering the entire message, including the prefix and the trailing newline, into the buffer we already have (and which is still fixed size) and then write it out via `write_in_full()`. We still clip the message to at most 4095 characters. The history of `vreportf()` with regard to this issue includes the following commits: d048a96e (2007-11-09) - 'char msg[256]' is introduced to avoid interleaving 389d1767 (2009-03-25) - Buffer size increased to 1024 to avoid truncation 625a860c (2009-11-22) - Buffer size increased to 4096 to avoid truncation f4c3edc0 (2015-08-11) - Buffer removed to avoid truncation b5a9e435 (2017-01-11) - Reverts f4c3edc0 to be able to replace control chars before sending to stderr 9ac13ec9 (2006-10-11) - Another attempt to solve interleaving. This is seemingly related to d048a96e. 137a0d0e (2007-11-19) - Addresses out-of-order for display() 34df8aba (2009-03-10) - Switches xwrite() to fprintf() in recv_sideband() to support UTF-8 emulation eac14f89 (2012-01-14) - Removes the need for fprintf() for UTF-8 emulation, so it's safe to use xwrite() again 5e5be9e2 (2016-06-28) - recv_sideband() uses xwrite() again Note that we print nothing if the `vsnprintf()` call failed to render the error message; There is little we can do in that case, and it should not happen anyway. The process may have written to `stderr` and there may be something left in the buffer kept in the stdio layer. Call `fflush(stderr)` before writing the message we prepare in this function. Helped-by: Jeff King <peff@peff.net> Helped-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com> Helped-by: SZEDER Gábor <szeder.dev@gmail.com> Helped-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-30 10:44:36 +00:00
for (; p != pend - 1 && *p; p++) {
if (iscntrl(*p) && *p != '\t' && *p != '\n')
*p = '?';
}
vreportf(): avoid relying on stdio buffering The MSVC runtime behavior differs from glibc's with respect to `fprintf(stderr, ...)` in that the former writes out the message character by character. In t5516, this leads to a funny problem where a `git fetch` process as well as the `git upload-pack` process spawned by it _both_ call `die()` at the same time. The output can look like this: fatal: git uploadfata-lp: raemcokte :error: upload-pnot our arcef k6: n4ot our ea4cr1e3f 36d45ea94fca1398e86a771eda009872d63adb28598f6a9 8e86a771eda009872d6ab2886 Let's avoid this predicament altogether by rendering the entire message, including the prefix and the trailing newline, into the buffer we already have (and which is still fixed size) and then write it out via `write_in_full()`. We still clip the message to at most 4095 characters. The history of `vreportf()` with regard to this issue includes the following commits: d048a96e (2007-11-09) - 'char msg[256]' is introduced to avoid interleaving 389d1767 (2009-03-25) - Buffer size increased to 1024 to avoid truncation 625a860c (2009-11-22) - Buffer size increased to 4096 to avoid truncation f4c3edc0 (2015-08-11) - Buffer removed to avoid truncation b5a9e435 (2017-01-11) - Reverts f4c3edc0 to be able to replace control chars before sending to stderr 9ac13ec9 (2006-10-11) - Another attempt to solve interleaving. This is seemingly related to d048a96e. 137a0d0e (2007-11-19) - Addresses out-of-order for display() 34df8aba (2009-03-10) - Switches xwrite() to fprintf() in recv_sideband() to support UTF-8 emulation eac14f89 (2012-01-14) - Removes the need for fprintf() for UTF-8 emulation, so it's safe to use xwrite() again 5e5be9e2 (2016-06-28) - recv_sideband() uses xwrite() again Note that we print nothing if the `vsnprintf()` call failed to render the error message; There is little we can do in that case, and it should not happen anyway. The process may have written to `stderr` and there may be something left in the buffer kept in the stdio layer. Call `fflush(stderr)` before writing the message we prepare in this function. Helped-by: Jeff King <peff@peff.net> Helped-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com> Helped-by: SZEDER Gábor <szeder.dev@gmail.com> Helped-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-30 10:44:36 +00:00
*(p++) = '\n'; /* we no longer need a NUL */
fflush(stderr);
write_in_full(2, msg, p - msg);
}
static NORETURN void usage_builtin(const char *err, va_list params)
{
vreportf(_("usage: "), err, params);
/*
* When we detect a usage error *before* the command dispatch in
* cmd_main(), we don't know what verb to report. Force it to this
* to facilitate post-processing.
*/
trace2_cmd_name("_usage_");
/*
* Currently, the (err, params) are usually just the static usage
* string which isn't very useful here. Usually, the call site
* manually calls fprintf(stderr,...) with the actual detailed
* syntax error before calling usage().
*
* TODO It would be nice to update the call sites to pass both
* the static usage string and the detailed error message.
*/
exit(129);
}
static void die_message_builtin(const char *err, va_list params)
{
trace2_cmd_error_va(err, params);
vreportf(_("fatal: "), err, params);
}
/*
* We call trace2_cmd_error_va() in the below functions first and
* expect it to va_copy 'params' before using it (because an 'ap' can
* only be walked once).
*/
static NORETURN void die_builtin(const char *err, va_list params)
{
report_fn die_message_fn = get_die_message_routine();
die_message_fn(err, params);
exit(128);
}
static void error_builtin(const char *err, va_list params)
{
trace2_cmd_error_va(err, params);
vreportf(_("error: "), err, params);
}
static void warn_builtin(const char *warn, va_list params)
{
trace2_cmd_error_va(warn, params);
vreportf(_("warning: "), warn, params);
}
static int die_is_recursing_builtin(void)
{
static int dying;
die(): stop hiding errors due to overzealous recursion guard Change the recursion limit for the default die routine from a *very* low 1 to 1024. This ensures that infinite recursions are broken, but doesn't lose the meaningful error messages under threaded execution where threads concurrently start to die. The intent of the existing code, as explained in commit cd163d4b4e ("usage.c: detect recursion in die routines and bail out immediately", 2012-11-14), is to break infinite recursion in cases where the die routine itself calls die(), and would thus infinitely recurse. However, doing that very aggressively by immediately printing out "recursion detected in die handler" if we've already called die() once means that threaded invocations of git can end up only printing out the "recursion detected" error, while hiding the meaningful error. An example of this is running a threaded grep which dies on execution against pretty much any repo, git.git will do: git grep -P --threads=8 '(*LIMIT_MATCH=1)-?-?-?---$' With the current version of git this will print some combination of multiple PCRE failures that caused the abort and multiple "recursion detected", some invocations will print out multiple "recursion detected" errors with no PCRE error at all! Before this change, running the above grep command 1000 times against git.git[1] and taking the top 20 results will on my system yield the following distribution of actual errors ("E") and recursion errors ("R"): 322 E R 306 E 116 E R R 65 R R 54 R E 49 E E 44 R 15 E R R R 9 R R R 7 R E R 5 R R E 3 E R R R R 2 E E R 1 R R R R 1 R R R E 1 R E R R The exact results are obviously random and system-dependent, but this shows the race condition in this code. Some small part of the time we're about to print out the actual error ("E") but another thread's recursion error beats us to it, and sometimes we print out nothing but the recursion error. With this change we get, now with "W" to mean the new warning being emitted indicating that we've called die() many times: 502 E 160 E W E 120 E E 53 E W 35 E W E E 34 W E E 29 W E E E 16 E E W 16 E E E 11 W E E E E 7 E E W E 4 W E 3 W W E E 2 E W E E E 1 W W E 1 W E W E 1 E W W E E E 1 E W W E E 1 E W W E 1 E W E E W Which still sucks a bit, due to a still present race-condition in this code we're sometimes going to print out several errors still, or several warnings, or two duplicate errors without the warning. But we will never have a case where we completely hide the actual error as we do now. Now, git-grep could make use of the pluggable error facility added in commit c19a490e37 ("usage: allow pluggable die-recursion checks", 2013-04-16). There's other threaded code that calls set_die_routine() or set_die_is_recursing_routine(). But this is about fixing the general die() behavior with threading when we don't have such a custom routine yet. Right now the common case is not an infinite recursion in the handler, but us losing error messages by default because we're overly paranoid about our recursion check. So let's just set the recursion limit to a number higher than the number of threads we're ever likely to spawn. Now we won't lose errors, and if we have a recursing die handler we'll still die within microseconds. There are race conditions in this code itself, in particular the "dying" variable is not thread mutexed, so we e.g. won't be dying at exactly 1024, or for that matter even be able to accurately test "dying == 2", see the cases where we print out more than one "W" above. But that doesn't really matter, for the recursion guard we just need to die "soon", not at exactly 1024 calls, and for printing the correct error and only one warning most of the time in the face of threaded death this is good enough and a net improvement on the current code. 1. for i in {1..1000}; do git grep -P --threads=8 '(*LIMIT_MATCH=1)-?-?-?---$' 2>&1|perl -pe 's/^fatal: r.*/R/; s/^fatal: p.*/E/; s/^warning.*/W/' | tr '\n' ' '; echo; done | sort | uniq -c | sort -nr | head -n 20 Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-21 20:47:42 +00:00
/*
* Just an arbitrary number X where "a < x < b" where "a" is
* "maximum number of pthreads we'll ever plausibly spawn" and
* "b" is "something less than Inf", since the point is to
* prevent infinite recursion.
*/
static const int recursion_limit = 1024;
dying++;
if (dying > recursion_limit) {
return 1;
} else if (dying == 2) {
warning("die() called many times. Recursion error or racy threaded death!");
return 0;
} else {
return 0;
}
}
/* If we are in a dlopen()ed .so write to a global variable would segfault
* (ugh), so keep things static. */
static NORETURN_PTR report_fn usage_routine = usage_builtin;
static NORETURN_PTR report_fn die_routine = die_builtin;
static report_fn die_message_routine = die_message_builtin;
static report_fn error_routine = error_builtin;
static report_fn warn_routine = warn_builtin;
static int (*die_is_recursing)(void) = die_is_recursing_builtin;
void set_die_routine(NORETURN_PTR report_fn routine)
{
die_routine = routine;
}
report_fn get_die_message_routine(void)
{
return die_message_routine;
}
void set_error_routine(report_fn routine)
{
error_routine = routine;
}
report_fn get_error_routine(void)
{
return error_routine;
}
void set_warn_routine(report_fn routine)
{
warn_routine = routine;
}
report_fn get_warn_routine(void)
{
return warn_routine;
}
void set_die_is_recursing_routine(int (*routine)(void))
{
die_is_recursing = routine;
}
Fix sparse warnings Fix warnings from 'make check'. - These files don't include 'builtin.h' causing sparse to complain that cmd_* isn't declared: builtin/clone.c:364, builtin/fetch-pack.c:797, builtin/fmt-merge-msg.c:34, builtin/hash-object.c:78, builtin/merge-index.c:69, builtin/merge-recursive.c:22 builtin/merge-tree.c:341, builtin/mktag.c:156, builtin/notes.c:426 builtin/notes.c:822, builtin/pack-redundant.c:596, builtin/pack-refs.c:10, builtin/patch-id.c:60, builtin/patch-id.c:149, builtin/remote.c:1512, builtin/remote-ext.c:240, builtin/remote-fd.c:53, builtin/reset.c:236, builtin/send-pack.c:384, builtin/unpack-file.c:25, builtin/var.c:75 - These files have symbols which should be marked static since they're only file scope: submodule.c:12, diff.c:631, replace_object.c:92, submodule.c:13, submodule.c:14, trace.c:78, transport.c:195, transport-helper.c:79, unpack-trees.c:19, url.c:3, url.c:18, url.c:104, url.c:117, url.c:123, url.c:129, url.c:136, thread-utils.c:21, thread-utils.c:48 - These files redeclare symbols to be different types: builtin/index-pack.c:210, parse-options.c:564, parse-options.c:571, usage.c:49, usage.c:58, usage.c:63, usage.c:72 - These files use a literal integer 0 when they really should use a NULL pointer: daemon.c:663, fast-import.c:2942, imap-send.c:1072, notes-merge.c:362 While we're in the area, clean up some unused #includes in builtin files (mostly exec_cmd.h). Signed-off-by: Stephen Boyd <bebarino@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-03-22 07:51:05 +00:00
void NORETURN usagef(const char *err, ...)
{
va_list params;
va_start(params, err);
usage_routine(err, params);
va_end(params);
}
Fix sparse warnings Fix warnings from 'make check'. - These files don't include 'builtin.h' causing sparse to complain that cmd_* isn't declared: builtin/clone.c:364, builtin/fetch-pack.c:797, builtin/fmt-merge-msg.c:34, builtin/hash-object.c:78, builtin/merge-index.c:69, builtin/merge-recursive.c:22 builtin/merge-tree.c:341, builtin/mktag.c:156, builtin/notes.c:426 builtin/notes.c:822, builtin/pack-redundant.c:596, builtin/pack-refs.c:10, builtin/patch-id.c:60, builtin/patch-id.c:149, builtin/remote.c:1512, builtin/remote-ext.c:240, builtin/remote-fd.c:53, builtin/reset.c:236, builtin/send-pack.c:384, builtin/unpack-file.c:25, builtin/var.c:75 - These files have symbols which should be marked static since they're only file scope: submodule.c:12, diff.c:631, replace_object.c:92, submodule.c:13, submodule.c:14, trace.c:78, transport.c:195, transport-helper.c:79, unpack-trees.c:19, url.c:3, url.c:18, url.c:104, url.c:117, url.c:123, url.c:129, url.c:136, thread-utils.c:21, thread-utils.c:48 - These files redeclare symbols to be different types: builtin/index-pack.c:210, parse-options.c:564, parse-options.c:571, usage.c:49, usage.c:58, usage.c:63, usage.c:72 - These files use a literal integer 0 when they really should use a NULL pointer: daemon.c:663, fast-import.c:2942, imap-send.c:1072, notes-merge.c:362 While we're in the area, clean up some unused #includes in builtin files (mostly exec_cmd.h). Signed-off-by: Stephen Boyd <bebarino@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-03-22 07:51:05 +00:00
void NORETURN usage(const char *err)
{
usagef("%s", err);
}
Fix sparse warnings Fix warnings from 'make check'. - These files don't include 'builtin.h' causing sparse to complain that cmd_* isn't declared: builtin/clone.c:364, builtin/fetch-pack.c:797, builtin/fmt-merge-msg.c:34, builtin/hash-object.c:78, builtin/merge-index.c:69, builtin/merge-recursive.c:22 builtin/merge-tree.c:341, builtin/mktag.c:156, builtin/notes.c:426 builtin/notes.c:822, builtin/pack-redundant.c:596, builtin/pack-refs.c:10, builtin/patch-id.c:60, builtin/patch-id.c:149, builtin/remote.c:1512, builtin/remote-ext.c:240, builtin/remote-fd.c:53, builtin/reset.c:236, builtin/send-pack.c:384, builtin/unpack-file.c:25, builtin/var.c:75 - These files have symbols which should be marked static since they're only file scope: submodule.c:12, diff.c:631, replace_object.c:92, submodule.c:13, submodule.c:14, trace.c:78, transport.c:195, transport-helper.c:79, unpack-trees.c:19, url.c:3, url.c:18, url.c:104, url.c:117, url.c:123, url.c:129, url.c:136, thread-utils.c:21, thread-utils.c:48 - These files redeclare symbols to be different types: builtin/index-pack.c:210, parse-options.c:564, parse-options.c:571, usage.c:49, usage.c:58, usage.c:63, usage.c:72 - These files use a literal integer 0 when they really should use a NULL pointer: daemon.c:663, fast-import.c:2942, imap-send.c:1072, notes-merge.c:362 While we're in the area, clean up some unused #includes in builtin files (mostly exec_cmd.h). Signed-off-by: Stephen Boyd <bebarino@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-03-22 07:51:05 +00:00
void NORETURN die(const char *err, ...)
{
va_list params;
if (die_is_recursing()) {
fputs("fatal: recursion detected in die handler\n", stderr);
exit(128);
}
va_start(params, err);
die_routine(err, params);
va_end(params);
}
static const char *fmt_with_err(char *buf, int n, const char *fmt)
{
char str_error[256], *err;
int i, j;
err = strerror(errno);
for (i = j = 0; err[i] && j < sizeof(str_error) - 1; ) {
if ((str_error[j++] = err[i++]) != '%')
continue;
if (j < sizeof(str_error) - 1) {
str_error[j++] = '%';
} else {
/* No room to double the '%', so we overwrite it with
* '\0' below */
j--;
break;
}
}
str_error[j] = 0;
/* Truncation is acceptable here */
snprintf(buf, n, "%s: %s", fmt, str_error);
return buf;
}
void NORETURN die_errno(const char *fmt, ...)
{
char buf[1024];
va_list params;
if (die_is_recursing()) {
fputs("fatal: recursion detected in die_errno handler\n",
stderr);
exit(128);
}
va_start(params, fmt);
die_routine(fmt_with_err(buf, sizeof(buf), fmt), params);
va_end(params);
}
#undef die_message
int die_message(const char *err, ...)
{
va_list params;
va_start(params, err);
die_message_routine(err, params);
va_end(params);
return 128;
}
#undef die_message_errno
int die_message_errno(const char *fmt, ...)
{
char buf[1024];
va_list params;
va_start(params, fmt);
die_message_routine(fmt_with_err(buf, sizeof(buf), fmt), params);
va_end(params);
return 128;
}
#undef error_errno
int error_errno(const char *fmt, ...)
{
char buf[1024];
va_list params;
va_start(params, fmt);
error_routine(fmt_with_err(buf, sizeof(buf), fmt), params);
va_end(params);
return -1;
}
make error()'s constant return value more visible When git is compiled with "gcc -Wuninitialized -O3", some inlined calls provide an additional opportunity for the compiler to do static analysis on variable initialization. For example, with two functions like this: int get_foo(int *foo) { if (something_that_might_fail() < 0) return error("unable to get foo"); *foo = 0; return 0; } void some_fun(void) { int foo; if (get_foo(&foo) < 0) return -1; printf("foo is %d\n", foo); } If get_foo() is not inlined, then when compiling some_fun, gcc sees only that a pointer to the local variable is passed, and must assume that it is an out parameter that is initialized after get_foo returns. However, when get_foo() is inlined, the compiler may look at all of the code together and see that some code paths in get_foo() do not initialize the variable. As a result, it prints a warning. But what the compiler can't see is that error() always returns -1, and therefore we know that either we return early from some_fun, or foo ends up initialized, and the code is safe. The warning is a false positive. If we can make the compiler aware that error() will always return -1, it can do a better job of analysis. The simplest method would be to inline the error() function. However, this doesn't work, because gcc will not inline a variadc function. We can work around this by defining a macro. This relies on two gcc extensions: 1. Variadic macros (these are present in C99, but we do not rely on that). 2. Gcc treats the "##" paste operator specially between a comma and __VA_ARGS__, which lets our variadic macro work even if no format parameters are passed to error(). Since we are using these extra features, we hide the macro behind an #ifdef. This is OK, though, because our goal was just to help gcc. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2012-12-15 17:37:36 +00:00
#undef error
int error(const char *err, ...)
{
va_list params;
va_start(params, err);
error_routine(err, params);
va_end(params);
return -1;
}
void warning_errno(const char *warn, ...)
{
char buf[1024];
va_list params;
va_start(params, warn);
warn_routine(fmt_with_err(buf, sizeof(buf), warn), params);
va_end(params);
}
void warning(const char *warn, ...)
{
va_list params;
va_start(params, warn);
warn_routine(warn, params);
va_end(params);
}
usage.c: add BUG() function There's a convention in Git's code base to write assertions as: if (...some_bad_thing...) die("BUG: the terrible thing happened"); with the idea that users should never see a "BUG:" message (but if they, it at least gives a clue what happened). We use die() here because it's convenient, but there are a few draw-backs: 1. Without parsing the messages, it's hard for callers to distinguish BUG assertions from regular errors. For instance, it would be nice if the test suite could check that we don't hit any assertions, but test_must_fail will pass BUG deaths as OK. 2. It would be useful to add more debugging features to BUG assertions, like file/line numbers or dumping core. 3. The die() handler can be replaced, and might not actually exit the whole program (e.g., it may just pthread_exit()). This is convenient for normal errors, but for an assertion failure (which is supposed to never happen), we're probably better off taking down the whole process as quickly and cleanly as possible. We could address these by checking in die() whether the error message starts with "BUG", and behaving appropriately. But there's little advantage at that point to sharing the die() code, and only downsides (e.g., we can't change the BUG() interface independently). Moreover, converting all of the existing BUG calls reveals that the test suite does indeed trigger a few of them. Instead, this patch introduces a new BUG() function, which prints an error before dying via SIGABRT. This gives us test suite checking and core dumps. The function is actually a macro (when supported) so that we can show the file/line number. We can convert die("BUG") invocations to BUG() in further patches, dealing with any test fallouts individually. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-13 03:28:50 +00:00
/* Only set this, ever, from t/helper/, when verifying that bugs are caught. */
int BUG_exit_code;
static void BUG_vfl_common(const char *file, int line, const char *fmt,
va_list params)
usage.c: add BUG() function There's a convention in Git's code base to write assertions as: if (...some_bad_thing...) die("BUG: the terrible thing happened"); with the idea that users should never see a "BUG:" message (but if they, it at least gives a clue what happened). We use die() here because it's convenient, but there are a few draw-backs: 1. Without parsing the messages, it's hard for callers to distinguish BUG assertions from regular errors. For instance, it would be nice if the test suite could check that we don't hit any assertions, but test_must_fail will pass BUG deaths as OK. 2. It would be useful to add more debugging features to BUG assertions, like file/line numbers or dumping core. 3. The die() handler can be replaced, and might not actually exit the whole program (e.g., it may just pthread_exit()). This is convenient for normal errors, but for an assertion failure (which is supposed to never happen), we're probably better off taking down the whole process as quickly and cleanly as possible. We could address these by checking in die() whether the error message starts with "BUG", and behaving appropriately. But there's little advantage at that point to sharing the die() code, and only downsides (e.g., we can't change the BUG() interface independently). Moreover, converting all of the existing BUG calls reveals that the test suite does indeed trigger a few of them. Instead, this patch introduces a new BUG() function, which prints an error before dying via SIGABRT. This gives us test suite checking and core dumps. The function is actually a macro (when supported) so that we can show the file/line number. We can convert die("BUG") invocations to BUG() in further patches, dealing with any test fallouts individually. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-13 03:28:50 +00:00
{
char prefix[256];
/* truncation via snprintf is OK here */
C99: remove hardcoded-out !HAVE_VARIADIC_MACROS code Remove the "else" branches of the HAVE_VARIADIC_MACROS macro, which have been unconditionally omitted since 765dc168882 (git-compat-util: always enable variadic macros, 2021-01-28). Since were always omitted, anyone trying to use a compiler without variadic macro support to compile a git since version git v2.31.0 or later would have had a compilation error. 10 months across a few releases since then should have been enough time for anyone who cared to run into that and report the issue. In addition to that, for anyone unsetting HAVE_VARIADIC_MACROS we've been emitting extremely verbose warnings since at least ee4512ed481 (trace2: create new combined trace facility, 2019-02-22). That's because there is no such thing as a "region_enter_printf" or "region_leave_printf" format, so at least under GCC and Clang everything that includes trace.h (almost every file) emits a couple of warnings about that. There's a large benefit to being able to have a hard dependency rely on variadic macros, the code surrounding usage.c is hard to maintain if we need to write two implementations of everything, and by relying on "__FILE__" and "__LINE__" along with "__VA_ARGS__" we can in the future make error(), die() etc. log where they were called from. We've also recently merged d67fc4bf0ba (Merge branch 'bc/require-c99', 2021-12-10) which further cements our hard dependency on C99. So let's delete the fallback code, and update our CodingGuidelines to note that we depend on this. The added bullet-point starts with lower-case for consistency with other bullet-points in that section. The diff in "trace.h" is relatively hard to read, since we need to retain the existing API docs, which were comments on the code used if HAVE_VARIADIC_MACROS was not defined. Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-02-21 16:05:27 +00:00
snprintf(prefix, sizeof(prefix), "BUG: %s:%d: ", file, line);
usage.c: add BUG() function There's a convention in Git's code base to write assertions as: if (...some_bad_thing...) die("BUG: the terrible thing happened"); with the idea that users should never see a "BUG:" message (but if they, it at least gives a clue what happened). We use die() here because it's convenient, but there are a few draw-backs: 1. Without parsing the messages, it's hard for callers to distinguish BUG assertions from regular errors. For instance, it would be nice if the test suite could check that we don't hit any assertions, but test_must_fail will pass BUG deaths as OK. 2. It would be useful to add more debugging features to BUG assertions, like file/line numbers or dumping core. 3. The die() handler can be replaced, and might not actually exit the whole program (e.g., it may just pthread_exit()). This is convenient for normal errors, but for an assertion failure (which is supposed to never happen), we're probably better off taking down the whole process as quickly and cleanly as possible. We could address these by checking in die() whether the error message starts with "BUG", and behaving appropriately. But there's little advantage at that point to sharing the die() code, and only downsides (e.g., we can't change the BUG() interface independently). Moreover, converting all of the existing BUG calls reveals that the test suite does indeed trigger a few of them. Instead, this patch introduces a new BUG() function, which prints an error before dying via SIGABRT. This gives us test suite checking and core dumps. The function is actually a macro (when supported) so that we can show the file/line number. We can convert die("BUG") invocations to BUG() in further patches, dealing with any test fallouts individually. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-13 03:28:50 +00:00
vreportf(prefix, fmt, params);
}
static NORETURN void BUG_vfl(const char *file, int line, const char *fmt, va_list params)
{
va_list params_copy;
static int in_bug;
va_copy(params_copy, params);
BUG_vfl_common(file, line, fmt, params);
if (in_bug)
abort();
in_bug = 1;
trace2_cmd_error_va(fmt, params_copy);
if (BUG_exit_code)
exit(BUG_exit_code);
usage.c: add BUG() function There's a convention in Git's code base to write assertions as: if (...some_bad_thing...) die("BUG: the terrible thing happened"); with the idea that users should never see a "BUG:" message (but if they, it at least gives a clue what happened). We use die() here because it's convenient, but there are a few draw-backs: 1. Without parsing the messages, it's hard for callers to distinguish BUG assertions from regular errors. For instance, it would be nice if the test suite could check that we don't hit any assertions, but test_must_fail will pass BUG deaths as OK. 2. It would be useful to add more debugging features to BUG assertions, like file/line numbers or dumping core. 3. The die() handler can be replaced, and might not actually exit the whole program (e.g., it may just pthread_exit()). This is convenient for normal errors, but for an assertion failure (which is supposed to never happen), we're probably better off taking down the whole process as quickly and cleanly as possible. We could address these by checking in die() whether the error message starts with "BUG", and behaving appropriately. But there's little advantage at that point to sharing the die() code, and only downsides (e.g., we can't change the BUG() interface independently). Moreover, converting all of the existing BUG calls reveals that the test suite does indeed trigger a few of them. Instead, this patch introduces a new BUG() function, which prints an error before dying via SIGABRT. This gives us test suite checking and core dumps. The function is actually a macro (when supported) so that we can show the file/line number. We can convert die("BUG") invocations to BUG() in further patches, dealing with any test fallouts individually. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-13 03:28:50 +00:00
abort();
}
NORETURN void BUG_fl(const char *file, int line, const char *fmt, ...)
usage.c: add BUG() function There's a convention in Git's code base to write assertions as: if (...some_bad_thing...) die("BUG: the terrible thing happened"); with the idea that users should never see a "BUG:" message (but if they, it at least gives a clue what happened). We use die() here because it's convenient, but there are a few draw-backs: 1. Without parsing the messages, it's hard for callers to distinguish BUG assertions from regular errors. For instance, it would be nice if the test suite could check that we don't hit any assertions, but test_must_fail will pass BUG deaths as OK. 2. It would be useful to add more debugging features to BUG assertions, like file/line numbers or dumping core. 3. The die() handler can be replaced, and might not actually exit the whole program (e.g., it may just pthread_exit()). This is convenient for normal errors, but for an assertion failure (which is supposed to never happen), we're probably better off taking down the whole process as quickly and cleanly as possible. We could address these by checking in die() whether the error message starts with "BUG", and behaving appropriately. But there's little advantage at that point to sharing the die() code, and only downsides (e.g., we can't change the BUG() interface independently). Moreover, converting all of the existing BUG calls reveals that the test suite does indeed trigger a few of them. Instead, this patch introduces a new BUG() function, which prints an error before dying via SIGABRT. This gives us test suite checking and core dumps. The function is actually a macro (when supported) so that we can show the file/line number. We can convert die("BUG") invocations to BUG() in further patches, dealing with any test fallouts individually. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-13 03:28:50 +00:00
{
va_list ap;
bug_called_must_BUG = 0;
usage.c: add BUG() function There's a convention in Git's code base to write assertions as: if (...some_bad_thing...) die("BUG: the terrible thing happened"); with the idea that users should never see a "BUG:" message (but if they, it at least gives a clue what happened). We use die() here because it's convenient, but there are a few draw-backs: 1. Without parsing the messages, it's hard for callers to distinguish BUG assertions from regular errors. For instance, it would be nice if the test suite could check that we don't hit any assertions, but test_must_fail will pass BUG deaths as OK. 2. It would be useful to add more debugging features to BUG assertions, like file/line numbers or dumping core. 3. The die() handler can be replaced, and might not actually exit the whole program (e.g., it may just pthread_exit()). This is convenient for normal errors, but for an assertion failure (which is supposed to never happen), we're probably better off taking down the whole process as quickly and cleanly as possible. We could address these by checking in die() whether the error message starts with "BUG", and behaving appropriately. But there's little advantage at that point to sharing the die() code, and only downsides (e.g., we can't change the BUG() interface independently). Moreover, converting all of the existing BUG calls reveals that the test suite does indeed trigger a few of them. Instead, this patch introduces a new BUG() function, which prints an error before dying via SIGABRT. This gives us test suite checking and core dumps. The function is actually a macro (when supported) so that we can show the file/line number. We can convert die("BUG") invocations to BUG() in further patches, dealing with any test fallouts individually. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-05-13 03:28:50 +00:00
va_start(ap, fmt);
BUG_vfl(file, line, fmt, ap);
va_end(ap);
}
add UNLEAK annotation for reducing leak false positives 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>
2017-09-08 06:38:41 +00:00
int bug_called_must_BUG;
void bug_fl(const char *file, int line, const char *fmt, ...)
{
va_list ap;
bug_called_must_BUG = 1;
va_start(ap, fmt);
BUG_vfl_common(file, line, fmt, ap);
va_end(ap);
va_start(ap, fmt);
trace2_cmd_error_va(fmt, ap);
va_end(ap);
}
add UNLEAK annotation for reducing leak false positives 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>
2017-09-08 06:38:41 +00:00
#ifdef SUPPRESS_ANNOTATED_LEAKS
void unleak_memory(const void *ptr, size_t len)
{
static struct suppressed_leak_root {
struct suppressed_leak_root *next;
char data[FLEX_ARRAY];
} *suppressed_leaks;
struct suppressed_leak_root *root;
FLEX_ALLOC_MEM(root, data, ptr, len);
root->next = suppressed_leaks;
suppressed_leaks = root;
}
#endif