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git/trace.h

279 lines
8.1 KiB

#ifndef TRACE_H
#define TRACE_H
#include "git-compat-util.h"
#include "strbuf.h"
/**
* The trace API can be used to print debug messages to stderr or a file. Trace
* code is inactive unless explicitly enabled by setting `GIT_TRACE*` environment
* variables.
*
* The trace implementation automatically adds `timestamp file:line ... \n` to
* all trace messages. E.g.:
*
* ------------
* 23:59:59.123456 git.c:312 trace: built-in: git 'foo'
* 00:00:00.000001 builtin/foo.c:99 foo: some message
* ------------
*
* Bugs & Caveats
* --------------
*
* GIT_TRACE_* environment variables can be used to tell Git to show
* trace output to its standard error stream. Git can often spawn a pager
* internally to run its subcommand and send its standard output and
* standard error to it.
*
* Because GIT_TRACE_PERFORMANCE trace is generated only at the very end
* of the program with atexit(), which happens after the pager exits, it
* would not work well if you send its log to the standard error output
* and let Git spawn the pager at the same time.
*
* As a work around, you can for example use '--no-pager', or set
* GIT_TRACE_PERFORMANCE to another file descriptor which is redirected
* to stderr, or set GIT_TRACE_PERFORMANCE to a file specified by its
* absolute path.
*
* For example instead of the following command which by default may not
* print any performance information:
*
* ------------
* GIT_TRACE_PERFORMANCE=2 git log -1
* ------------
*
* you may want to use:
*
* ------------
* GIT_TRACE_PERFORMANCE=2 git --no-pager log -1
* ------------
*
* or:
*
* ------------
* GIT_TRACE_PERFORMANCE=3 3>&2 git log -1
* ------------
*
* or:
*
* ------------
* GIT_TRACE_PERFORMANCE=/path/to/log/file git log -1
* ------------
*
*/
/**
* Defines a trace key (or category). The default (for API functions that
* don't take a key) is `GIT_TRACE`.
*
* E.g. to define a trace key controlled by environment variable `GIT_TRACE_FOO`:
*
* ------------
* static struct trace_key trace_foo = TRACE_KEY_INIT(FOO);
*
* static void trace_print_foo(const char *message)
* {
* trace_printf_key(&trace_foo, "%s", message);
* }
* ------------
*
* Note: don't use `const` as the trace implementation stores internal state in
* the `trace_key` structure.
*/
struct trace_key {
const char * const key;
int fd;
unsigned int initialized : 1;
unsigned int need_close : 1;
};
extern struct trace_key trace_default_key;
#define TRACE_KEY_INIT(name) { .key = "GIT_TRACE_" #name }
extern struct trace_key trace_perf_key;
extern struct trace_key trace_setup_key;
void trace_repo_setup(const char *prefix);
/**
* Checks whether the trace key is enabled. Used to prevent expensive
* string formatting before calling one of the printing APIs.
*/
int trace_want(struct trace_key *key);
/**
* Enables or disables tracing for the specified key, as if the environment
* variable was set to the given value.
*/
void trace_override_envvar(struct trace_key *key, const char *value);
/**
* Disables tracing for the specified key, even if the environment variable
* was set.
*/
void trace_disable(struct trace_key *key);
/**
* Returns nanoseconds since the epoch (01/01/1970), typically used
* for performance measurements.
* Currently there are high precision timer implementations for Linux (using
* `clock_gettime(CLOCK_MONOTONIC)`) and Windows (`QueryPerformanceCounter`).
* Other platforms use `gettimeofday` as time source.
*/
uint64_t getnanotime(void);
void trace_command_performance(const char **argv);
void trace_verbatim(struct trace_key *key, const void *buf, unsigned len);
uint64_t trace_performance_enter(void);
/*
* TRACE_CONTEXT may be set to __FUNCTION__ if the compiler supports it. The
* default is __FILE__, as it is consistent with assert(), and static function
* names are not necessarily unique.
*
* __FILE__ ":" __FUNCTION__ doesn't work with GNUC, as __FILE__ is supplied
* by the preprocessor as a string literal, and __FUNCTION__ is filled in by
* the compiler as a string constant.
*/
#ifndef TRACE_CONTEXT
# define TRACE_CONTEXT __FILE__
#endif
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>
7 months ago
/**
* Macros to add the file:line of the calling code, instead of that of
* the trace function itself.
*
* Note: with C99 variadic macros, __VA_ARGS__ must include the last fixed
* parameter ('format' in this case). Otherwise, a call without variable
* arguments will have a surplus ','. E.g.:
*
* #define foo(format, ...) bar(format, __VA_ARGS__)
* foo("test");
*
* will expand to
*
* bar("test",);
*
* which is invalid (note the ',)'). With GNUC, '##__VA_ARGS__' drops the
* comma, but this is non-standard.
*/
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>
7 months ago
/**
* trace_printf(), accepts "const char *format, ...".
*
* Prints a formatted message, similar to printf.
*/
#define trace_printf(...) trace_printf_key(&trace_default_key, __VA_ARGS__)
/**
* trace_printf_key(), accepts "struct trace_key *key, const char *format, ...".
*/
#define trace_printf_key(key, ...) \
do { \
if (trace_pass_fl(key)) \
trace_printf_key_fl(TRACE_CONTEXT, __LINE__, key, \
__VA_ARGS__); \
} while (0)
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>
7 months ago
/**
* trace_argv_printf(), accepts "struct trace_key *key, const char *format, ...)".
*
* Prints a formatted message, followed by a quoted list of arguments.
*/
#define trace_argv_printf(argv, ...) \
do { \
if (trace_pass_fl(&trace_default_key)) \
trace_argv_printf_fl(TRACE_CONTEXT, __LINE__, \
argv, __VA_ARGS__); \
} while (0)
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>
7 months ago
/**
* trace_strbuf(), accepts "struct trace_key *key, const struct strbuf *data".
*
* Prints the strbuf, without additional formatting (i.e. doesn't
* choke on `%` or even `\0`).
*/
#define trace_strbuf(key, data) \
do { \
if (trace_pass_fl(key)) \
trace_strbuf_fl(TRACE_CONTEXT, __LINE__, key, data);\
} while (0)
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>
7 months ago
/**
* trace_performance(), accepts "uint64_t nanos, const char *format, ...".
*
* Prints elapsed time (in nanoseconds) if GIT_TRACE_PERFORMANCE is enabled.
*
* Example:
* ------------
* uint64_t t = 0;
* for (;;) {
* // ignore
* t -= getnanotime();
* // code section to measure
* t += getnanotime();
* // ignore
* }
* trace_performance(t, "frotz");
* ------------
*/
#define trace_performance(nanos, ...) \
do { \
if (trace_pass_fl(&trace_perf_key)) \
trace_performance_fl(TRACE_CONTEXT, __LINE__, nanos,\
__VA_ARGS__); \
} while (0)
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>
7 months ago
/**
* trace_performance_since(), accepts "uint64_t start, const char *format, ...".
*
* Prints elapsed time since 'start' if GIT_TRACE_PERFORMANCE is enabled.
*
* Example:
* ------------
* uint64_t start = getnanotime();
* // code section to measure
* trace_performance_since(start, "foobar");
* ------------
*/
#define trace_performance_since(start, ...) \
do { \
if (trace_pass_fl(&trace_perf_key)) \
trace_performance_fl(TRACE_CONTEXT, __LINE__, \
getnanotime() - (start), \
__VA_ARGS__); \
} while (0)
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>
7 months ago
/**
* trace_performance_leave(), accepts "const char *format, ...".
*/
#define trace_performance_leave(...) \
do { \
if (trace_pass_fl(&trace_perf_key)) \
trace_performance_leave_fl(TRACE_CONTEXT, __LINE__, \
getnanotime(), \
__VA_ARGS__); \
} while (0)
/* backend functions, use non-*fl macros instead */
__attribute__((format (printf, 4, 5)))
void trace_printf_key_fl(const char *file, int line, struct trace_key *key,
const char *format, ...);
__attribute__((format (printf, 4, 5)))
void trace_argv_printf_fl(const char *file, int line, const char **argv,
const char *format, ...);
void trace_strbuf_fl(const char *file, int line, struct trace_key *key,
const struct strbuf *data);
__attribute__((format (printf, 4, 5)))
void trace_performance_fl(const char *file, int line,
uint64_t nanos, const char *fmt, ...);
__attribute__((format (printf, 4, 5)))
void trace_performance_leave_fl(const char *file, int line,
uint64_t nanos, const char *fmt, ...);
static inline int trace_pass_fl(struct trace_key *key)
{
return key->fd || !key->initialized;
}
#endif /* TRACE_H */