[thirdparty/git.git] / trace.h

#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

/**
 * 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.
 */

/**
 * 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)

/**
 * 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)

/**
 * 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)

/**
 * 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)

/**
 * 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)

/**
 * 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 */
Commit	Line	Data
5991a55c KB	1	#ifndef TRACE_H
	2	#define TRACE_H
	3
	4	#include "git-compat-util.h"
	5	#include "strbuf.h"
	6
f1ecbe0f HW	7	/**
	8	* The trace API can be used to print debug messages to stderr or a file. Trace
	9	* code is inactive unless explicitly enabled by setting `GIT_TRACE*` environment
	10	* variables.
	11	*
	12	* The trace implementation automatically adds `timestamp file:line ... \n` to
	13	* all trace messages. E.g.:
	14	*
	15	* ------------
	16	* 23:59:59.123456 git.c:312 trace: built-in: git 'foo'
	17	* 00:00:00.000001 builtin/foo.c:99 foo: some message
	18	* ------------
	19	*
	20	* Bugs & Caveats
	21	* --------------
	22	*
	23	* GIT_TRACE_* environment variables can be used to tell Git to show
	24	* trace output to its standard error stream. Git can often spawn a pager
	25	* internally to run its subcommand and send its standard output and
	26	* standard error to it.
	27	*
	28	* Because GIT_TRACE_PERFORMANCE trace is generated only at the very end
	29	* of the program with atexit(), which happens after the pager exits, it
	30	* would not work well if you send its log to the standard error output
	31	* and let Git spawn the pager at the same time.
	32	*
	33	* As a work around, you can for example use '--no-pager', or set
	34	* GIT_TRACE_PERFORMANCE to another file descriptor which is redirected
	35	* to stderr, or set GIT_TRACE_PERFORMANCE to a file specified by its
	36	* absolute path.
	37	*
	38	* For example instead of the following command which by default may not
	39	* print any performance information:
	40	*
	41	* ------------
	42	* GIT_TRACE_PERFORMANCE=2 git log -1
	43	* ------------
	44	*
	45	* you may want to use:
	46	*
	47	* ------------
	48	* GIT_TRACE_PERFORMANCE=2 git --no-pager log -1
	49	* ------------
	50	*
	51	* or:
	52	*
	53	* ------------
	54	* GIT_TRACE_PERFORMANCE=3 3>&2 git log -1
	55	* ------------
	56	*
	57	* or:
	58	*
	59	* ------------
	60	* GIT_TRACE_PERFORMANCE=/path/to/log/file git log -1
	61	* ------------
	62	*
	63	*/
	64
	65	/**
	66	* Defines a trace key (or category). The default (for API functions that
	67	* don't take a key) is `GIT_TRACE`.
	68	*
	69	* E.g. to define a trace key controlled by environment variable `GIT_TRACE_FOO`:
	70	*
71	* ------------
72	* static struct trace_key trace_foo = TRACE_KEY_INIT(FOO);
73	*
74	* static void trace_print_foo(const char *message)
75	* {
76	* trace_printf_key(&trace_foo, "%s", message);
77	* }
78	* ------------
79	*
80	* Note: don't use `const` as the trace implementation stores internal state in
81	* the `trace_key` structure.
82	*/
6aa30857 KB	83	struct trace_key {
	84	const char * const key;
	85	int fd;
	86	unsigned int initialized : 1;
	87	unsigned int need_close : 1;
	88	};
	89
406102a7 GK	90	extern struct trace_key trace_default_key;
406102a7 GK	91
f69a6e4f	92	#define TRACE_KEY_INIT(name) { .key = "GIT_TRACE_" #name }
8eeb25c6	93	extern struct trace_key trace_perf_key;
cb507619	94	extern struct trace_key trace_setup_key;
6aa30857	95
55454427	96	void trace_repo_setup(const char *prefix);
f1ecbe0f HW	97
	98	/**
	99	* Checks whether the trace key is enabled. Used to prevent expensive
	100	* string formatting before calling one of the printing APIs.
	101	*/
55454427	102	int trace_want(struct trace_key *key);
f1ecbe0f	103
7167a62b JT	104	/**
	105	* Enables or disables tracing for the specified key, as if the environment
	106	* variable was set to the given value.
	107	*/
	108	void trace_override_envvar(struct trace_key key, const char value);
	109
f1ecbe0f HW	110	/**
	111	* Disables tracing for the specified key, even if the environment variable
	112	* was set.
	113	*/
55454427	114	void trace_disable(struct trace_key *key);
f1ecbe0f HW	115
	116	/**
	117	* Returns nanoseconds since the epoch (01/01/1970), typically used
	118	* for performance measurements.
	119	* Currently there are high precision timer implementations for Linux (using
	120	* `clock_gettime(CLOCK_MONOTONIC)`) and Windows (`QueryPerformanceCounter`).
	121	* Other platforms use `gettimeofday` as time source.
	122	*/
55454427	123	uint64_t getnanotime(void);
f1ecbe0f	124
55454427 DL	125	void trace_command_performance(const char **argv);
55454427 DL	126	void trace_verbatim(struct trace_key key, const void buf, unsigned len);
c46c406a	127	uint64_t trace_performance_enter(void);
66f66c59	128
e05bed96 KB	129	/*
	130	* TRACE_CONTEXT may be set to __FUNCTION__ if the compiler supports it. The
	131	* default is __FILE__, as it is consistent with assert(), and static function
	132	* names are not necessarily unique.
	133	*
	134	* __FILE__ ":" __FUNCTION__ doesn't work with GNUC, as __FILE__ is supplied
	135	* by the preprocessor as a string literal, and __FUNCTION__ is filled in by
	136	* the compiler as a string constant.
	137	*/
	138	#ifndef TRACE_CONTEXT
	139	# define TRACE_CONTEXT __FILE__
	140	#endif
	141
56a29d2c ÆAB	142	/**
	143	* Macros to add the file:line of the calling code, instead of that of
	144	* the trace function itself.
	145	*
e05bed96 KB	146	* Note: with C99 variadic macros, __VA_ARGS__ must include the last fixed
	147	* parameter ('format' in this case). Otherwise, a call without variable
	148	* arguments will have a surplus ','. E.g.:
	149	*
	150	* #define foo(format, ...) bar(format, __VA_ARGS__)
	151	* foo("test");
	152	*
	153	* will expand to
	154	*
	155	* bar("test",);
	156	*
	157	* which is invalid (note the ',)'). With GNUC, '##__VA_ARGS__' drops the
	158	* comma, but this is non-standard.
	159	*/
	160
56a29d2c ÆAB	161	/**
	162	* trace_printf(), accepts "const char *format, ...".
	163	*
	164	* Prints a formatted message, similar to printf.
	165	*/
	166	#define trace_printf(...) trace_printf_key(&trace_default_key, __VA_ARGS__)
	167
	168	/**
	169	* trace_printf_key(), accepts "struct trace_key key, const char format, ...".
	170	*/
8eeb25c6 GK	171	#define trace_printf_key(key, ...) \
	172	do { \
	173	if (trace_pass_fl(key)) \
	174	trace_printf_key_fl(TRACE_CONTEXT, __LINE__, key, \
	175	__VA_ARGS__); \
	176	} while (0)
	177
56a29d2c ÆAB	178	/**
	179	* trace_argv_printf(), accepts "struct trace_key key, const char format, ...)".
	180	*
	181	* Prints a formatted message, followed by a quoted list of arguments.
	182	*/
8eeb25c6 GK	183	#define trace_argv_printf(argv, ...) \
	184	do { \
	185	if (trace_pass_fl(&trace_default_key)) \
	186	trace_argv_printf_fl(TRACE_CONTEXT, __LINE__, \
	187	argv, __VA_ARGS__); \
	188	} while (0)
	189
56a29d2c ÆAB	190	/**
	191	* trace_strbuf(), accepts "struct trace_key key, const struct strbuf data".
	192	*
	193	* Prints the strbuf, without additional formatting (i.e. doesn't
	194	* choke on `%` or even `\0`).
	195	*/
8eeb25c6 GK	196	#define trace_strbuf(key, data) \
	197	do { \
	198	if (trace_pass_fl(key)) \
	199	trace_strbuf_fl(TRACE_CONTEXT, __LINE__, key, data);\
	200	} while (0)
	201
56a29d2c ÆAB	202	/**
	203	* trace_performance(), accepts "uint64_t nanos, const char *format, ...".
	204	*
	205	* Prints elapsed time (in nanoseconds) if GIT_TRACE_PERFORMANCE is enabled.
	206	*
	207	* Example:
	208	* ------------
	209	* uint64_t t = 0;
	210	* for (;;) {
	211	* // ignore
	212	* t -= getnanotime();
	213	* // code section to measure
	214	* t += getnanotime();
	215	* // ignore
	216	* }
	217	* trace_performance(t, "frotz");
	218	* ------------
	219	*/
8eeb25c6 GK	220	#define trace_performance(nanos, ...) \
	221	do { \
	222	if (trace_pass_fl(&trace_perf_key)) \
	223	trace_performance_fl(TRACE_CONTEXT, __LINE__, nanos,\
	224	__VA_ARGS__); \
	225	} while (0)
	226
56a29d2c ÆAB	227	/**
	228	* trace_performance_since(), accepts "uint64_t start, const char *format, ...".
	229	*
	230	* Prints elapsed time since 'start' if GIT_TRACE_PERFORMANCE is enabled.
	231	*
	232	* Example:
	233	* ------------
	234	* uint64_t start = getnanotime();
	235	* // code section to measure
	236	* trace_performance_since(start, "foobar");
	237	* ------------
	238	*/
8eeb25c6 GK	239	#define trace_performance_since(start, ...) \
	240	do { \
	241	if (trace_pass_fl(&trace_perf_key)) \
	242	trace_performance_fl(TRACE_CONTEXT, __LINE__, \
	243	getnanotime() - (start), \
	244	__VA_ARGS__); \
	245	} while (0)
09b2c1c7	246
56a29d2c ÆAB	247	/**
	248	* trace_performance_leave(), accepts "const char *format, ...".
	249	*/
c46c406a NTND	250	#define trace_performance_leave(...) \
	251	do { \
	252	if (trace_pass_fl(&trace_perf_key)) \
	253	trace_performance_leave_fl(TRACE_CONTEXT, __LINE__, \
	254	getnanotime(), \
	255	__VA_ARGS__); \
	256	} while (0)
	257
e05bed96 KB	258	/* backend functions, use non-fl macros instead /
e05bed96 KB	259	__attribute__((format (printf, 4, 5)))
b199d714	260	void trace_printf_key_fl(const char file, int line, struct trace_key key,
ad6dad09	261	const char *format, ...);
e05bed96	262	__attribute__((format (printf, 4, 5)))
b199d714	263	void trace_argv_printf_fl(const char file, int line, const char *argv,
ad6dad09	264	const char *format, ...);
55454427	265	void trace_strbuf_fl(const char file, int line, struct trace_key key,
ad6dad09	266	const struct strbuf *data);
09b2c1c7	267	__attribute__((format (printf, 4, 5)))
b199d714	268	void trace_performance_fl(const char *file, int line,
ad6dad09	269	uint64_t nanos, const char *fmt, ...);
c46c406a	270	__attribute__((format (printf, 4, 5)))
b199d714	271	void trace_performance_leave_fl(const char *file, int line,
ad6dad09	272	uint64_t nanos, const char *fmt, ...);
8eeb25c6 GK	273	static inline int trace_pass_fl(struct trace_key *key)
	274	{
	275	return key->fd \|\| !key->initialized;
	276	}
e05bed96	277
5991a55c	278	#endif /* TRACE_H */