/src/git/trace.h

Source
#ifndef TRACE_H
#define TRACE_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;

struct repository;

void trace_repo_setup(struct repository *r);

/**
 * 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 */

Coverage Report

Created: 2025-12-31 07:02

Line	Count	Source
1		#ifndef TRACE_H
2		#define TRACE_H
3
4		#include "strbuf.h"
5
6		/**
7		* The trace API can be used to print debug messages to stderr or a file. Trace
8		* code is inactive unless explicitly enabled by setting `GIT_TRACE*` environment
9		* variables.
10		*
11		* The trace implementation automatically adds `timestamp file:line ... \n` to
12		* all trace messages. E.g.:
13		*
14		* ------------
15		* 23:59:59.123456 git.c:312 trace: built-in: git 'foo'
16		* 00:00:00.000001 builtin/foo.c:99 foo: some message
17		* ------------
18		*
19		* Bugs & Caveats
20		* --------------
21		*
22		* GIT_TRACE_* environment variables can be used to tell Git to show
23		* trace output to its standard error stream. Git can often spawn a pager
24		* internally to run its subcommand and send its standard output and
25		* standard error to it.
26		*
27		* Because GIT_TRACE_PERFORMANCE trace is generated only at the very end
28		* of the program with atexit(), which happens after the pager exits, it
29		* would not work well if you send its log to the standard error output
30		* and let Git spawn the pager at the same time.
31		*
32		* As a work around, you can for example use '--no-pager', or set
33		* GIT_TRACE_PERFORMANCE to another file descriptor which is redirected
34		* to stderr, or set GIT_TRACE_PERFORMANCE to a file specified by its
35		* absolute path.
36		*
37		* For example instead of the following command which by default may not
38		* print any performance information:
39		*
40		* ------------
41		* GIT_TRACE_PERFORMANCE=2 git log -1
42		* ------------
43		*
44		* you may want to use:
45		*
46		* ------------
47		* GIT_TRACE_PERFORMANCE=2 git --no-pager log -1
48		* ------------
49		*
50		* or:
51		*
52		* ------------
53		* GIT_TRACE_PERFORMANCE=3 3>&2 git log -1
54		* ------------
55		*
56		* or:
57		*
58		* ------------
59		* GIT_TRACE_PERFORMANCE=/path/to/log/file git log -1
60		* ------------
61		*
62		*/
63
64		/**
65		* Defines a trace key (or category). The default (for API functions that
66		* don't take a key) is `GIT_TRACE`.
67		*
68		* E.g. to define a trace key controlled by environment variable `GIT_TRACE_FOO`:
69		*
70		* ------------
71		* static struct trace_key trace_foo = TRACE_KEY_INIT(FOO);
72		*
73		* static void trace_print_foo(const char *message)
74		* {
75		* trace_printf_key(&trace_foo, "%s", message);
76		* }
77		* ------------
78		*
79		* Note: don't use `const` as the trace implementation stores internal state in
80		* the `trace_key` structure.
81		*/
82		struct trace_key {
83		const char * const key;
84		int fd;
85		unsigned int initialized : 1;
86		unsigned int need_close : 1;
87		};
88
89		extern struct trace_key trace_default_key;
90
91	0	#define TRACE_KEY_INIT(name) { .key = "GIT_TRACE_" #name }
92		extern struct trace_key trace_perf_key;
93		extern struct trace_key trace_setup_key;
94
95		struct repository;
96
97		void trace_repo_setup(struct repository *r);
98
99		/**
100		* Checks whether the trace key is enabled. Used to prevent expensive
101		* string formatting before calling one of the printing APIs.
102		*/
103		int trace_want(struct trace_key *key);
104
105		/**
106		* Enables or disables tracing for the specified key, as if the environment
107		* variable was set to the given value.
108		*/
109		void trace_override_envvar(struct trace_key key, const char value);
110
111		/**
112		* Disables tracing for the specified key, even if the environment variable
113		* was set.
114		*/
115		void trace_disable(struct trace_key *key);
116
117		/**
118		* Returns nanoseconds since the epoch (01/01/1970), typically used
119		* for performance measurements.
120		* Currently there are high precision timer implementations for Linux (using
121		* `clock_gettime(CLOCK_MONOTONIC)`) and Windows (`QueryPerformanceCounter`).
122		* Other platforms use `gettimeofday` as time source.
123		*/
124		uint64_t getnanotime(void);
125
126		void trace_command_performance(const char **argv);
127		void trace_verbatim(struct trace_key key, const void buf, unsigned len);
128		uint64_t trace_performance_enter(void);
129
130		/*
131		* TRACE_CONTEXT may be set to __FUNCTION__ if the compiler supports it. The
132		* default is __FILE__, as it is consistent with assert(), and static function
133		* names are not necessarily unique.
134		*
135		* __FILE__ ":" __FUNCTION__ doesn't work with GNUC, as __FILE__ is supplied
136		* by the preprocessor as a string literal, and __FUNCTION__ is filled in by
137		* the compiler as a string constant.
138		*/
139		#ifndef TRACE_CONTEXT
140	0	# define TRACE_CONTEXT __FILE__
141		#endif
142
143		/**
144		* Macros to add the file:line of the calling code, instead of that of
145		* the trace function itself.
146		*
147		* Note: with C99 variadic macros, __VA_ARGS__ must include the last fixed
148		* parameter ('format' in this case). Otherwise, a call without variable
149		* arguments will have a surplus ','. E.g.:
150		*
151		* #define foo(format, ...) bar(format, __VA_ARGS__)
152		* foo("test");
153		*
154		* will expand to
155		*
156		* bar("test",);
157		*
158		* which is invalid (note the ',)'). With GNUC, '##__VA_ARGS__' drops the
159		* comma, but this is non-standard.
160		*/
161
162		/**
163		* trace_printf(), accepts "const char *format, ...".
164		*
165		* Prints a formatted message, similar to printf.
166		*/
167	0	#define trace_printf(...) trace_printf_key(&trace_default_key, __VA_ARGS__)
168
169		/**
170		* trace_printf_key(), accepts "struct trace_key key, const char format, ...".
171		*/
172		#define trace_printf_key(key, ...) \
173	0	do { \
174	0	if (trace_pass_fl(key)) \
175	0	trace_printf_key_fl(TRACE_CONTEXT, __LINE__, key, \
176	0	__VA_ARGS__); \
177	0	} while (0)
178
179		/**
180		* trace_argv_printf(), accepts "struct trace_key key, const char format, ...)".
181		*
182		* Prints a formatted message, followed by a quoted list of arguments.
183		*/
184		#define trace_argv_printf(argv, ...) \
185	0	do { \
186	0	if (trace_pass_fl(&trace_default_key)) \
187	0	trace_argv_printf_fl(TRACE_CONTEXT, __LINE__, \
188	0	argv, __VA_ARGS__); \
189	0	} while (0)
190
191		/**
192		* trace_strbuf(), accepts "struct trace_key key, const struct strbuf data".
193		*
194		* Prints the strbuf, without additional formatting (i.e. doesn't
195		* choke on `%` or even `\0`).
196		*/
197		#define trace_strbuf(key, data) \
198	0	do { \
199	0	if (trace_pass_fl(key)) \
200	0	trace_strbuf_fl(TRACE_CONTEXT, __LINE__, key, data);\
201	0	} while (0)
202
203		/**
204		* trace_performance(), accepts "uint64_t nanos, const char *format, ...".
205		*
206		* Prints elapsed time (in nanoseconds) if GIT_TRACE_PERFORMANCE is enabled.
207		*
208		* Example:
209		* ------------
210		* uint64_t t = 0;
211		* for (;;) {
212		* // ignore
213		* t -= getnanotime();
214		* // code section to measure
215		* t += getnanotime();
216		* // ignore
217		* }
218		* trace_performance(t, "frotz");
219		* ------------
220		*/
221		#define trace_performance(nanos, ...) \
222		do { \
223		if (trace_pass_fl(&trace_perf_key)) \
224		trace_performance_fl(TRACE_CONTEXT, __LINE__, nanos,\
225		__VA_ARGS__); \
226		} while (0)
227
228		/**
229		* trace_performance_since(), accepts "uint64_t start, const char *format, ...".
230		*
231		* Prints elapsed time since 'start' if GIT_TRACE_PERFORMANCE is enabled.
232		*
233		* Example:
234		* ------------
235		* uint64_t start = getnanotime();
236		* // code section to measure
237		* trace_performance_since(start, "foobar");
238		* ------------
239		*/
240		#define trace_performance_since(start, ...) \
241	0	do { \
242	0	if (trace_pass_fl(&trace_perf_key)) \
243	0	trace_performance_fl(TRACE_CONTEXT, __LINE__, \
244	0	getnanotime() - (start), \
245	0	__VA_ARGS__); \
246	0	} while (0)
247
248		/**
249		* trace_performance_leave(), accepts "const char *format, ...".
250		*/
251		#define trace_performance_leave(...) \
252	0	do { \
253	0	if (trace_pass_fl(&trace_perf_key)) \
254	0	trace_performance_leave_fl(TRACE_CONTEXT, __LINE__, \
255	0	getnanotime(), \
256	0	__VA_ARGS__); \
257	0	} while (0)
258
259		/* backend functions, use non-fl macros instead /
260		__attribute__((format (printf, 4, 5)))
261		void trace_printf_key_fl(const char file, int line, struct trace_key key,
262		const char *format, ...);
263		__attribute__((format (printf, 4, 5)))
264		void trace_argv_printf_fl(const char file, int line, const char *argv,
265		const char *format, ...);
266		void trace_strbuf_fl(const char file, int line, struct trace_key key,
267		const struct strbuf *data);
268		__attribute__((format (printf, 4, 5)))
269		void trace_performance_fl(const char *file, int line,
270		uint64_t nanos, const char *fmt, ...);
271		__attribute__((format (printf, 4, 5)))
272		void trace_performance_leave_fl(const char *file, int line,
273		uint64_t nanos, const char *fmt, ...);
274		static inline int trace_pass_fl(struct trace_key *key)
275	0	{
276	0	return key->fd \|\| !key->initialized;
277	0	} Unexecuted instantiation: run-command.c:trace_pass_fl Unexecuted instantiation: trace.c:trace_pass_fl Unexecuted instantiation: trace2.c:trace_pass_fl Unexecuted instantiation: tr2_tls.c:trace_pass_fl Unexecuted instantiation: tr2_tmr.c:trace_pass_fl Unexecuted instantiation: exec-cmd.c:trace_pass_fl Unexecuted instantiation: fsmonitor.c:trace_pass_fl Unexecuted instantiation: name-hash.c:trace_pass_fl Unexecuted instantiation: packfile.c:trace_pass_fl Unexecuted instantiation: read-cache.c:trace_pass_fl Unexecuted instantiation: debug.c:trace_pass_fl Unexecuted instantiation: setup.c:trace_pass_fl Unexecuted instantiation: shallow.c:trace_pass_fl Unexecuted instantiation: wt-status.c:trace_pass_fl Unexecuted instantiation: cache-tree.c:trace_pass_fl Unexecuted instantiation: chdir-notify.c:trace_pass_fl Unexecuted instantiation: convert.c:trace_pass_fl Unexecuted instantiation: diff-lib.c:trace_pass_fl Unexecuted instantiation: list-objects-filter-options.c:trace_pass_fl Unexecuted instantiation: list-objects.c:trace_pass_fl Unexecuted instantiation: pkt-line.c:trace_pass_fl Unexecuted instantiation: preload-index.c:trace_pass_fl Unexecuted instantiation: progress.c:trace_pass_fl Unexecuted instantiation: unpack-trees.c:trace_pass_fl Unexecuted instantiation: entry.c:trace_pass_fl
278
279		#endif /* TRACE_H */