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[git.git] / trace.h
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1 #ifndef TRACE_H
2 #define TRACE_H
4 #include "git-compat-util.h"
5 #include "strbuf.h"
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.
12 * The trace implementation automatically adds `timestamp file:line ... \n` to
13 * all trace messages. E.g.:
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 * ------------
20 * Bugs & Caveats
21 * --------------
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.
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.
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.
38 * For example instead of the following command which by default may not
39 * print any performance information:
41 * ------------
42 * GIT_TRACE_PERFORMANCE=2 git log -1
43 * ------------
45 * you may want to use:
47 * ------------
48 * GIT_TRACE_PERFORMANCE=2 git --no-pager log -1
49 * ------------
51 * or:
53 * ------------
54 * GIT_TRACE_PERFORMANCE=3 3>&2 git log -1
55 * ------------
57 * or:
59 * ------------
60 * GIT_TRACE_PERFORMANCE=/path/to/log/file git log -1
61 * ------------
65 /**
66 * Defines a trace key (or category). The default (for API functions that
67 * don't take a key) is `GIT_TRACE`.
69 * E.g. to define a trace key controlled by environment variable `GIT_TRACE_FOO`:
71 * ------------
72 * static struct trace_key trace_foo = TRACE_KEY_INIT(FOO);
74 * static void trace_print_foo(const char *message)
75 * {
76 * trace_printf_key(&trace_foo, "%s", message);
77 * }
78 * ------------
80 * Note: don't use `const` as the trace implementation stores internal state in
81 * the `trace_key` structure.
83 struct trace_key {
84 const char * const key;
85 int fd;
86 unsigned int initialized : 1;
87 unsigned int need_close : 1;
90 extern struct trace_key trace_default_key;
92 #define TRACE_KEY_INIT(name) { "GIT_TRACE_" #name, 0, 0, 0 }
93 extern struct trace_key trace_perf_key;
94 extern struct trace_key trace_setup_key;
96 void trace_repo_setup(const char *prefix);
98 /**
99 * Checks whether the trace key is enabled. Used to prevent expensive
100 * string formatting before calling one of the printing APIs.
102 int trace_want(struct trace_key *key);
105 * Disables tracing for the specified key, even if the environment variable
106 * was set.
108 void trace_disable(struct trace_key *key);
111 * Returns nanoseconds since the epoch (01/01/1970), typically used
112 * for performance measurements.
113 * Currently there are high precision timer implementations for Linux (using
114 * `clock_gettime(CLOCK_MONOTONIC)`) and Windows (`QueryPerformanceCounter`).
115 * Other platforms use `gettimeofday` as time source.
117 uint64_t getnanotime(void);
119 void trace_command_performance(const char **argv);
120 void trace_verbatim(struct trace_key *key, const void *buf, unsigned len);
121 uint64_t trace_performance_enter(void);
123 #ifndef HAVE_VARIADIC_MACROS
126 * Prints a formatted message, similar to printf.
128 __attribute__((format (printf, 1, 2)))
129 void trace_printf(const char *format, ...);
131 __attribute__((format (printf, 2, 3)))
132 void trace_printf_key(struct trace_key *key, const char *format, ...);
135 * Prints a formatted message, followed by a quoted list of arguments.
137 __attribute__((format (printf, 2, 3)))
138 void trace_argv_printf(const char **argv, const char *format, ...);
141 * Prints the strbuf, without additional formatting (i.e. doesn't
142 * choke on `%` or even `\0`).
144 void trace_strbuf(struct trace_key *key, const struct strbuf *data);
147 * Prints elapsed time (in nanoseconds) if GIT_TRACE_PERFORMANCE is enabled.
149 * Example:
150 * ------------
151 * uint64_t t = 0;
152 * for (;;) {
153 * // ignore
154 * t -= getnanotime();
155 * // code section to measure
156 * t += getnanotime();
157 * // ignore
159 * trace_performance(t, "frotz");
160 * ------------
162 __attribute__((format (printf, 2, 3)))
163 void trace_performance(uint64_t nanos, const char *format, ...);
166 * Prints elapsed time since 'start' if GIT_TRACE_PERFORMANCE is enabled.
168 * Example:
169 * ------------
170 * uint64_t start = getnanotime();
171 * // code section to measure
172 * trace_performance_since(start, "foobar");
173 * ------------
175 __attribute__((format (printf, 2, 3)))
176 void trace_performance_since(uint64_t start, const char *format, ...);
178 __attribute__((format (printf, 1, 2)))
179 void trace_performance_leave(const char *format, ...);
181 #else
184 * Macros to add file:line - see above for C-style declarations of how these
185 * should be used.
189 * TRACE_CONTEXT may be set to __FUNCTION__ if the compiler supports it. The
190 * default is __FILE__, as it is consistent with assert(), and static function
191 * names are not necessarily unique.
193 * __FILE__ ":" __FUNCTION__ doesn't work with GNUC, as __FILE__ is supplied
194 * by the preprocessor as a string literal, and __FUNCTION__ is filled in by
195 * the compiler as a string constant.
197 #ifndef TRACE_CONTEXT
198 # define TRACE_CONTEXT __FILE__
199 #endif
202 * Note: with C99 variadic macros, __VA_ARGS__ must include the last fixed
203 * parameter ('format' in this case). Otherwise, a call without variable
204 * arguments will have a surplus ','. E.g.:
206 * #define foo(format, ...) bar(format, __VA_ARGS__)
207 * foo("test");
209 * will expand to
211 * bar("test",);
213 * which is invalid (note the ',)'). With GNUC, '##__VA_ARGS__' drops the
214 * comma, but this is non-standard.
217 #define trace_printf_key(key, ...) \
218 do { \
219 if (trace_pass_fl(key)) \
220 trace_printf_key_fl(TRACE_CONTEXT, __LINE__, key, \
221 __VA_ARGS__); \
222 } while (0)
224 #define trace_printf(...) trace_printf_key(&trace_default_key, __VA_ARGS__)
226 #define trace_argv_printf(argv, ...) \
227 do { \
228 if (trace_pass_fl(&trace_default_key)) \
229 trace_argv_printf_fl(TRACE_CONTEXT, __LINE__, \
230 argv, __VA_ARGS__); \
231 } while (0)
233 #define trace_strbuf(key, data) \
234 do { \
235 if (trace_pass_fl(key)) \
236 trace_strbuf_fl(TRACE_CONTEXT, __LINE__, key, data);\
237 } while (0)
239 #define trace_performance(nanos, ...) \
240 do { \
241 if (trace_pass_fl(&trace_perf_key)) \
242 trace_performance_fl(TRACE_CONTEXT, __LINE__, nanos,\
243 __VA_ARGS__); \
244 } while (0)
246 #define trace_performance_since(start, ...) \
247 do { \
248 if (trace_pass_fl(&trace_perf_key)) \
249 trace_performance_fl(TRACE_CONTEXT, __LINE__, \
250 getnanotime() - (start), \
251 __VA_ARGS__); \
252 } while (0)
254 #define trace_performance_leave(...) \
255 do { \
256 if (trace_pass_fl(&trace_perf_key)) \
257 trace_performance_leave_fl(TRACE_CONTEXT, __LINE__, \
258 getnanotime(), \
259 __VA_ARGS__); \
260 } while (0)
262 /* backend functions, use non-*fl macros instead */
263 __attribute__((format (printf, 4, 5)))
264 void trace_printf_key_fl(const char *file, int line, struct trace_key *key,
265 const char *format, ...);
266 __attribute__((format (printf, 4, 5)))
267 void trace_argv_printf_fl(const char *file, int line, const char **argv,
268 const char *format, ...);
269 void trace_strbuf_fl(const char *file, int line, struct trace_key *key,
270 const struct strbuf *data);
271 __attribute__((format (printf, 4, 5)))
272 void trace_performance_fl(const char *file, int line,
273 uint64_t nanos, const char *fmt, ...);
274 __attribute__((format (printf, 4, 5)))
275 void trace_performance_leave_fl(const char *file, int line,
276 uint64_t nanos, const char *fmt, ...);
277 static inline int trace_pass_fl(struct trace_key *key)
279 return key->fd || !key->initialized;
282 #endif /* HAVE_VARIADIC_MACROS */
284 #endif /* TRACE_H */