Fourth batch
[git.git] / trace.h
blob0dbbad0e41cb074e669f58fc3ed347e16faeb45c
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 * Enables or disables tracing for the specified key, as if the environment
106 * variable was set to the given value.
108 void trace_override_envvar(struct trace_key *key, const char *value);
111 * Disables tracing for the specified key, even if the environment variable
112 * was set.
114 void trace_disable(struct trace_key *key);
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.
123 uint64_t getnanotime(void);
125 void trace_command_performance(const char **argv);
126 void trace_verbatim(struct trace_key *key, const void *buf, unsigned len);
127 uint64_t trace_performance_enter(void);
129 #ifndef HAVE_VARIADIC_MACROS
132 * Prints a formatted message, similar to printf.
134 __attribute__((format (printf, 1, 2)))
135 void trace_printf(const char *format, ...);
137 __attribute__((format (printf, 2, 3)))
138 void trace_printf_key(struct trace_key *key, const char *format, ...);
141 * Prints a formatted message, followed by a quoted list of arguments.
143 __attribute__((format (printf, 2, 3)))
144 void trace_argv_printf(const char **argv, const char *format, ...);
147 * Prints the strbuf, without additional formatting (i.e. doesn't
148 * choke on `%` or even `\0`).
150 void trace_strbuf(struct trace_key *key, const struct strbuf *data);
153 * Prints elapsed time (in nanoseconds) if GIT_TRACE_PERFORMANCE is enabled.
155 * Example:
156 * ------------
157 * uint64_t t = 0;
158 * for (;;) {
159 * // ignore
160 * t -= getnanotime();
161 * // code section to measure
162 * t += getnanotime();
163 * // ignore
165 * trace_performance(t, "frotz");
166 * ------------
168 __attribute__((format (printf, 2, 3)))
169 void trace_performance(uint64_t nanos, const char *format, ...);
172 * Prints elapsed time since 'start' if GIT_TRACE_PERFORMANCE is enabled.
174 * Example:
175 * ------------
176 * uint64_t start = getnanotime();
177 * // code section to measure
178 * trace_performance_since(start, "foobar");
179 * ------------
181 __attribute__((format (printf, 2, 3)))
182 void trace_performance_since(uint64_t start, const char *format, ...);
184 __attribute__((format (printf, 1, 2)))
185 void trace_performance_leave(const char *format, ...);
187 #else
190 * Macros to add file:line - see above for C-style declarations of how these
191 * should be used.
195 * TRACE_CONTEXT may be set to __FUNCTION__ if the compiler supports it. The
196 * default is __FILE__, as it is consistent with assert(), and static function
197 * names are not necessarily unique.
199 * __FILE__ ":" __FUNCTION__ doesn't work with GNUC, as __FILE__ is supplied
200 * by the preprocessor as a string literal, and __FUNCTION__ is filled in by
201 * the compiler as a string constant.
203 #ifndef TRACE_CONTEXT
204 # define TRACE_CONTEXT __FILE__
205 #endif
208 * Note: with C99 variadic macros, __VA_ARGS__ must include the last fixed
209 * parameter ('format' in this case). Otherwise, a call without variable
210 * arguments will have a surplus ','. E.g.:
212 * #define foo(format, ...) bar(format, __VA_ARGS__)
213 * foo("test");
215 * will expand to
217 * bar("test",);
219 * which is invalid (note the ',)'). With GNUC, '##__VA_ARGS__' drops the
220 * comma, but this is non-standard.
223 #define trace_printf_key(key, ...) \
224 do { \
225 if (trace_pass_fl(key)) \
226 trace_printf_key_fl(TRACE_CONTEXT, __LINE__, key, \
227 __VA_ARGS__); \
228 } while (0)
230 #define trace_printf(...) trace_printf_key(&trace_default_key, __VA_ARGS__)
232 #define trace_argv_printf(argv, ...) \
233 do { \
234 if (trace_pass_fl(&trace_default_key)) \
235 trace_argv_printf_fl(TRACE_CONTEXT, __LINE__, \
236 argv, __VA_ARGS__); \
237 } while (0)
239 #define trace_strbuf(key, data) \
240 do { \
241 if (trace_pass_fl(key)) \
242 trace_strbuf_fl(TRACE_CONTEXT, __LINE__, key, data);\
243 } while (0)
245 #define trace_performance(nanos, ...) \
246 do { \
247 if (trace_pass_fl(&trace_perf_key)) \
248 trace_performance_fl(TRACE_CONTEXT, __LINE__, nanos,\
249 __VA_ARGS__); \
250 } while (0)
252 #define trace_performance_since(start, ...) \
253 do { \
254 if (trace_pass_fl(&trace_perf_key)) \
255 trace_performance_fl(TRACE_CONTEXT, __LINE__, \
256 getnanotime() - (start), \
257 __VA_ARGS__); \
258 } while (0)
260 #define trace_performance_leave(...) \
261 do { \
262 if (trace_pass_fl(&trace_perf_key)) \
263 trace_performance_leave_fl(TRACE_CONTEXT, __LINE__, \
264 getnanotime(), \
265 __VA_ARGS__); \
266 } while (0)
268 /* backend functions, use non-*fl macros instead */
269 __attribute__((format (printf, 4, 5)))
270 void trace_printf_key_fl(const char *file, int line, struct trace_key *key,
271 const char *format, ...);
272 __attribute__((format (printf, 4, 5)))
273 void trace_argv_printf_fl(const char *file, int line, const char **argv,
274 const char *format, ...);
275 void trace_strbuf_fl(const char *file, int line, struct trace_key *key,
276 const struct strbuf *data);
277 __attribute__((format (printf, 4, 5)))
278 void trace_performance_fl(const char *file, int line,
279 uint64_t nanos, const char *fmt, ...);
280 __attribute__((format (printf, 4, 5)))
281 void trace_performance_leave_fl(const char *file, int line,
282 uint64_t nanos, const char *fmt, ...);
283 static inline int trace_pass_fl(struct trace_key *key)
285 return key->fd || !key->initialized;
288 #endif /* HAVE_VARIADIC_MACROS */
290 #endif /* TRACE_H */