diff options
Diffstat (limited to 'trace.h')
| -rw-r--r-- | trace.h | 200 |
1 files changed, 161 insertions, 39 deletions
@@ -1,9 +1,84 @@ #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; @@ -13,49 +88,43 @@ struct trace_key { extern struct trace_key trace_default_key; -#define TRACE_KEY_INIT(name) { "GIT_TRACE_" #name, 0, 0, 0 } +#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); +void trace_repo_setup(void); + +/** + * 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); -#ifndef HAVE_VARIADIC_MACROS - -__attribute__((format (printf, 1, 2))) -void trace_printf(const char *format, ...); - -__attribute__((format (printf, 2, 3))) -void trace_printf_key(struct trace_key *key, const char *format, ...); - -__attribute__((format (printf, 2, 3))) -void trace_argv_printf(const char **argv, const char *format, ...); - -void trace_strbuf(struct trace_key *key, const struct strbuf *data); - -/* Prints elapsed time (in nanoseconds) if GIT_TRACE_PERFORMANCE is enabled. */ -__attribute__((format (printf, 2, 3))) -void trace_performance(uint64_t nanos, const char *format, ...); - -/* Prints elapsed time since 'start' if GIT_TRACE_PERFORMANCE is enabled. */ -__attribute__((format (printf, 2, 3))) -void trace_performance_since(uint64_t start, const char *format, ...); - -__attribute__((format (printf, 1, 2))) -void trace_performance_leave(const char *format, ...); - -#else - -/* - * Macros to add file:line - see above for C-style declarations of how these - * should be used. - */ - /* * 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 @@ -69,7 +138,10 @@ void trace_performance_leave(const char *format, ...); # 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.: @@ -85,6 +157,16 @@ void trace_performance_leave(const char *format, ...); * 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)) \ @@ -92,8 +174,11 @@ void trace_performance_leave(const char *format, ...); __VA_ARGS__); \ } while (0) -#define trace_printf(...) trace_printf_key(&trace_default_key, __VA_ARGS__) - +/** + * 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)) \ @@ -101,12 +186,36 @@ void trace_performance_leave(const char *format, ...); 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)) \ @@ -114,6 +223,18 @@ void trace_performance_leave(const char *format, ...); __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)) \ @@ -122,6 +243,9 @@ void trace_performance_leave(const char *format, ...); __VA_ARGS__); \ } while (0) +/** + * trace_performance_leave(), accepts "const char *format, ...". + */ #define trace_performance_leave(...) \ do { \ if (trace_pass_fl(&trace_perf_key)) \ @@ -150,6 +274,4 @@ static inline int trace_pass_fl(struct trace_key *key) return key->fd || !key->initialized; } -#endif /* HAVE_VARIADIC_MACROS */ - #endif /* TRACE_H */ |