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git/trace.h

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C
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#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) { "GIT_TRACE_" #name, 0, 0, 0 }
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);
#ifndef HAVE_VARIADIC_MACROS
/**
* Prints a formatted message, similar to printf.
*/
__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, ...);
/**
* Prints a formatted message, followed by a quoted list of arguments.
*/
__attribute__((format (printf, 2, 3)))
void trace_argv_printf(const char **argv, const char *format, ...);
/**
* Prints the strbuf, without additional formatting (i.e. doesn't
* choke on `%` or even `\0`).
*/
void trace_strbuf(struct trace_key *key, const struct strbuf *data);
/**
* 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");
* ------------
*/
__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.
*
* Example:
* ------------
* uint64_t start = getnanotime();
* // code section to measure
* trace_performance_since(start, "foobar");
* ------------
*/
__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
* 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
/*
* 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.
*/
#define trace_printf_key(key, ...) \
do { \
if (trace_pass_fl(key)) \
trace_printf_key_fl(TRACE_CONTEXT, __LINE__, key, \
__VA_ARGS__); \
} while (0)
#define trace_printf(...) trace_printf_key(&trace_default_key, __VA_ARGS__)
#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)
#define trace_strbuf(key, data) \
do { \
if (trace_pass_fl(key)) \
trace_strbuf_fl(TRACE_CONTEXT, __LINE__, key, data);\
} while (0)
#define trace_performance(nanos, ...) \
do { \
if (trace_pass_fl(&trace_perf_key)) \
trace_performance_fl(TRACE_CONTEXT, __LINE__, nanos,\
__VA_ARGS__); \
} while (0)
#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)
#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 /* HAVE_VARIADIC_MACROS */
#endif /* TRACE_H */
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