98 lines
2.7 KiB
Plaintext
98 lines
2.7 KiB
Plaintext
|
trace API
|
||
|
|
=========
|
||
|
|
|
||
|
|
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
|
||
|
|
------------
|
||
|
|
|
||
|
|
Data Structures
|
||
|
|
---------------
|
||
|
|
|
||
|
|
`struct trace_key`::
|
||
|
|
|
||
|
|
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_print_key(&trace_foo, message);
|
||
|
|
}
|
||
|
|
------------
|
||
|
|
+
|
||
|
|
Note: don't use `const` as the trace implementation stores internal state in
|
||
|
|
the `trace_key` structure.
|
||
|
|
|
||
|
|
Functions
|
||
|
|
---------
|
||
|
|
|
||
|
|
`int trace_want(struct trace_key *key)`::
|
||
|
|
|
||
|
|
Checks whether the trace key is enabled. Used to prevent expensive
|
||
|
|
string formatting before calling one of the printing APIs.
|
||
|
|
|
||
|
|
`void trace_disable(struct trace_key *key)`::
|
||
|
|
|
||
|
|
Disables tracing for the specified key, even if the environment
|
||
|
|
variable was set.
|
||
|
|
|
||
|
|
`void trace_printf(const char *format, ...)`::
|
||
|
|
`void trace_printf_key(struct trace_key *key, const char *format, ...)`::
|
||
|
|
|
||
|
|
Prints a formatted message, similar to printf.
|
||
|
|
|
||
|
|
`void trace_argv_printf(const char **argv, const char *format, ...)``::
|
||
|
|
|
||
|
|
Prints a formatted message, followed by a quoted list of arguments.
|
||
|
|
|
||
|
|
`void trace_strbuf(struct trace_key *key, const struct strbuf *data)`::
|
||
|
|
|
||
|
|
Prints the strbuf, without additional formatting (i.e. doesn't
|
||
|
|
choke on `%` or even `\0`).
|
||
|
|
|
||
|
|
`uint64_t getnanotime(void)`::
|
||
|
|
|
||
|
|
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.
|
||
|
|
|
||
|
|
`void trace_performance(uint64_t nanos, const char *format, ...)`::
|
||
|
|
`void trace_performance_since(uint64_t start, const char *format, ...)`::
|
||
|
|
|
||
|
|
Prints the elapsed time (in nanoseconds), or elapsed time since
|
||
|
|
`start`, followed by a formatted message. Enabled via environment
|
||
|
|
variable `GIT_TRACE_PERFORMANCE`. Used for manual profiling, e.g.:
|
||
|
|
+
|
||
|
|
------------
|
||
|
|
uint64_t start = getnanotime();
|
||
|
|
/* code section to measure */
|
||
|
|
trace_performance_since(start, "foobar");
|
||
|
|
------------
|
||
|
|
+
|
||
|
|
------------
|
||
|
|
uint64_t t = 0;
|
||
|
|
for (;;) {
|
||
|
|
/* ignore */
|
||
|
|
t -= getnanotime();
|
||
|
|
/* code section to measure */
|
||
|
|
t += getnanotime();
|
||
|
|
/* ignore */
|
||
|
|
}
|
||
|
|
trace_performance(t, "frotz");
|
||
|
|
------------
|