Adding upstream version 1:2.39.2.upstream/1%2.39.2upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 278 insertions, 0 deletions

diff --git a/trace.h b/trace.h
new file mode 100644
index 0000000..4e771f8
--- /dev/null
+++ b/trace.h
@@ -0,0 +1,278 @@
+#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) { .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);
+
+/**
+ * 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);
+
+/*
+ * 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
+
+/**
+ * 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.:
+ *
+ *  #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.
+ */
+
+/**
+ * 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))					    \
+			trace_printf_key_fl(TRACE_CONTEXT, __LINE__, key,   \
+					    __VA_ARGS__);		    \
+	} while (0)
+
+/**
+ * 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))			    \
+			trace_argv_printf_fl(TRACE_CONTEXT, __LINE__,	    \
+					    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))			    \
+			trace_performance_fl(TRACE_CONTEXT, __LINE__, nanos,\
+					     __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))			    \
+			trace_performance_fl(TRACE_CONTEXT, __LINE__,       \
+					     getnanotime() - (start),	    \
+					     __VA_ARGS__);		    \
+	} while (0)
+
+/**
+ * trace_performance_leave(), accepts "const char *format, ...".
+ */
+#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 /* TRACE_H */