Subject: [PATCH v6 08/11] trace: add 'file:line' to all trace output

From: Karsten Blees <[email-masked]>
Date: Fri, 20 Jun 2014 23:08:29 +0200

This is useful to see where trace output came from.

Add 'const char *file, int line' parameters to the printing functions and
rename them to *_fl.

Add trace_printf* and trace_strbuf macros resolving to the *_fl functions
and let the preprocessor fill in __FILE__ and __LINE__.

As the trace_printf* functions take a variable number of arguments, this
requires variadic macros (i.e. '#define foo(...) foo_impl(__VA_ARGS__)'.
Though part of C99, it is unclear whether older compilers support this.
Thus keep the old functions and only enable variadic macros for GNUC and
MSVC 2005+ (_MSC_VER 1400). This has the nice side effect that the old
C-style declarations serve as documentation how the macros are to be used.

Print 'file:line ' as prefix to each trace line. Align the remaining trace
output at column 40 to accommodate 18 char file names + 4 digit line
number (currently there are 30 *.c files of length 18 and just 11 of 19).
Trace output from longer source files (e.g. builtin/receive-pack.c) will
not be aligned.

Signed-off-by: Karsten Blees <[email-masked]>
---
 git-compat-util.h |  4 ++++
 trace.c           | 72 +++++++++++++++++++++++++++++++++++++++++++++----------
 trace.h           | 49 +++++++++++++++++++++++++++++++++++++
 3 files changed, 113 insertions(+), 12 deletions(-)

diff --git a/git-compat-util.h b/git-compat-util.h
index b6f03b3..4dd065d 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -704,6 +704,10 @@ void git_qsort(void *base, size_t nmemb, size_t size,
 #endif
 #endif
 
+#if defined(__GNUC__) || (_MSC_VER >= 1400)
+#define HAVE_VARIADIC_MACROS 1
+#endif
+
 /*
  * Preserves errno, prints a message, but gives no warning for ENOENT.
  * Always returns the return value of unlink(2).
diff --git a/trace.c b/trace.c
index 869fb7b..5844f31 100644
--- a/trace.c
+++ b/trace.c
@@ -79,7 +79,8 @@ static void do_trace_print(const char *key, const struct strbuf *buf)
 
 static int trace_bare = -1;
 
-static int prepare_trace_line(const char *key, struct strbuf *buf)
+static int prepare_trace_line(const char *file, int line, const char *key,
+			      struct strbuf *buf)
 {
 	struct timeval tv;
 	struct tm tm;
@@ -103,6 +104,14 @@ static int prepare_trace_line(const char *key, struct strbuf *buf)
 	strbuf_addf(buf, "%02d:%02d:%02d.%06ld ", tm.tm_hour, tm.tm_min,
 		    tm.tm_sec, tv.tv_usec);
 
+#ifdef HAVE_VARIADIC_MACROS
+	/* print file:line */
+	strbuf_addf(buf, "%s:%d ", file, line);
+	/* align trace output (column 40 catches most files names in git) */
+	while (buf->len < 40)
+		strbuf_addch(buf, ' ');
+#endif
+
 	return 1;
 }
 
@@ -116,49 +125,52 @@ static void print_trace_line(const char *key, struct strbuf *buf)
 	strbuf_release(buf);
 }
 
-static void trace_vprintf(const char *key, const char *format, va_list ap)
+static void trace_vprintf_fl(const char *file, int line, const char *key,
+			     const char *format, va_list ap)
 {
 	struct strbuf buf = STRBUF_INIT;
 
-	if (!prepare_trace_line(key, &buf))
+	if (!prepare_trace_line(file, line, key, &buf))
 		return;
 
 	strbuf_vaddf(&buf, format, ap);
 	print_trace_line(key, &buf);
 }
 
-void trace_argv_printf(const char **argv, const char *format, ...)
+static void trace_argv_vprintf_fl(const char *file, int line,
+				  const char **argv, const char *format,
+				  va_list ap)
 {
 	struct strbuf buf = STRBUF_INIT;
-	va_list ap;
 
-	if (!prepare_trace_line("GIT_TRACE", &buf))
+	if (!prepare_trace_line(file, line, "GIT_TRACE", &buf))
 		return;
 
-	va_start(ap, format);
 	strbuf_vaddf(&buf, format, ap);
-	va_end(ap);
 
 	sq_quote_argv(&buf, argv, 0);
 	print_trace_line("GIT_TRACE", &buf);
 }
 
-void trace_strbuf(const char *key, const struct strbuf *data)
+void trace_strbuf_fl(const char *file, int line, const char *key,
+		     const struct strbuf *data)
 {
 	struct strbuf buf = STRBUF_INIT;
 
-	if (!prepare_trace_line(key, &buf))
+	if (!prepare_trace_line(file, line, key, &buf))
 		return;
 
 	strbuf_addbuf(&buf, data);
 	print_trace_line(key, &buf);
 }
 
+#ifndef HAVE_VARIADIC_MACROS
+
 void trace_printf(const char *format, ...)
 {
 	va_list ap;
 	va_start(ap, format);
-	trace_vprintf("GIT_TRACE", format, ap);
+	trace_vprintf_fl(NULL, 0, "GIT_TRACE", format, ap);
 	va_end(ap);
 }
 
@@ -166,10 +178,46 @@ void trace_printf_key(const char *key, const char *format, ...)
 {
 	va_list ap;
 	va_start(ap, format);
-	trace_vprintf(key, format, ap);
+	trace_vprintf_fl(NULL, 0, key, format, ap);
 	va_end(ap);
 }
 
+void trace_argv_printf(const char **argv, const char *format, ...)
+{
+	va_list ap;
+	va_start(ap, format);
+	trace_argv_vprintf_fl(NULL, 0, argv, format, ap);
+	va_end(ap);
+}
+
+void trace_strbuf(const char *key, const struct strbuf *data)
+{
+	trace_strbuf_fl(NULL, 0, key, data);
+}
+
+#else
+
+void trace_printf_key_fl(const char *file, int line, const char *key,
+			 const char *format, ...)
+{
+	va_list ap;
+	va_start(ap, format);
+	trace_vprintf_fl(file, line, key, format, ap);
+	va_end(ap);
+}
+
+void trace_argv_printf_fl(const char *file, int line, const char **argv,
+			  const char *format, ...)
+{
+	va_list ap;
+	va_start(ap, format);
+	trace_argv_vprintf_fl(file, line, argv, format, ap);
+	va_end(ap);
+}
+
+#endif /* HAVE_VARIADIC_MACROS */
+
+
 static const char *quote_crnl(const char *path)
 {
 	static char new_path[PATH_MAX];
diff --git a/trace.h b/trace.h
index 5c7f2dc..916dc2b 100644
--- a/trace.h
+++ b/trace.h
@@ -7,6 +7,8 @@
 extern void trace_repo_setup(const char *prefix);
 extern int trace_want(const char *key);
 
+#ifndef HAVE_VARIADIC_MACROS
+
 __attribute__((format (printf, 1, 2)))
 extern void trace_printf(const char *format, ...);
 
@@ -18,4 +20,51 @@ extern void trace_argv_printf(const char **argv, const char *format, ...);
 
 extern void trace_strbuf(const char *key, const struct strbuf *data);
 
+#else
+
+/*
+ * Macros to add file:line - see above for C-style declarations of how these
+ * should be used.
+ */
+
+/*
+ * 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(...) \
+	trace_printf_key_fl(__FILE__, __LINE__, "GIT_TRACE", __VA_ARGS__)
+
+#define trace_printf_key(key, ...) \
+	trace_printf_key_fl(__FILE__, __LINE__, key, __VA_ARGS__)
+
+#define trace_argv_printf(argv, ...) \
+	trace_argv_printf_fl(__FILE__, __LINE__, argv, __VA_ARGS__)
+
+#define trace_strbuf(key, data) \
+	trace_strbuf_fl(__FILE__, __LINE__, key, data)
+
+/* backend functions, use non-*fl macros instead */
+__attribute__((format (printf, 4, 5)))
+extern void trace_printf_key_fl(const char *file, int line, const char *key,
+				const char *format, ...);
+__attribute__((format (printf, 4, 5)))
+extern void trace_argv_printf_fl(const char *file, int line, const char **argv,
+				 const char *format, ...);
+extern void trace_strbuf_fl(const char *file, int line, const char *key,
+			    const struct strbuf *data);
+
+#endif /* HAVE_VARIADIC_MACROS */
+
 #endif /* TRACE_H */
-- 
2.0.0.402.g13b8b25

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