[PATCH] Trace into open fd and refactor tracing code.

[PATCH] Trace into open fd and refactor tracing code.

[Christian Couder]

Now if GIT_TRACE is set to an integer value greater than 1
and lower than 10, we interpret this as an open fd value
and we trace into it. Note that this behavior is not
compatible with the previous one.

We also trace whole messages using one write(2) call to
make sure messages from processes do net get mixed up in
the middle.

It's now possible to run the tests like this:

	GIT_TRACE=9 make test 9>/var/tmp/trace.log

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>

---
 Makefile       |    2 -
 cache.h        |    6 +++
 exec_cmd.c     |   18 +-------
 git.c          |   25 ++---------
 imap-send.c    |   25 -----------
 quote.c        |   32 ++++++++++++++
 quote.h        |    1 
 t/test-lib.sh  |    1 
 trace.c        |  125 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 write_or_die.c |   25 +++++++++++
 10 files changed, 196 insertions(+), 64 deletions(-)

diff --git a/Makefile b/Makefile
index 48eb5f5..8c9de6b 100644
--- a/Makefile
+++ b/Makefile
@@ -260,7 +260,7 @@ LIB_OBJS = \
 	server-info.o setup.o sha1_file.o sha1_name.o strbuf.o \
 	tag.o tree.o usage.o config.o environment.o ctype.o copy.o \
 	fetch-clone.o revision.o pager.o tree-walk.o xdiff-interface.o \
-	write_or_die.o \
+	write_or_die.o trace.o \
 	alloc.o merge-file.o path-list.o unpack-trees.o help.o $(DIFF_OBJS)
 
 BUILTIN_OBJS = \
diff --git a/cache.h b/cache.h
index e26ab7d..9a700ee 100644
--- a/cache.h
+++ b/cache.h
@@ -401,6 +401,7 @@ extern char git_commit_encoding[MAX_ENCO
 
 extern int copy_fd(int ifd, int ofd);
 extern void write_or_die(int fd, const void *buf, size_t count);
+extern int write_or_whine(int fd, const void *buf, size_t count, const char *msg);
 
 /* Finish off pack transfer receiving end */
 extern int receive_unpack_pack(int fd[2], const char *me, int quiet, int);
@@ -426,4 +427,9 @@ extern struct commit *alloc_commit_node(
 extern struct tag *alloc_tag_node(void);
 extern void alloc_report(void);
 
+/* trace.c */
+extern int nfvasprintf(char **str, const char *fmt, va_list va);
+extern void trace_printf(const char *format, ...);
+extern void trace_argv_printf(const char **argv, int count, const char *format, ...);
+
 #endif /* CACHE_H */
diff --git a/exec_cmd.c b/exec_cmd.c
index e30936d..5d6a124 100644
--- a/exec_cmd.c
+++ b/exec_cmd.c
@@ -97,26 +97,12 @@ int execv_git_cmd(const char **argv)
 		tmp = argv[0];
 		argv[0] = git_command;
 
-		if (getenv("GIT_TRACE")) {
-			const char **p = argv;
-			fputs("trace: exec:", stderr);
-			while (*p) {
-				fputc(' ', stderr);
-				sq_quote_print(stderr, *p);
-				++p;
-			}
-			putc('\n', stderr);
-			fflush(stderr);
-		}
+		trace_argv_printf(argv, -1, "trace: exec:");
 
 		/* execve() can only ever return if it fails */
 		execve(git_command, (char **)argv, environ);
 
-		if (getenv("GIT_TRACE")) {
-			fprintf(stderr, "trace: exec failed: %s\n",
-				strerror(errno));
-			fflush(stderr);
-		}
+		trace_printf("trace: exec failed: %s\n", strerror(errno));
 
 		argv[0] = tmp;
 	}
diff --git a/git.c b/git.c
index a01d195..0b78697 100644
--- a/git.c
+++ b/git.c
@@ -179,17 +179,9 @@ static int handle_alias(int *argcp, cons
 		if (!strcmp(alias_command, new_argv[0]))
 			die("recursive alias: %s", alias_command);
 
-		if (getenv("GIT_TRACE")) {
-			int i;
-			fprintf(stderr, "trace: alias expansion: %s =>",
-				alias_command);
-			for (i = 0; i < count; ++i) {
-				fputc(' ', stderr);
-				sq_quote_print(stderr, new_argv[i]);
-			}
-			fputc('\n', stderr);
-			fflush(stderr);
-		}
+		trace_argv_printf(new_argv, count,
+				  "trace: alias expansion: %s =>",
+				  alias_command);
 
 		new_argv = realloc(new_argv, sizeof(char*) *
 				   (count + *argcp + 1));
@@ -291,16 +283,7 @@ static void handle_internal_command(int 
 			prefix = setup_git_directory();
 		if (p->option & USE_PAGER)
 			setup_pager();
-		if (getenv("GIT_TRACE")) {
-			int j;
-			fprintf(stderr, "trace: built-in: git");
-			for (j = 0; j < argc; ++j) {
-				fputc(' ', stderr);
-				sq_quote_print(stderr, argv[j]);
-			}
-			putc('\n', stderr);
-			fflush(stderr);
-		}
+		trace_argv_printf(argv, argc, "trace: built-in: git");
 
 		exit(p->fn(argc, argv, prefix));
 	}
diff --git a/imap-send.c b/imap-send.c
index 65c71c6..6a52dbd 100644
--- a/imap-send.c
+++ b/imap-send.c
@@ -110,7 +110,6 @@ static char *next_arg( char ** );
 
 static void free_generic_messages( message_t * );
 
-static int nfvasprintf( char **str, const char *fmt, va_list va );
 static int nfsnprintf( char *buf, int blen, const char *fmt, ... );
 
 
@@ -372,21 +371,6 @@ free_generic_messages( message_t *msgs )
 }
 
 static int
-git_vasprintf( char **strp, const char *fmt, va_list ap )
-{
-	int len;
-	char tmp[1024];
-
-	if ((len = vsnprintf( tmp, sizeof(tmp), fmt, ap )) < 0 || !(*strp = xmalloc( len + 1 )))
-		return -1;
-	if (len >= (int)sizeof(tmp))
-		vsprintf( *strp, fmt, ap );
-	else
-		memcpy( *strp, tmp, len + 1 );
-	return len;
-}
-
-static int
 nfsnprintf( char *buf, int blen, const char *fmt, ... )
 {
 	int ret;
@@ -399,15 +383,6 @@ nfsnprintf( char *buf, int blen, const c
 	return ret;
 }
 
-static int
-nfvasprintf( char **str, const char *fmt, va_list va )
-{
-	int ret = git_vasprintf( str, fmt, va );
-	if (ret < 0)
-		die( "Fatal: Out of memory\n");
-	return ret;
-}
-
 static struct {
 	unsigned char i, j, s[256];
 } rs;
diff --git a/quote.c b/quote.c
index e220dcc..f90091e 100644
--- a/quote.c
+++ b/quote.c
@@ -74,6 +74,38 @@ char *sq_quote(const char *src)
 	return buf;
 }
 
+char *sq_quote_argv(const char** argv, int count)
+{
+	char *buf, *to;
+	int i;
+	size_t len = 0;
+
+	/* Count argv if needed. */
+	if (count < 0) {
+		for (count = 0; argv[count]; count++)
+			; /* just counting */
+	}
+
+	/* Special case: no argv. */
+	if (!count)
+		return xcalloc(1,1);
+	
+	/* Get destination buffer length. */
+	for (i = 0; i < count; i++)
+		len += sq_quote_buf(NULL, 0, argv[i]) + 1;
+
+	/* Alloc destination buffer. */
+	to = buf = xmalloc(len + 1);
+
+	/* Copy into destination buffer. */
+	for (i = 0; i < count; ++i) {
+		*to++ = ' ';
+		to += sq_quote_buf(to, len, argv[i]);
+	}
+
+	return buf;
+}
+
 char *sq_dequote(char *arg)
 {
 	char *dst = arg;
diff --git a/quote.h b/quote.h
index fc5481e..a6c4611 100644
--- a/quote.h
+++ b/quote.h
@@ -31,6 +31,7 @@ #include <stdio.h>
 extern char *sq_quote(const char *src);
 extern void sq_quote_print(FILE *stream, const char *src);
 extern size_t sq_quote_buf(char *dst, size_t n, const char *src);
+extern char *sq_quote_argv(const char** argv, int count);
 
 /* This unwraps what sq_quote() produces in place, but returns
  * NULL if the input does not look like what sq_quote would have
diff --git a/t/test-lib.sh b/t/test-lib.sh
index b6d119a..695243e 100755
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -28,7 +28,6 @@ unset GIT_DIR
 unset GIT_EXTERNAL_DIFF
 unset GIT_INDEX_FILE
 unset GIT_OBJECT_DIRECTORY
-unset GIT_TRACE
 unset SHA1_FILE_DIRECTORIES
 unset SHA1_FILE_DIRECTORY
 export GIT_AUTHOR_EMAIL GIT_AUTHOR_NAME
diff --git a/trace.c b/trace.c
new file mode 100644
index 0000000..939fa76
--- /dev/null
+++ b/trace.c
@@ -0,0 +1,125 @@
+/*
+ * GIT - The information manager from hell
+ *
+ * Copyright (C) 2000-2002 Michael R. Elkins <me@mutt.org>
+ * Copyright (C) 2002-2004 Oswald Buddenhagen <ossi@users.sf.net>
+ * Copyright (C) 2004 Theodore Y. Ts'o <tytso@mit.edu>
+ * Copyright (C) 2006 Mike McCormack
+ * Copyright (C) 2006 Christian Couder 
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include "cache.h"
+#include "quote.h"
+
+/* Stolen from "imap-send.c". */
+static int git_vasprintf(char **strp, const char *fmt, va_list ap)
+{
+	int len;
+	char tmp[1024];
+
+	if ((len = vsnprintf(tmp, sizeof(tmp), fmt, ap)) < 0 ||
+	    !(*strp = xmalloc(len + 1)))
+		return -1;
+	if (len >= (int)sizeof(tmp))
+		vsprintf(*strp, fmt, ap);
+	else
+		memcpy(*strp, tmp, len + 1);
+	return len;
+}
+
+/* Stolen from "imap-send.c". */
+int nfvasprintf(char **str, const char *fmt, va_list va)
+{
+	int ret = git_vasprintf(str, fmt, va);
+	if (ret < 0)
+		die("Fatal: Out of memory\n");
+	return ret;
+}
+
+/* Get a trace file descriptor from GIT_TRACE env variable. */
+static int get_trace_fd()
+{
+	char *trace = getenv("GIT_TRACE");
+
+	if (!trace || !strcmp(trace, "0") || !strcasecmp(trace," false"))
+		return 0;
+	if (!strcmp(trace, "1") || !strcasecmp(trace, "true"))
+		return STDERR_FILENO;
+	if (strlen(trace) == 1 && isdigit(*trace))
+		return atoi(trace);
+
+	fprintf(stderr, "What does '%s' for GIT_TRACE means ?\n", trace);
+	fprintf(stderr, "Defaulting to tracing on stderr...\n");
+	return STDERR_FILENO;
+}
+
+static const char err_msg[] = "Could not trace into fd given by "
+	"GIT_TRACE environment variable";
+
+void trace_printf(const char *format, ...)
+{
+	char *trace_str;
+	va_list rest;
+	int fd = get_trace_fd();
+
+	if (!fd)
+		return;
+
+	va_start(rest, format);
+	nfvasprintf(&trace_str, format, rest);
+	va_end(rest);
+
+	write_or_whine(fd, trace_str, strlen(trace_str), err_msg);
+
+	free(trace_str);
+}
+
+void trace_argv_printf(const char **argv, int count, const char *format, ...)
+{
+	char *argv_str, *format_str, *trace_str;
+	size_t argv_len, format_len, trace_len;
+	va_list rest;
+	int fd = get_trace_fd();
+
+	if (!fd)
+		return;
+
+	/* Get the argv string. */
+	argv_str = sq_quote_argv(argv, count);
+	argv_len = strlen(argv_str);
+
+	/* Get the formated string. */
+	va_start(rest, format);
+	nfvasprintf(&format_str, format, rest);
+	va_end(rest);
+
+	/* Allocate buffer for trace string. */
+	format_len = strlen(format_str);
+	trace_len = argv_len + format_len + 1; /* + 1 for \n */
+	trace_str = xmalloc(trace_len + 1);
+
+	/* Copy everything into the trace string. */
+	strncpy(trace_str, format_str, format_len);
+	strncpy(trace_str + format_len, argv_str, argv_len);
+	strcpy(trace_str + trace_len - 1, "\n");
+
+	write_or_whine(fd, trace_str, trace_len, err_msg);
+	
+	free(argv_str);
+	free(format_str);
+	free(trace_str);
+}
diff --git a/write_or_die.c b/write_or_die.c
index ab4cb8a..bfe4eeb 100644
--- a/write_or_die.c
+++ b/write_or_die.c
@@ -18,3 +18,28 @@ void write_or_die(int fd, const void *bu
 		p += written;
 	}
 }
+
+int write_or_whine(int fd, const void *buf, size_t count, const char *msg)
+{
+	const char *p = buf;
+	ssize_t written;
+
+	while (count > 0) {
+		written = xwrite(fd, p, count);
+		if (written == 0) {
+			fprintf(stderr, "%s: disk full?\n", msg);
+			return 0;
+		}
+		else if (written < 0) {
+			if (errno == EPIPE)
+				exit(0);
+			fprintf(stderr, "%s: write error (%s)\n",
+				msg, strerror(errno));
+			return 0;
+		}
+		count -= written;
+		p += written;
+	}
+
+	return 1;
+}
-- 
1.4.2.g584f7-dirty

Re: [PATCH] Trace into open fd and refactor tracing code.

[Linus Torvalds]

On Thu, 31 Aug 2006, Christian Couder wrote:
>
> It's now possible to run the tests like this:
> 
> 	GIT_TRACE=9 make test 9>/var/tmp/trace.log

Wouldn't it me _much_ more natural to instead do

	GIT_TRACE=/var/tmp/trace.log make test

and just have git open that file with "O_APPEND | O_CREAT"?

Maybe make the rule be that this only happens if the GIT_TRACE variable 
starts with a '/' character (ie you have to make it an absolute path).

That way, if you want to do the fd thing, you can always just do

	GIT_TRACE=/proc/self/fd/9 make test 9>/var/tmp/trace.log

although I really don't know how well that works across a fork/exec that 
may or may not be closing the file descriptor (I think it's much simpler 
and more obvious to just give the filename directly).

Hmm?

			Linus

Re: [PATCH] Trace into open fd and refactor tracing code.

[Junio C Hamano]

Linus Torvalds <torvalds@osdl.org> writes:

> That way, if you want to do the fd thing, you can always just do
>
> 	GIT_TRACE=/proc/self/fd/9 make test 9>/var/tmp/trace.log
>
> although I really don't know how well that works across a fork/exec that 
> may or may not be closing the file descriptor (I think it's much simpler 
> and more obvious to just give the filename directly).

Actually it was me who suggested the use of fd directly, along
with trying to do one message in a single write (i.e. not doing
stdio as much as possible).

Process A has fd=9 opened to /var/tmp/trace.log and forks
process B.

(1) process B execs something else, and just writes into fd=9

or

(2) process B execs something else, perhaps after closing fd=9,
    and the exec'ed image opens /var/tmp/trace.log with
    "O_APPEND|O_CREAT" and gets a fd; it writes into this fd.

I somehow felt there would be less interference between writes
issued by process A and process B, but probably I am mistaken.

Re: [PATCH] Trace into open fd and refactor tracing code.

[Linus Torvalds]

On Thu, 31 Aug 2006, Junio C Hamano wrote:
> 
> Actually it was me who suggested the use of fd directly, along
> with trying to do one message in a single write (i.e. not doing
> stdio as much as possible).

I definitely agree with the "one message in a single write" thing.

That's in fact required to make sure that O_APPEND works properly (ie that 
you don't have potentially different processes mixing output)

> I somehow felt there would be less interference between writes
> issued by process A and process B, but probably I am mistaken.

The atomicity guarantees are the same regardless of whether you do a 
separate open(), the only thing that matters is that you do want to try to 
do messages with a single "write()" call, and that you use O_APPEND. That 
should guarantee that you get good behaviour.

Without O_APPEND, you would obviously have to share one single file 
descriptor, because otherwise people will just be writing all over each 
other.

			Linus