[PATCH v2 0/2] btrfs-progs: Introduce warning and error for common use

[PATCH v2 0/2] btrfs-progs: Introduce warning and error for common use

[Zhao Lei]

Current code use fprintf(stderr, "...") to output warnning and
error information.

The error message have different style, as:
 # grep fprintf *.c
 fprintf(stderr, "Open ctree failed\n");
 fprintf(stderr, "%s: open ctree failed\n", __func__);
 fprintf(stderr, "ERROR: cannot open ctree\n");
 ...

And sometimes, we forgot add tailed '\n', or use printf instead,
as in current code:
 printf("warning, device %llu is missing\n",

This patch introduce warning() and error() as common function,
to make:
1: Each warning and error information have same format
2: Easy to search/change all error message
3: Easy to modify function's internal for debug or other requirement,
   for example:
   print function/linenumber in error()
   dumpstack in error()
   add some trace for some style of message
   add support for -v, -vv, ...
   support for locales
   custom output functions
   support some special device/tty

Converting all source is a big work, this patch convert cmds-scrub.c
We'll convert others these days, and new code can use these function
directly.

Changelog v1->v2:
 1: Rename following functions:
    warningon() -> warning_on()
    erroron() -> error_on()
    Suggested-by: David Sterba <dsterba@suse.cz>
 2: Use static inline instead of macro
    Suggested-by: David Sterba <dsterba@suse.cz>
 3: Add return value of warning/error_on()
    Suggested-by: Qu Wenruo <quwenruo@cn.fujitsu.com>

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>

Zhao Lei (2):
  btrfs-progs: Introduce warning and error for common use
  btrfs-progs: use common warning/error for cmds-scrub.c

 cmds-scrub.c | 171 +++++++++++++++++++++++++++++------------------------------
 utils.h      |  55 +++++++++++++++++++
 2 files changed, 140 insertions(+), 86 deletions(-)

-- 
1.8.5.1

[PATCH v2 1/2] btrfs-progs: Introduce warning and error for common use

[Zhao Lei]

Current code use fprintf(stderr, "...") to output warnning and
error information.

The error message have different style, as:
 # grep fprintf *.c
 fprintf(stderr, "Open ctree failed\n");
 fprintf(stderr, "%s: open ctree failed\n", __func__);
 fprintf(stderr, "ERROR: cannot open ctree\n");
 ...

And sometimes, we forgot add tailed '\n', or use printf instead,
as in current code:
 printf("warning, device %llu is missing\n",

This patch introduce warning() and error() as common function,
to make:
1: Each warning and error information have same format
2: Easy to search/change all error message
3: Easy to modify function's internal for debug or other requirement,
   for example:
   print function/linenumber in error()
   dumpstack in error()
   add some trace for some style of message
   add support for -v, -vv, ...
   support for locales
   custom output functions
   support some special device/tty

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
---
 utils.h | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/utils.h b/utils.h
index dce0a47..c63e372 100644
--- a/utils.h
+++ b/utils.h
@@ -22,6 +22,7 @@
 #include <sys/stat.h>
 #include "ctree.h"
 #include <dirent.h>
+#include <stdarg.h>
 
 #define BTRFS_MKFS_SYSTEM_GROUP_SIZE (4 * 1024 * 1024)
 #define BTRFS_MKFS_SMALL_VOLUME_SIZE (1024 * 1024 * 1024)
@@ -269,4 +270,58 @@ const char *get_argv0_buf(void);
 
 unsigned int get_unit_mode_from_arg(int *argc, char *argv[], int df_mode);
 
+static inline void __veprintf(const char *prefix, const char *format,
+			      va_list ap)
+{
+	if (prefix)
+		fprintf(stderr, "%s", prefix);
+	vfprintf(stderr, format, ap);
+}
+
+static inline void warning(const char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	__veprintf("WARNING: ", fmt, args);
+	va_end(args);
+}
+
+static inline void error(const char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	__veprintf("ERROR: ", fmt, args);
+	va_end(args);
+}
+
+static inline int warning_on(int condition, const char *fmt, ...)
+{
+	if (!condition)
+		return 0;
+
+	va_list args;
+
+	va_start(args, fmt);
+	__veprintf("WARNING: ", fmt, args);
+	va_end(args);
+
+	return 1;
+}
+
+static inline int error_on(int condition, const char *fmt, ...)
+{
+	if (!condition)
+		return 0;
+
+	va_list args;
+
+	va_start(args, fmt);
+	__veprintf("ERROR: ", fmt, args);
+	va_end(args);
+
+	return 1;
+}
+
 #endif
-- 
1.8.5.1

[PATCH v2 2/2] btrfs-progs: use common warning/error for cmds-scrub.c

[Zhao Lei]

Use common warning/error functions in cmds-scrub.c, it can make
message format unified and make code simple.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
---
 cmds-scrub.c | 171 +++++++++++++++++++++++++++++------------------------------
 1 file changed, 85 insertions(+), 86 deletions(-)

diff --git a/cmds-scrub.c b/cmds-scrub.c
index 0340471..ae86279 100644
--- a/cmds-scrub.c
+++ b/cmds-scrub.c
@@ -128,11 +128,6 @@ static void print_scrub_full(struct btrfs_scrub_progress *sp)
 	printf("\tlast_physical: %lld\n", sp->last_physical);
 }
 
-#define ERR(test, ...) do {			\
-	if (test)				\
-		fprintf(stderr, __VA_ARGS__);	\
-} while (0)
-
 #define PRINT_SCRUB_ERROR(test, desc) do {	\
 	if (test)				\
 		printf(" %s=%llu", desc, test);	\
@@ -463,7 +458,7 @@ static int scrub_kvread(int *i, int len, int avail, const char *buf,
 
 #define _SCRUB_INVALID do {						\
 	if (report_errors)						\
-		fprintf(stderr, "WARNING: invalid data in line %d pos "	\
+		warning("invalid data in line %d pos "			\
 			"%d state %d (near \"%.*s\") at %s:%d\n",	\
 			lineno, i, state, 20 > avail ? avail : 20,	\
 			l + i,	__FILE__, __LINE__);			\
@@ -850,8 +845,7 @@ static void *scrub_one_dev(void *ctx)
 		      IOPRIO_PRIO_VALUE(sp->ioprio_class,
 					sp->ioprio_classdata));
 	if (ret)
-		fprintf(stderr,
-			"WARNING: setting ioprio failed: %s (ignored).\n",
+		warning("setting ioprio failed: %s (ignored).\n",
 			strerror(errno));
 
 	ret = ioctl(sp->fd, BTRFS_IOC_SCRUB, &sp->scrub_args);
@@ -1197,9 +1191,9 @@ static int scrub_start(int argc, char **argv, int resume)
 		do_print = 0;
 
 	if (mkdir_p(datafile)) {
-		ERR(!do_quiet, "WARNING: cannot create scrub data "
-			       "file, mkdir %s failed: %s. Status recording "
-			       "disabled\n", datafile, strerror(errno));
+		warning_on(!do_quiet,
+			   "cannot create scrub data file, mkdir %s failed: %s. Status recording disabled\n",
+			   datafile, strerror(errno));
 		do_record = 0;
 	}
 	free(datafile);
@@ -1210,24 +1204,27 @@ static int scrub_start(int argc, char **argv, int resume)
 
 	if (fdmnt < 0) {
 		if (errno == EINVAL)
-			ERR(!do_quiet,
-			    "ERROR: '%s' is not a mounted btrfs device\n",
-			    path);
+			error_on(!do_quiet,
+				 "'%s' is not a mounted btrfs device\n",
+				 path);
 		else
-			ERR(!do_quiet, "ERROR: can't access '%s': %s\n",
-			    path, strerror(errno));
+			error_on(!do_quiet,
+				 "can't access '%s': %s\n",
+				 path, strerror(errno));
 		return 1;
 	}
 
 	ret = get_fs_info(path, &fi_args, &di_args);
 	if (ret) {
-		ERR(!do_quiet, "ERROR: getting dev info for scrub failed: "
-		    "%s\n", strerror(-ret));
+		error_on(!do_quiet,
+			 "getting dev info for scrub failed: %s\n",
+			 strerror(-ret));
 		err = 1;
 		goto out;
 	}
 	if (!fi_args.num_devices) {
-		ERR(!do_quiet, "ERROR: no devices found\n");
+		error_on(!do_quiet,
+			 "no devices found\n");
 		err = 1;
 		goto out;
 	}
@@ -1235,13 +1232,15 @@ static int scrub_start(int argc, char **argv, int resume)
 	uuid_unparse(fi_args.fsid, fsid);
 	fdres = scrub_open_file_r(SCRUB_DATA_FILE, fsid);
 	if (fdres < 0 && fdres != -ENOENT) {
-		ERR(!do_quiet, "WARNING: failed to open status file: "
-		    "%s\n", strerror(-fdres));
+		warning_on(!do_quiet,
+			   "failed to open status file: %s\n",
+			   strerror(-fdres));
 	} else if (fdres >= 0) {
 		past_scrubs = scrub_read_file(fdres, !do_quiet);
 		if (IS_ERR(past_scrubs))
-			ERR(!do_quiet, "WARNING: failed to read status file: "
-			    "%s\n", strerror(-PTR_ERR(past_scrubs)));
+			warning_on(!do_quiet,
+				   "failed to read status file: %s\n",
+				   strerror(-PTR_ERR(past_scrubs)));
 		close(fdres);
 	}
 
@@ -1264,11 +1263,11 @@ static int scrub_start(int argc, char **argv, int resume)
 	 * single devices, there is no reason to prevent this.
 	 */
 	if (!force && is_scrub_running_on_fs(&fi_args, di_args, past_scrubs)) {
-		ERR(!do_quiet,
-		    "ERROR: scrub is already running.\n"
-		    "To cancel use 'btrfs scrub cancel %s'.\n"
-		    "To see the status use 'btrfs scrub status [-d] %s'.\n",
-		    path, path);
+		error_on(!do_quiet,
+			 "scrub is already running.\n"
+			 "To cancel use 'btrfs scrub cancel %s'.\n"
+			 "To see the status use 'btrfs scrub status [-d] %s'.\n",
+			 path, path);
 		err = 1;
 		goto out;
 	}
@@ -1278,7 +1277,8 @@ static int scrub_start(int argc, char **argv, int resume)
 	spc.progress = calloc(fi_args.num_devices * 2, sizeof(*spc.progress));
 
 	if (!t_devs || !sp || !spc.progress) {
-		ERR(!do_quiet, "ERROR: scrub failed: %s", strerror(errno));
+		error_on(!do_quiet,
+			 "scrub failed: %s", strerror(errno));
 		err = 1;
 		goto out;
 	}
@@ -1287,8 +1287,8 @@ static int scrub_start(int argc, char **argv, int resume)
 		devid = di_args[i].devid;
 		ret = pthread_mutex_init(&sp[i].progress_mutex, NULL);
 		if (ret) {
-			ERR(!do_quiet, "ERROR: pthread_mutex_init failed: "
-			    "%s\n", strerror(ret));
+			error_on(!do_quiet, "pthread_mutex_init failed: %s\n",
+				 strerror(ret));
 			err = 1;
 			goto out;
 		}
@@ -1342,7 +1342,7 @@ static int scrub_start(int argc, char **argv, int resume)
 		ret = connect(prg_fd, (struct sockaddr *)&addr, sizeof(addr));
 		if (!ret || errno != ECONNREFUSED) {
 			/* ... yes, so scrub must be running. error out */
-			fprintf(stderr, "ERROR: scrub already running\n");
+			error("scrub already running\n");
 			close(prg_fd);
 			prg_fd = -1;
 			goto out;
@@ -1356,10 +1356,10 @@ static int scrub_start(int argc, char **argv, int resume)
 	if (ret != -1)
 		ret = listen(prg_fd, 100);
 	if (ret == -1) {
-		ERR(!do_quiet, "WARNING: failed to open the progress status "
-		    "socket at %s: %s. Progress cannot be queried\n",
-		    sock_path[0] ? sock_path : SCRUB_PROGRESS_SOCKET_PATH,
-		    strerror(errno));
+		warning_on(!do_quiet,
+			   "failed to open the progress status socket at %s: %s. Progress cannot be queried\n",
+			   sock_path[0] ? sock_path :
+			   SCRUB_PROGRESS_SOCKET_PATH, strerror(errno));
 		if (prg_fd != -1) {
 			close(prg_fd);
 			prg_fd = -1;
@@ -1373,9 +1373,9 @@ static int scrub_start(int argc, char **argv, int resume)
 		ret = scrub_write_progress(&spc_write_mutex, fsid, sp,
 					   fi_args.num_devices);
 		if (ret) {
-			ERR(!do_quiet, "WARNING: failed to write the progress "
-			    "status file: %s. Status recording disabled\n",
-			    strerror(-ret));
+			warning_on(!do_quiet,
+				   "failed to write the progress status file: %s. Status recording disabled\n",
+				   strerror(-ret));
 			do_record = 0;
 		}
 	}
@@ -1383,8 +1383,9 @@ static int scrub_start(int argc, char **argv, int resume)
 	if (do_background) {
 		pid = fork();
 		if (pid == -1) {
-			ERR(!do_quiet, "ERROR: cannot scrub, fork failed: "
-					"%s\n", strerror(errno));
+			error_on(!do_quiet,
+				 "cannot scrub, fork failed: %s\n",
+				 strerror(errno));
 			err = 1;
 			goto out;
 		}
@@ -1402,13 +1403,15 @@ static int scrub_start(int argc, char **argv, int resume)
 			}
 			ret = wait(&stat);
 			if (ret != pid) {
-				ERR(!do_quiet, "ERROR: wait failed: (ret=%d) "
-				    "%s\n", ret, strerror(errno));
+				error_on(!do_quiet,
+					 "wait failed: (ret=%d) %s\n",
+					 ret, strerror(errno));
 				err = 1;
 				goto out;
 			}
 			if (!WIFEXITED(stat) || WEXITSTATUS(stat)) {
-				ERR(!do_quiet, "ERROR: scrub process failed\n");
+				error_on(!do_quiet,
+					 "scrub process failed\n");
 				err = WIFEXITED(stat) ? WEXITSTATUS(stat) : -1;
 				goto out;
 			}
@@ -1434,9 +1437,8 @@ static int scrub_start(int argc, char **argv, int resume)
 					scrub_one_dev, &sp[i]);
 		if (ret) {
 			if (do_print)
-				fprintf(stderr, "ERROR: creating "
-					"scrub_one_dev[%llu] thread failed: "
-					"%s\n", devid, strerror(ret));
+				error("creating scrub_one_dev[%llu] thread failed: %s\n",
+				      devid, strerror(ret));
 			err = 1;
 			goto out;
 		}
@@ -1451,8 +1453,8 @@ static int scrub_start(int argc, char **argv, int resume)
 	ret = pthread_create(&t_prog, NULL, scrub_progress_cycle, &spc);
 	if (ret) {
 		if (do_print)
-			fprintf(stderr, "ERROR: creating progress thread "
-				"failed: %s\n", strerror(ret));
+			error("creating progress thread failed: %s\n",
+			      strerror(ret));
 		err = 1;
 		goto out;
 	}
@@ -1465,25 +1467,23 @@ static int scrub_start(int argc, char **argv, int resume)
 		ret = pthread_join(t_devs[i], NULL);
 		if (ret) {
 			if (do_print)
-				fprintf(stderr, "ERROR: pthread_join failed "
-					"for scrub_one_dev[%llu]: %s\n", devid,
-					strerror(ret));
+				error("pthread_join failed for scrub_one_dev[%llu]: %s\n",
+				      devid, strerror(ret));
 			++err;
 			continue;
 		}
 		if (sp[i].ret && sp[i].ioctl_errno == ENODEV) {
 			if (do_print)
-				fprintf(stderr, "WARNING: device %lld not "
-					"present\n", devid);
+				warning("device %lld not present\n",
+					devid);
 			continue;
 		}
 		if (sp[i].ret && sp[i].ioctl_errno == ECANCELED) {
 			++err;
 		} else if (sp[i].ret) {
 			if (do_print)
-				fprintf(stderr, "ERROR: scrubbing %s failed "
-					"for device id %lld (%s)\n", path,
-					devid, strerror(sp[i].ioctl_errno));
+				error("scrubbing %s failed for device id %lld (%s)\n",
+				      path, devid, strerror(sp[i].ioctl_errno));
 			++err;
 			continue;
 		}
@@ -1524,22 +1524,22 @@ static int scrub_start(int argc, char **argv, int resume)
 
 	/* check for errors from the handling of the progress thread */
 	if (do_print && ret) {
-		fprintf(stderr, "ERROR: progress thread handling failed: %s\n",
-			strerror(ret));
+		error("progress thread handling failed: %s\n",
+		      strerror(ret));
 	}
 
 	/* check for errors returned from the progress thread itself */
 	if (do_print && terr && terr != PTHREAD_CANCELED) {
-		fprintf(stderr, "ERROR: recording progress "
-			"failed: %s\n", strerror(-PTR_ERR(terr)));
+		error("recording progress failed: %s\n",
+		      strerror(-PTR_ERR(terr)));
 	}
 
 	if (do_record) {
 		ret = scrub_write_progress(&spc_write_mutex, fsid, sp,
 					   fi_args.num_devices);
 		if (ret && do_print) {
-			fprintf(stderr, "ERROR: failed to record the result: "
-				"%s\n", strerror(-ret));
+			error("failed to record the result: %s\n",
+			      strerror(-ret));
 		}
 	}
 
@@ -1563,11 +1563,12 @@ out:
 	if (nothing_to_resume)
 		return 2;
 	if (e_uncorrectable) {
-		ERR(!do_quiet, "ERROR: There are uncorrectable errors.\n");
+		error_on(!do_quiet, "There are uncorrectable errors.\n");
 		return 3;
 	}
 	if (e_correctable)
-		ERR(!do_quiet, "WARNING: errors detected during scrubbing, corrected.\n");
+		warning_on(!do_quiet,
+			   "errors detected during scrubbing, corrected.\n");
 
 	return 0;
 }
@@ -1614,12 +1615,11 @@ static int cmd_scrub_cancel(int argc, char **argv)
 	fdmnt = open_path_or_dev_mnt(path, &dirstream);
 	if (fdmnt < 0) {
 		if (errno == EINVAL)
-			fprintf(stderr,
-				"ERROR: '%s' is not a mounted btrfs device\n",
-				path);
+			error("'%s' is not a mounted btrfs device\n",
+			      path);
 		else
-			fprintf(stderr, "ERROR: can't access '%s': %s\n",
-				path, strerror(errno));
+			error("can't access '%s': %s\n",
+			      path, strerror(errno));
 		ret = 1;
 		goto out;
 	}
@@ -1627,8 +1627,9 @@ static int cmd_scrub_cancel(int argc, char **argv)
 	ret = ioctl(fdmnt, BTRFS_IOC_SCRUB_CANCEL, NULL);
 
 	if (ret < 0) {
-		fprintf(stderr, "ERROR: scrub cancel failed on %s: %s\n", path,
-			errno == ENOTCONN ? "not running" : strerror(errno));
+		error("scrub cancel failed on %s: %s\n",
+		      path,
+		      errno == ENOTCONN ? "not running" : strerror(errno));
 		if (errno == ENOTCONN)
 			ret = 2;
 		else
@@ -1719,24 +1720,23 @@ static int cmd_scrub_status(int argc, char **argv)
 
 	if (fdmnt < 0) {
 		if (errno == EINVAL)
-			fprintf(stderr,
-				"ERROR: '%s' is not a mounted btrfs device\n",
-				path);
+			error("'%s' is not a mounted btrfs device\n",
+			      path);
 		else
-			fprintf(stderr, "ERROR: can't access '%s': %s\n",
-				path, strerror(errno));
+			error("can't access '%s': %s\n",
+			      path, strerror(errno));
 		return 1;
 	}
 
 	ret = get_fs_info(path, &fi_args, &di_args);
 	if (ret) {
-		fprintf(stderr, "ERROR: getting dev info for scrub failed: "
-				"%s\n", strerror(-ret));
+		error("getting dev info for scrub failed: %s\n",
+		      strerror(-ret));
 		err = 1;
 		goto out;
 	}
 	if (!fi_args.num_devices) {
-		fprintf(stderr, "ERROR: no devices found\n");
+		error("no devices found\n");
 		err = 1;
 		goto out;
 	}
@@ -1745,9 +1745,8 @@ static int cmd_scrub_status(int argc, char **argv)
 
 	fdres = socket(AF_UNIX, SOCK_STREAM, 0);
 	if (fdres == -1) {
-		fprintf(stderr, "ERROR: failed to create socket to "
-			"receive progress information: %s\n",
-			strerror(errno));
+		error("failed to create socket to receive progress information: %s\n",
+		      strerror(errno));
 		err = 1;
 		goto out;
 	}
@@ -1760,8 +1759,8 @@ static int cmd_scrub_status(int argc, char **argv)
 		close(fdres);
 		fdres = scrub_open_file_r(SCRUB_DATA_FILE, fsid);
 		if (fdres < 0 && fdres != -ENOENT) {
-			fprintf(stderr, "WARNING: failed to open status file: "
-				"%s\n", strerror(-fdres));
+			warning("failed to open status file: %s\n",
+				strerror(-fdres));
 			err = 1;
 			goto out;
 		}
@@ -1770,7 +1769,7 @@ static int cmd_scrub_status(int argc, char **argv)
 	if (fdres >= 0) {
 		past_scrubs = scrub_read_file(fdres, 1);
 		if (IS_ERR(past_scrubs))
-			fprintf(stderr, "WARNING: failed to read status: %s\n",
+			warning("failed to read status: %s\n",
 				strerror(-PTR_ERR(past_scrubs)));
 	}
 	in_progress = is_scrub_running_in_kernel(fdmnt, di_args, fi_args.num_devices);
-- 
1.8.5.1

Re: [PATCH v2 1/2] btrfs-progs: Introduce warning and error for common use

[David Sterba]

On Wed, Sep 16, 2015 at 05:40:46PM +0800, Zhao Lei wrote:
> +static inline void __veprintf(const char *prefix, const char *format,
> +			      va_list ap)
> +{
> +	if (prefix)
> +		fprintf(stderr, "%s", prefix);
> +	vfprintf(stderr, format, ap);

I'm not sure we need this helper. All it does it prints a fixed string,
we can simply add fputs("prefix", stderr) into warning/error functions.

> +static inline int warning_on(int condition, const char *fmt, ...)
> +{
> +	if (!condition)
> +		return 0;
> +
> +	va_list args;

Please do not put declaration(s) after statements.

> +static inline int error_on(int condition, const char *fmt, ...)
> +{
> +	if (!condition)
> +		return 0;
> +
> +	va_list args;

dtto

> +
> +	va_start(args, fmt);
> +	__veprintf("ERROR: ", fmt, args);
> +	va_end(args);
> +
> +	return 1;
> +}

RE: [PATCH v2 1/2] btrfs-progs: Introduce warning and error for common use

[Zhao Lei]

Hi, David Sterba

Thanks for review.

> -----Original Message-----
> From: David Sterba [mailto:dsterba@suse.cz]
> Sent: Friday, September 25, 2015 6:50 PM
> To: Zhao Lei <zhaolei@cn.fujitsu.com>
> Cc: linux-btrfs@vger.kernel.org; Qu Wenruo <quwenruo@cn.fujitsu.com>
> Subject: Re: [PATCH v2 1/2] btrfs-progs: Introduce warning and error for
> common use
> 
> On Wed, Sep 16, 2015 at 05:40:46PM +0800, Zhao Lei wrote:
> > +static inline void __veprintf(const char *prefix, const char *format,
> > +			      va_list ap)
> > +{
> > +	if (prefix)
> > +		fprintf(stderr, "%s", prefix);
> > +	vfprintf(stderr, format, ap);
> 
> I'm not sure we need this helper. All it does it prints a fixed string, we can
> simply add fputs("prefix", stderr) into warning/error functions.
> 
This wrapper is to support locale in future:
Make all message output by one function, then we can put locale code into it
simply.

But now it is hard to introduce locale, because user-land tools
changes output frequently, we need to wait the output about fixed.

So I removed __veprintf() in v3, we can modify it when we need.
 
> > +static inline int warning_on(int condition, const char *fmt, ...) {
> > +	if (!condition)
> > +		return 0;
> > +
> > +	va_list args;
> 
> Please do not put declaration(s) after statements.
> 
Fixed in v3.

> > +static inline int error_on(int condition, const char *fmt, ...) {
> > +	if (!condition)
> > +		return 0;
> > +
> > +	va_list args;
> 
> dtto
> 
Fixed in v3.

Thanks
Zhaolei

> > +
> > +	va_start(args, fmt);
> > +	__veprintf("ERROR: ", fmt, args);
> > +	va_end(args);
> > +
> > +	return 1;
> > +}