[PATCH v2] libtracefs: Implement tracefs_warning()

[PATCH v2] libtracefs: Implement tracefs_warning()

[Tzvetomir Stoyanov (VMware)]

The warning() function is used in a lot of places in the libracefs
library, and it is implemented as a dummy weak function. There is a
weak implementation of the same function in traceevent library, which
could cause a problem when both are used in an application.
Replaced warning() with tracefs_warning() and implemented it as a
weak function, specific to this library.
The tracefs_warning() uses tep_vwarning() from libtraceevent for
printing the warning, which is also a weak function and can be
overridden by the application.
Added a __weak define in the library internal header file.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 Depends on "[PATCH v2] libtraceevent: Add tep_warning()"
 https://lore.kernel.org/linux-trace-devel/20210408042623.3112002-1-tz.stoyanov@gmail.com/

 v2 changes:
  - Use tep_vwarning() for printing the warning message.

 include/tracefs-local.h |  3 ++-
 src/tracefs-events.c    |  2 +-
 src/tracefs-instance.c  |  8 ++++----
 src/tracefs-utils.c     | 17 ++++++++++++-----
 4 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/include/tracefs-local.h b/include/tracefs-local.h
index 73ec113..5a69ef7 100644
--- a/include/tracefs-local.h
+++ b/include/tracefs-local.h
@@ -7,6 +7,7 @@
 #define _TRACE_FS_LOCAL_H
 
 #define __hidden __attribute__((visibility ("hidden")))
+#define __weak __attribute__((weak))
 
 #define ARRAY_SIZE(array) (sizeof(array) / sizeof((array)[0]))
 
@@ -22,7 +23,7 @@ struct tracefs_instance {
 };
 
 /* Can be overridden */
-void warning(const char *fmt, ...);
+void tracefs_warning(const char *fmt, ...);
 
 int str_read_file(const char *file, char **buffer);
 char *trace_append_file(const char *dir, const char *name);
diff --git a/src/tracefs-events.c b/src/tracefs-events.c
index da56943..9a706ab 100644
--- a/src/tracefs-events.c
+++ b/src/tracefs-events.c
@@ -43,7 +43,7 @@ page_to_kbuf(struct tep_handle *tep, void *page, int size)
 
 	kbuffer_load_subbuffer(kbuf, page);
 	if (kbuffer_subbuffer_size(kbuf) > size) {
-		warning("%s: page_size > size", __func__);
+		tracefs_warning("%s: page_size > size", __func__);
 		kbuffer_free(kbuf);
 		kbuf = NULL;
 	}
diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
index bf2fabf..e87b360 100644
--- a/src/tracefs-instance.c
+++ b/src/tracefs-instance.c
@@ -203,7 +203,7 @@ int tracefs_instance_destroy(struct tracefs_instance *instance)
 	int ret = -1;
 
 	if (!instance || !instance->name) {
-		warning("Cannot remove top instance");
+		tracefs_warning("Cannot remove top instance");
 		return -1;
 	}
 
@@ -265,8 +265,8 @@ char *tracefs_instance_get_dir(struct tracefs_instance *instance)
 
 	ret = asprintf(&path, "%s/instances/%s", instance->trace_dir, instance->name);
 	if (ret < 0) {
-		warning("Failed to allocate path for instance %s",
-			 instance->name);
+		tracefs_warning("Failed to allocate path for instance %s",
+				instance->name);
 		return NULL;
 	}
 
@@ -308,7 +308,7 @@ static int write_file(const char *file, const char *str)
 
 	fd = open(file, O_WRONLY | O_TRUNC);
 	if (fd < 0) {
-		warning("Failed to open '%s'", file);
+		tracefs_warning("Failed to open '%s'", file);
 		return -1;
 	}
 	ret = write(fd, str, strlen(str));
diff --git a/src/tracefs-utils.c b/src/tracefs-utils.c
index 0e96f8e..812a41a 100644
--- a/src/tracefs-utils.c
+++ b/src/tracefs-utils.c
@@ -13,7 +13,9 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include <errno.h>
 
+#include <traceevent/event-utils.h>
 #include "tracefs.h"
 #include "tracefs-local.h"
 
@@ -23,8 +25,13 @@
 #define _STR(x) #x
 #define STR(x) _STR(x)
 
-void __attribute__((weak)) warning(const char *fmt, ...)
+void __weak tracefs_warning(const char *fmt, ...)
 {
+	va_list ap;
+
+	va_start(ap, fmt);
+	tep_vwarning("libtracefs", fmt, ap);
+	va_end(ap);
 }
 
 static int mount_tracefs(void)
@@ -76,7 +83,7 @@ __hidden char *trace_find_tracing_dir(void)
 
 	fp = fopen("/proc/mounts", "r");
 	if (!fp) {
-		warning("Can't open /proc/mounts for read");
+		tracefs_warning("Can't open /proc/mounts for read");
 		return NULL;
 	}
 
@@ -103,7 +110,7 @@ __hidden char *trace_find_tracing_dir(void)
 				fspath[PATH_MAX] = 0;
 			} else {
 				if (mount_debugfs() < 0) {
-					warning("debugfs not mounted, please mount");
+					tracefs_warning("debugfs not mounted, please mount");
 					free(debug_str);
 					return NULL;
 				}
@@ -200,7 +207,7 @@ __hidden int str_read_file(const char *file, char **buffer)
 
 	fd = open(file, O_RDONLY);
 	if (fd < 0) {
-		warning("File %s not found", file);
+		tracefs_warning("File %s not found", file);
 		return -1;
 	}
 
@@ -210,7 +217,7 @@ __hidden int str_read_file(const char *file, char **buffer)
 			continue;
 		nbuf = realloc(buf, size+r+1);
 		if (!nbuf) {
-			warning("Failed to allocate file buffer");
+			tracefs_warning("Failed to allocate file buffer");
 			size = -1;
 			break;
 		}
-- 
2.30.2