libtraceevent: Add __tep_vprint() for overrides to use

If a program wants to add something special to tep_vprint() but then also
call the default tep_vprint() it can't. If it overrides the function, it
loses the functionality for it.

Add __tep_vprint() for this use case.

Example:

 int tep_vprint(const char *name, enum tep_loglevel level,
	       bool print_err, const char *fmt, va_list ap)
 {
	if (quiet && !strcmp(name, "myprog"))
		return 0;
	return __tep_vprint(name, level, print_err, fmt, ap);
 }

Link: https://lore.kernel.org/linux-trace-devel/20210514205036.1383167-4-rostedt@goodmis.org

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

2 files changed, 29 insertions, 0 deletions

diff --git a/src/event-utils.h b/src/event-utils.h
index 607be0c..d377201 100644
--- a/src/event-utils.h
+++ b/src/event-utils.h
@@ -14,10 +14,16 @@
 
 void tep_warning(const char *fmt, ...);
 void tep_info(const char *fmt, ...);
+
 /* Can be overridden */
 int tep_vprint(const char *name, enum tep_loglevel level,
 	       bool print_err, const char *fmt, va_list ap);
 
+/* The actual call of tep_vprint() for overrides to use */
+int __tep_vprint(const char *name, enum tep_loglevel level,
+		 bool print_err, const char *fmt, va_list ap);
+
+
 #define __deprecated(msg) __attribute__((deprecated("msg")))
 
 /* For backward compatibilty, do not use */
diff --git a/src/parse-utils.c b/src/parse-utils.c
index 04237ba..89bf1cd 100644
--- a/src/parse-utils.c
+++ b/src/parse-utils.c
@@ -9,6 +9,7 @@
 #include <stdarg.h>
 #include <errno.h>
 
+#include "event-utils.h"
 #include "event-parse.h"
 
 #define __weak __attribute__((weak))
@@ -43,6 +44,28 @@ void tep_set_loglevel(enum tep_loglevel level)
 int __weak tep_vprint(const char *name, enum tep_loglevel level,
 		      bool print_err, const char *fmt, va_list ap)
 {
+	return __tep_vprint(name, level, print_err, fmt, ap);
+}
+
+/**
+ * __tep_vprint - print library log messages
+ * @name: name of the library.
+ * @level: severity of the log message. This parameter is not used in this implementation, but as
+ *	   the function is weak and can be overridden, having the log level could be useful
+ *	   for other implementations.
+ * @print_err: whether to print the errno, if non zero.
+ * @fmt: printf format string of the message.
+ * @ap: list of printf parameters.
+ *
+ * This function is used to print all messages from traceevent, tracefs and trace-cmd libraries.
+ * It is defined as weak, so the application that uses those libraries can override it in order
+ * to implement its own logic for printing library logs.
+ *
+ * Return the value of errno at the function enter.
+ */
+int __tep_vprint(const char *name, enum tep_loglevel level,
+		      bool print_err, const char *fmt, va_list ap)
+{
 	int ret = errno;
 
 	if (errno && print_err)