parse-events: Show where error occurred in filtering

Show a nice pointer where an error occurred in filtering:

 # trace-cmd report -F 'sched_switch:(next_pid==x)||)prev_pid == 1'
version = 6
cpus=4
trace-cmd: No such file or directory
  Error filtering: sched_switch:(next_pid==x)||)prev_pid == 1
(next_pid==x)||)prev_pid == 1
               ^
Expected end where ) was found

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

4 files changed, 39 insertions, 3 deletions

diff --git a/parse-events.c b/parse-events.c
index beab8f3..99c9593 100644
--- a/parse-events.c
+++ b/parse-events.c
@@ -53,6 +53,16 @@ static void init_input_buf(const char *buf, unsigned long long size)
         input_buf_ptr = 0;
 }
 
+const char *pevent_get_input_buf(void)
+{
+        return input_buf;
+}
+
+unsigned long long pevent_get_input_buf_ptr(void)
+{
+        return input_buf_ptr;
+}
+
 struct event_handler {
         struct event_handler            *next;
         int                             id;
diff --git a/parse-events.h b/parse-events.h
index 4732acf..3ffe56f 100644
--- a/parse-events.h
+++ b/parse-events.h
@@ -558,6 +558,8 @@ void pevent_buffer_init(const char *buf, unsigned long long size);
 enum event_type pevent_read_token(char **tok);
 void pevent_free_token(char *token);
 int pevent_peek_char(void);
+const char *pevent_get_input_buf(void);
+unsigned long long pevent_get_input_buf_ptr(void);
 
 /* for debugging */
 void pevent_print_funcs(struct pevent *pevent);
diff --git a/parse-filter.c b/parse-filter.c
index 0eeab5e..e5ff909 100644
--- a/parse-filter.c
+++ b/parse-filter.c
@@ -43,16 +43,37 @@ struct event_list {
 
 static void show_error(char **error_str, const char *fmt, ...)
 {
+        unsigned long long index;
+        const char *input;
+        char *error;
         va_list ap;
+        int len;
+        int i;
 
         if (!error_str)
                 return;
 
-        *error_str = malloc_or_die(MAX_ERR_STR_SIZE);
+        input = pevent_get_input_buf();
+        index = pevent_get_input_buf_ptr();
+        len = input ? strlen(input) : 0;
+
+        error = malloc_or_die(MAX_ERR_STR_SIZE + (len*2) + 3);
+
+        if (len) {
+                strcpy(error, input);
+                error[len] = '\n';
+                for (i = 1; i < len && i < index; i++)
+                        error[len+i] = ' ';
+                error[len + i] = '^';
+                error[len + i + 1] = '\n';
+                len += i+2;
+        }
 
         va_start(ap, fmt);
-        vsnprintf(*error_str, MAX_ERR_STR_SIZE, fmt, ap);
+        vsnprintf(error + len, MAX_ERR_STR_SIZE, fmt, ap);
         va_end(ap);
+
+        *error_str = error;
 }
 
 static void free_token(char *token)
@@ -1055,6 +1076,9 @@ int pevent_filter_add_filter_str(struct event_filter *filter,
         int len;
         int ret;
 
+        /* clear buffer to reset show error */
+        pevent_buffer_init("", 0);
+
         if (error_str)
                 *error_str = NULL;
 
diff --git a/trace-read.c b/trace-read.c
index dc79cf1..a4c3538 100644
--- a/trace-read.c
+++ b/trace-read.c
@@ -269,7 +269,7 @@ static void process_filters(struct tracecmd_input *handle)
                                                    filter->filter,
                                                    &errstr);
                 if (ret < 0)
-                        die("Error filtering: %s\n   %s",
+                        die("Error filtering: %s\n%s",
                             filter->filter, errstr);
                 free(errstr);
                 free(filter);