perfcounter: Handle some IO return values

Building perfcounter tools raises the following warnings:

 builtin-record.c: In function ‘atexit_header’:
 builtin-record.c:464: erreur: ignoring return value of ‘pwrite’, declared with attribute warn_unused_result
 builtin-record.c: In function ‘__cmd_record’:
 builtin-record.c:503: erreur: ignoring return value of ‘read’, declared with attribute warn_unused_result

 builtin-report.c: In function ‘__cmd_report’:
 builtin-report.c:1403: erreur: ignoring return value of ‘read’, declared with attribute warn_unused_result

This patch handles these IO return values.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1245456100-5477-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/builtin-record.c

@@ -461,7 +461,8 @@ static void atexit_header(void)
 {
 	file_header.data_size += bytes_written;
 
-	pwrite(output, &file_header, sizeof(file_header), 0);
+	if (pwrite(output, &file_header, sizeof(file_header), 0) == -1)
+		perror("failed to write on file headers");
 }
 
 static int __cmd_record(int argc, const char **argv)
@@ -500,7 +501,11 @@ static int __cmd_record(int argc, const char **argv)
 	}
 
 	if (!file_new) {
-		read(output, &file_header, sizeof(file_header));
+		if (read(output, &file_header, sizeof(file_header)) == -1) {
+			perror("failed to read file headers");
+			exit(-1);
+		}
+
 		lseek(output, file_header.data_size, SEEK_CUR);
 	}
 

tools/perf/builtin-report.c

@@ -1400,7 +1400,10 @@ static int __cmd_report(void)
 		exit(0);
 	}
 
-	read(input, &file_header, sizeof(file_header));
+	if (read(input, &file_header, sizeof(file_header)) == -1) {
+		perror("failed to read file headers");
+		exit(-1);
+	}
 
 	if (sort__has_parent &&
 	    !(file_header.sample_type & PERF_SAMPLE_CALLCHAIN)) {