perf_counter tools: Add more warnings and fix/annotate them

Enable -Wextra. This found a few real bugs plus a number
of signed/unsigned type mismatches/uncleanlinesses. It
also required a few annotations

All things considered it was still worth it so lets try with
this enabled for now.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/tools/perf/util/strbuf.c b/tools/perf/util/strbuf.c
index 464e7ca..5249d5a 100644
--- a/tools/perf/util/strbuf.c
+++ b/tools/perf/util/strbuf.c
@@ -16,7 +16,7 @@
  */
 char strbuf_slopbuf[1];
 
-void strbuf_init(struct strbuf *sb, size_t hint)
+void strbuf_init(struct strbuf *sb, ssize_t hint)
 {
 	sb->alloc = sb->len = 0;
 	sb->buf = strbuf_slopbuf;
@@ -92,7 +92,8 @@
 
 void strbuf_tolower(struct strbuf *sb)
 {
-	int i;
+	unsigned int i;
+
 	for (i = 0; i < sb->len; i++)
 		sb->buf[i] = tolower(sb->buf[i]);
 }
@@ -264,7 +265,7 @@
 	return res;
 }
 
-ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint)
+ssize_t strbuf_read(struct strbuf *sb, int fd, ssize_t hint)
 {
 	size_t oldlen = sb->len;
 	size_t oldalloc = sb->alloc;
@@ -293,7 +294,7 @@
 
 #define STRBUF_MAXLINK (2*PATH_MAX)
 
-int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint)
+int strbuf_readlink(struct strbuf *sb, const char *path, ssize_t hint)
 {
 	size_t oldalloc = sb->alloc;
 
@@ -301,7 +302,7 @@
 		hint = 32;
 
 	while (hint < STRBUF_MAXLINK) {
-		int len;
+		ssize_t len;
 
 		strbuf_grow(sb, hint);
 		len = readlink(path, sb->buf, hint);
@@ -343,7 +344,7 @@
 	return 0;
 }
 
-int strbuf_read_file(struct strbuf *sb, const char *path, size_t hint)
+int strbuf_read_file(struct strbuf *sb, const char *path, ssize_t hint)
 {
 	int fd, len;