[PATCH v2] libtraceeval: Fix comparing unsigned against zero

[PATCH v2] libtraceeval: Fix comparing unsigned against zero

[Steven Rostedt]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

nr_key_types and nr_val_types are both size_t which is an unsized number.
A compare against zero is always false:

	if (teval->nr_key_types < 0)

Change them to ssize_t (signed type).

Also change the few places the "size_t i" is used where it does:

	for (; i >= 0; i--)

as that too needs to be signed to work.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
Changes since v1: https://lore.kernel.org/linux-trace-devel/20230927041629.43ffbfd9@rorschach.local.home

  - Use ssize_t type instead of typecasting (Ross Zwisler)

 src/eval-local.h | 4 ++--
 src/histograms.c | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/eval-local.h b/src/eval-local.h
index 5c3918f17cc1..f7a9de4628ba 100644
--- a/src/eval-local.h
+++ b/src/eval-local.h
@@ -66,8 +66,8 @@ struct traceeval {
 	struct traceeval_type		*key_types;
 	struct traceeval_type		*val_types;
 	struct hash_table		*hist;
-	size_t				nr_key_types;
-	size_t				nr_val_types;
+	ssize_t				nr_key_types;
+	ssize_t				nr_val_types;
 };
 
 struct traceeval_iterator {
diff --git a/src/histograms.c b/src/histograms.c
index 96f0926f062c..9f9594aa9546 100644
--- a/src/histograms.c
+++ b/src/histograms.c
@@ -159,7 +159,7 @@ static size_t type_alloc(const struct traceeval_type *defs,
 {
 	struct traceeval_type *new_defs = NULL;
 	size_t size;
-	size_t i;
+	ssize_t i;
 
 	*copy = NULL;
 
@@ -196,7 +196,7 @@ fail:
 	else
 		print_err("traceeval_type list missing a name");
 
-	for (; i >=0; i--)
+	for (; i >= 0; i--)
 		free(new_defs[i].name);
 	free(new_defs);
 	return -1;
@@ -785,7 +785,7 @@ static int update_entry(struct traceeval *teval, struct entry *entry,
 	union traceeval_data *copy = entry->vals;
 	union traceeval_data old[teval->nr_val_types];
 	size_t size = teval->nr_val_types;
-	size_t i;
+	ssize_t i;
 
 	if (!size)
 		return 0;
-- 
2.40.1

Re: [PATCH v2] libtraceeval: Fix comparing unsigned against zero

[Ross Zwisler]

On Tue, Oct 03, 2023 at 09:10:32AM -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
> 
> nr_key_types and nr_val_types are both size_t which is an unsized number.
> A compare against zero is always false:
> 
> 	if (teval->nr_key_types < 0)
> 
> Change them to ssize_t (signed type).
> 
> Also change the few places the "size_t i" is used where it does:
> 
> 	for (; i >= 0; i--)
> 
> as that too needs to be signed to work.
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Reviewed-by: Ross Zwisler <zwisler@google.com>