The option -Wptr-subtraction-blows warns when pointer subtraction
is done and the base size is not a power-of-2.
However, the current message doesn't give much context.
Change this by giving the base type and the size in the warning.
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
evaluate.c | 2 +-
validation/ptr-sub-blows.c | 22 ++++++++++++++++++++++
2 files changed, 23 insertions(+), 1 deletion(-)
create mode 100644 validation/ptr-sub-blows.c
diff --git a/evaluate.c b/evaluate.c
index 4be4e8e5b..7818af48f 100644
--- a/evaluate.c
+++ b/evaluate.c
@@ -848,7 +848,7 @@ static struct symbol *evaluate_ptr_sub(struct expression *expr)
if (value & (value-1)) {
if (Wptr_subtraction_blows)
- warning(expr->pos, "potentially expensive pointer subtraction");
+ warning(expr->pos, "potentially expensive pointer subtraction (size = %lu for %s)", value, show_typename(lbase));
}
sub->op = '-';
diff --git a/validation/ptr-sub-blows.c b/validation/ptr-sub-blows.c
new file mode 100644
index 000000000..433bd4e0c
--- /dev/null
+++ b/validation/ptr-sub-blows.c
@@ -0,0 +1,22 @@
+static int ok(int *a, int *b)
+{
+ return a - b;
+}
+
+struct s {
+ int a, b, c;
+};
+
+static int ko(struct s *a, struct s *b)
+{
+ return a - b;
+}
+
+/*
+ * check-name: ptr-sub-blows
+ * check-command: sparse -Wptr-subtraction-blows $file
+ *
+ * check-error-start
+ptr-sub-blows.c:12:18: warning: potentially expensive pointer subtraction (size = 12 for struct s)
+ * check-error-end
+ */
--
2.16.0
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