dev/cppcheck: add minimal reproducer for memleakOnRealloc false positive

dev/cppcheck/cppcheck_test.c

@@ -0,0 +1,65 @@
+/*
+ * Minimal reproducer for a cppcheck false positive.
+ *
+ * cppcheck incorrectly reports a memory leak for the pattern below.
+ * The pointer <local_ptr> is a local copy of <buf->ptr>. When realloc()
+ * fails and returns NULL, <local_ptr> becomes NULL, but the original
+ * allocation is still referenced by <buf->ptr>. The failure branch then
+ * uses <buf->ptr> to properly free the original memory, so there is no
+ * real leak.
+ *
+ * Reference: https://www.mail-archive.com/haproxy@formilux.org/msg46968.html
+ * Origin:    src/quic_rx.c, function qc_try_store_new_token()
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+struct buf {
+	char   *ptr;
+	size_t  len;
+};
+
+static inline char *buf_ptr(struct buf b) { return b.ptr; }
+static inline size_t buf_len(struct buf b) { return b.len; }
+static inline void buf_free(struct buf *b) { free(b->ptr); b->ptr = NULL; b->len = 0; }
+
+/* Update the raw-byte buffer <b> with <data> of length <len>, reallocating
+ * when needed.  The buffer stores raw bytes; no null terminator is appended.
+ *
+ * False positive: cppcheck may report a memleak at the realloc() line because
+ * it sees <local_ptr> (a local variable) overwritten with the NULL return value
+ * of realloc() and concludes the original allocation is lost.  In reality the
+ * original pointer is preserved in <b->ptr> and properly freed in the else
+ * branch, so no leak can occur.
+ */
+static void update_buf(struct buf *b, const char *data, size_t len)
+{
+	char *local_ptr;
+
+	local_ptr = buf_ptr(*b);
+	if (len > buf_len(*b)) {
+		local_ptr = realloc(local_ptr, len);
+		if (local_ptr)
+			b->ptr = local_ptr;
+		else {
+			memset(buf_ptr(*b), 0, buf_len(*b));
+			buf_free(b);
+		}
+	}
+
+	if (local_ptr) {
+		memcpy(local_ptr, data, len);
+		b->len = len;
+	}
+}
+
+int main(void)
+{
+	struct buf b = { NULL, 0 };
+
+	update_buf(&b, "hello", 5);
+	update_buf(&b, "world!", 6);
+	buf_free(&b);
+	return 0;
+}

src/cpuset.c

@@ -28,6 +28,8 @@ int ha_cpuset_set(struct hap_cpuset *set, int cpu)
 	set->cpuset |= (0x1 << cpu);
 	return 0;
 #endif
+
+	return 1;
 }
 
 int ha_cpuset_clr(struct hap_cpuset *set, int cpu)
@@ -43,6 +45,8 @@ int ha_cpuset_clr(struct hap_cpuset *set, int cpu)
 	set->cpuset &= ~(0x1 << cpu);
 	return 0;
 #endif
+
+	return 1;
 }
 
 void ha_cpuset_and(struct hap_cpuset *dst, struct hap_cpuset *src)
@@ -97,6 +101,8 @@ int ha_cpuset_count(const struct hap_cpuset *set)
 #elif defined(CPUSET_USE_ULONG)
 	return my_popcountl(set->cpuset);
 #endif
+
+	return 0;
 }
 
 int ha_cpuset_ffs(const struct hap_cpuset *set)
@@ -121,6 +127,8 @@ int ha_cpuset_ffs(const struct hap_cpuset *set)
 
 	return my_ffsl(set->cpuset);
 #endif
+
+	return 0;
 }
 
 void ha_cpuset_assign(struct hap_cpuset *dst, struct hap_cpuset *src)
@@ -149,6 +157,8 @@ int ha_cpuset_isequal(const struct hap_cpuset *dst, const struct hap_cpuset *src
 #elif defined(CPUSET_USE_ULONG)
 	return dst->cpuset == src->cpuset;
 #endif
+
+	return 0;
 }
 
 int ha_cpuset_size()
@@ -160,6 +170,8 @@ int ha_cpuset_size()
 	return LONGBITS;
 
 #endif
+
+	return 0;
 }
 
 /* Parse cpu sets. Each CPU set is either a unique number between 0 and