test/argparse: change initialization to workaround LTO

When compiled with Link Time Optimization, the existing code
generated an error, because the compiler was unable to intuit
that there was space in the flexible array.

In function ‘test_argparse_copy’,
    inlined from ‘test_argparse_init_obj’
        at ../app/test/test_argparse.c:108:2,
    inlined from ‘test_argparse_opt_callback_parse_int_of_no_val’
        at ../app/test/test_argparse.c:490:8:
../app/test/test_argparse.c:96:17: warning:
‘memcpy’ writing 56 bytes into a region of size 0 overflows the destination
        memcpy(&dst->args[i], &src->args[i], sizeof(src->args[i]));

Initializing a structure with flexible array is special case
and compiler expands the structure to fit.
But inside the copy function it no longer knew that.

The workaround is to put the copy inside the same function
and use structure assignment. Also macro should be upper case.

Fixes: 6c5c657 ("argparse: verify argument config")
Cc: [email protected]

Signed-off-by: Stephen Hemminger <[email protected]>
Acked-by: Bruce Richardson <[email protected]>
Acked-by: Chengwen Feng <[email protected]>

Author: shemminger

app/test/test_argparse.c

@@ -72,7 +72,7 @@ test_argparse_callback(uint32_t index, const char *value, void *opaque)
 }
 
 /* valid templater, must contain at least two args. */
-#define argparse_templater() { \
+#define ARGPARSE_TEMPLATE { \
 	.prog_name = "test_argparse", \
 	.usage = "-a xx -b yy", \
 	.descriptor = NULL, \
@@ -88,25 +88,24 @@ test_argparse_callback(uint32_t index, const char *value, void *opaque)
 	}, \
 }
 
-static void
-test_argparse_copy(struct rte_argparse *dst, struct rte_argparse *src)
-{
-	uint32_t i;
-	memcpy(dst, src, sizeof(*src));
-	for (i = 0; /* NULL */; i++) {
-		memcpy(&dst->args[i], &src->args[i], sizeof(src->args[i]));
-		if (src->args[i].name_long == NULL)
-			break;
-	}
-}
 
 static struct rte_argparse *
 test_argparse_init_obj(void)
 {
-	static struct rte_argparse backup = argparse_templater();
-	static struct rte_argparse obj = argparse_templater();
-	/* Because obj may be overwritten, do a deep copy. */
-	test_argparse_copy(&obj, &backup);
+	/* Note: initialization of structure with flexible array
+	 * increases the size of the variable to match.
+	 */
+	static const struct rte_argparse backup = ARGPARSE_TEMPLATE;
+	static struct rte_argparse obj = ARGPARSE_TEMPLATE;
+	unsigned int i;
+
+	obj = backup;
+	for (i = 0; ; i++) {
+		obj.args[i] = backup.args[i];
+		if (backup.args[i].name_long == NULL)
+			break;
+	}
+
 	return &obj;
 }