[PATCH 11/17] dyndbg: macrofy a 2-index for-loop pattern

Jim Cromie
2026-05-04T20:45:32Z

dynamic-debug currently has 2 __sections (__dyndbg, __dyndb_classes),
struct _ddebug_info keeps track of them both, with 2 members each:
_vec and _vec#_len.

We need to loop over these sections, with index and record pointer,
making ref to both _vec and _vec_len. This is already fiddly and
error-prone, and will get worse as we add a 3rd section.

Lets instead embed/abstract the fiddly-ness in the `for_subvec()`
macro, and avoid repeating it going forward.

This is a for-loop macro expander, so it syntactically expects to
precede either a single statement or a { block } of them, and the
usual typeof or do-while-0 tricks are unavailable to fix the
multiple-expansion warning.

The macro needs a lot from its caller: it needs 2 local vars, 1 of
which is a ref to a contained struct with named members. To support
these requirements, add:

1. __ASSERT_IS_LVALUE(_X):
ie: ((void)sizeof((void)0, &(x)))

2. __ASSERT_HAS_VEC_MEMBERS(_X, _Y):
compile-time check that the _Y "vector" exists
ie: _X->_Y and _X->num_##_Y are lvalues.

The for_subvec() macro then invokes these in the initialization of the
for-loop; they disappear at runtime.

Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
lib/dynamic_debug.c | 27 ++++++++++++++++++++++++---
1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 94a66c8537ab..8f614eba8ace 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -129,6 +129,28 @@ do { \
#define v3pr_info(fmt, ...) vnpr_info(3, fmt, ##__VA_ARGS__)
#define v4pr_info(fmt, ...) vnpr_info(4, fmt, ##__VA_ARGS__)

+/*
+ * simplify a repeated for-loop pattern walking N steps in a T _vec
+ * member inside a struct _box. It expects int i and T *_sp to be
+ * declared in the caller.
+ * @_i: caller provided counter.
+ * @_sp: cursor into _vec, to examine each item.
+ * @_box: ptr to a struct containing @_vec member
+ * @_vec: name of a member in @_box
+ */
+#define __ASSERT_IS_LVALUE(x) ((void)sizeof((void)0, &(x)))
+#define __ASSERT_HAS_VEC_MEMBER(_box, _vec) \
+ (void)sizeof((_box)->_vec + (_box)->num_##_vec)
+
+#define for_subvec(_i, _sp, _box, _vec) \
+ for (__ASSERT_IS_LVALUE(_i), \
+ __ASSERT_IS_LVALUE(_sp), \
+ __ASSERT_HAS_VEC_MEMBER(_box, _vec), \
+ (_i) = 0, \
+ (_sp) = (_box)->_vec; \
+ (_i) < (_box)->num_##_vec; \
+ (_i)++, (_sp)++) /* { block } */
+
static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
{
/* trim any trailing newlines */
@@ -156,7 +178,7 @@ static struct ddebug_class_map *ddebug_find_valid_class(struct ddebug_table cons
struct ddebug_class_map *map;
int i, idx;

- for (map = dt->classes, i = 0; i < dt->num_classes; i++, map++) {
+ for_subvec(i, map, dt, classes) {
idx = match_string(map->class_names, map->length, class_string);
if (idx >= 0) {
*class_id = idx + map->base;
@@ -1232,8 +1254,7 @@ static void ddebug_attach_module_classes(struct ddebug_table *dt, struct _ddebug
* the builtin/modular classmap vector/section. Save the start
* and length of the subrange at its edges.
*/
- for (cm = di->classes, i = 0; i < di->num_classes; i++, cm++) {
-
+ for_subvec(i, cm, di, classes) {
if (!strcmp(cm->mod_name, dt->mod_name)) {
if (!nc) {
v2pr_info("start subrange, class[%d]: module:%s base:%d len:%d ty:%d\n",

--
2.54.0