feat(core): add lv_check_arg to public functions in lv_observer

[axos88]

Summary

Add LV_CHECK_ARG guards to previously unguarded parameters in public API functions in src/core/lv_observer.c. This PR adds parameter validation to 7 functions and fixes 1 validation issue.

Functions modified

Function	Parameter	Action	Reason
void lv_subject_init_int(lv_subject_t * subject, int32_t value)	subject	Added	Dereferenced directly
	value	No check needed	Integer, any value valid
void lv_subject_init_string(lv_subject_t * subject, char * buf, char * tmp_buf, uint32_t size, const char * value)	subject	Added	Dereferenced directly
	buf	Added	Passed to lv_strlcpy directly
	size	Added	size == 0 makes subject permanently unusable
	value	Added	Passed to lv_strlcpy directly

Generated with Claude Code

[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

[github-actions]

Hi 👋, thank you for your PR!

We've run benchmarks in an emulated environment. Here are the results:

ARM Emulated 32b - lv_conf_perf32b

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)	Flush Time (ms)
All scenes avg.	36	35	10	10	0

Detailed Results Per Scene

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)	Flush Time (ms)
Empty screen	11	33	0	0	0
Moving wallpaper	5	33	1	1	0
Single rectangle	0	50	0	0	0
Multiple rectangles	0	33	0	0	0
Multiple RGB images	0	38	0	0	0
Multiple ARGB images	22	33	7	7	0
Rotated ARGB images	61	46	16	16	0
Multiple labels	40 (+3)	34 (+1)	10	10	0
Screen sized text	86 (-3)	46	18	18	0
Multiple arcs	44	36	9	9	0
Containers	10 (+2)	38 (+1)	0	0	0
Containers with overlay	88	20	46	46	0
Containers with opa	23 (-2)	38 (+1)	2	2	0
Containers with opa_layer	25 (+3)	36	7 (+1)	7 (+1)	0
Containers with scrolling	98	36	24	24	0
Widgets demo	74 (-2)	20	22 (-1)	22 (-1)	0
All scenes avg.	36	35	10	10	0

ARM Emulated 64b - lv_conf_perf64b

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)	Flush Time (ms)
All scenes avg.	35 (+1)	35	9	9	0

Detailed Results Per Scene

Scene Name	Avg CPU (%)	Avg FPS	Avg Time (ms)	Render Time (ms)	Flush Time (ms)
Empty screen	11	33	0	0	0
Moving wallpaper	2	33	1	1	0
Single rectangle	0	50	0	0	0
Multiple rectangles	0	33	0	0	0
Multiple RGB images	0	35	0	0	0
Multiple ARGB images	20	33	7	7	0
Rotated ARGB images	30	33	9	9	0
Multiple labels	60	46	10	10	0
Screen sized text	87	46	18	18	0
Multiple arcs	49	40	7	7	0
Containers	7	38 (-1)	0	0	0
Containers with overlay	90	21	43	43	0
Containers with opa	19 (+12)	37 (+1)	1	1	0
Containers with opa_layer	23	35 (-2)	7	7	0
Containers with scrolling	97 (-1)	38	23 (+1)	23 (+1)	0
Widgets demo	74	22	20	20	0
All scenes avg.	35 (+1)	35	9	9	0

Disclaimer: These benchmarks were run in an emulated environment using QEMU with instruction counting mode.
The timing values represent relative performance metrics within this specific virtualized setup and should
not be interpreted as absolute real-world performance measurements. Values are deterministic and useful for
comparing different LVGL features and configurations, but may not correlate directly with performance on
physical hardware. The measurements are intended for comparative analysis only.

---

🤖 This comment was automatically generated by a bot.

[cubic-dev-ai]

1 issue found across 1 file

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="src/core/lv_observer.c">

<violation number="1" location="src/core/lv_observer.c:512">
P2: Allowing `subject == NULL` here opens a path where `lv_obj_remove_event_cb_with_user_data(obj, NULL, subject)` becomes `...user_data == NULL`, which can remove unrelated callbacks from the widget.

(Based on your team's feedback about documented NULL semantics for `lv_obj_remove_from_subject`.) [FEEDBACK_USED]</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

P2: Allowing subject == NULL here opens a path where lv_obj_remove_event_cb_with_user_data(obj, NULL, subject) becomes ...user_data == NULL, which can remove unrelated callbacks from the widget.

(Based on your team's feedback about documented NULL semantics for lv_obj_remove_from_subject.)

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At src/core/lv_observer.c, line 512:

<comment>Allowing `subject == NULL` here opens a path where `lv_obj_remove_event_cb_with_user_data(obj, NULL, subject)` becomes `...user_data == NULL`, which can remove unrelated callbacks from the widget.

(Based on your team's feedback about documented NULL semantics for `lv_obj_remove_from_subject`.) </comment>

<file context>
@@ -502,7 +509,8 @@ void lv_observer_remove(lv_observer_t * observer)
 {
     LV_CHECK_ARG(obj != NULL, return);
-    LV_CHECK_ARG(subject != NULL, return);
+    /* subject == NULL is documented as valid: remove from ALL subjects */
+
     /*
</file context>