MicroPython: LVGL asserts cost 44 KB less flash

lv_conf.h

@@ -305,15 +305,24 @@
 #else
     /* On MicroPython a spinning assert locks the scheduler out: USB serial and
      * WebREPL go silent until a power cycle. The MicroPython port's handler
-     * raises RuntimeError naming the function, file and line instead, which
-     * the nearest Python frame or LVGL callback reports, and the board stays
-     * reachable. It is weak here, so a build without it still links and
-     * halts as before. */
+     * raises RuntimeError naming the file and line instead, which the nearest
+     * Python frame or LVGL callback reports, and the board stays reachable.
+     *
+     * LVGL has over a thousand assert sites, so each one is kept to a call
+     * with two arguments: the file's base name and the line, which are
+     * enough to find the assert. The handler doesn't return, so nothing
+     * follows the call. Passing the full path and the function name as well
+     * cost about 50 KB of flash on an ESP32-S3, and with code run from PSRAM
+     * (XIP) it took 128 KB of PSRAM from the heap. */
     #define LV_ASSERT_HANDLER_INCLUDE <stdint.h>
     #if !defined(PYCPARSER) && !defined(__ASSEMBLY__)
-    __attribute__((weak)) void lv_micropython_assert_failed(const char *file, int line, const char *func);
+    __attribute__((noreturn)) void lv_micropython_assert_failed(const char *file, int line);
+    #endif
+    #ifdef __FILE_NAME__
+    #define LV_ASSERT_HANDLER lv_micropython_assert_failed(__FILE_NAME__, __LINE__);
+    #else
+    #define LV_ASSERT_HANDLER lv_micropython_assert_failed(__FILE__, __LINE__);
     #endif
-    #define LV_ASSERT_HANDLER { if (lv_micropython_assert_failed) { lv_micropython_assert_failed(__FILE__, __LINE__, __func__); } while(1); }
 #endif
 
 /*-------------

ports/micropython/src/lv_assert_micropython.c

@@ -6,9 +6,9 @@
  * to spin forever, and on a board that locks the MicroPython scheduler out:
  * USB serial and WebREPL go silent and only a power cycle brings it back.
  *
- * Instead this raises RuntimeError("LVGL assert failed in <function>
- * (<file>:<line>)"). LVGL's log is off in MicroPython builds, so the
- * function and line are how to find the assertion's message in LVGL's source.
+ * Instead this raises RuntimeError("LVGL assert failed at <file>:<line>").
+ * LVGL's log is off in MicroPython builds, so the file and line are how to
+ * find the assertion's message in LVGL's source.
  *
  * Where the exception lands decides what LVGL state needs repair:
  *
@@ -33,7 +33,7 @@
 #include "lvgl/src/display/lv_display_private.h"
 
 
-void lv_micropython_assert_failed(const char *file, int line, const char *func);
+MP_NORETURN void lv_micropython_assert_failed(const char *file, int line);
 
 // From the generated binding: how many Python callbacks LVGL is inside.
 int mp_lv_nesting_depth(void);
@@ -48,8 +48,9 @@ static void lv_micropython_end_pass(void) {
     }
 }
 
-void lv_micropython_assert_failed(const char *file, int line, const char *func) {
-    // Keep only the file's own name. A loop, not strrchr: some ports'
+void lv_micropython_assert_failed(const char *file, int line) {
+    // Keep only the file's own name, for a compiler without __FILE_NAME__
+    // (lv_conf.h passes __FILE__ there). A loop, not strrchr: some ports'
     // C libraries (stm32's) don't provide it.
     const char *base = file;
     for (const char *p = file; *p; p++) {
@@ -60,5 +61,5 @@ void lv_micropython_assert_failed(const char *file, int line, const char *func)
     if (mp_lv_nesting_depth() == 0) {
         lv_micropython_end_pass();
     }
-    mp_raise_msg_varg(&mp_type_RuntimeError, MP_ERROR_TEXT("LVGL assert failed in %s (%s:%d)"), func, base, line);
+    mp_raise_msg_varg(&mp_type_RuntimeError, MP_ERROR_TEXT("LVGL assert failed at %s:%d"), base, line);
 }

tools/test_lvgl_smoke.py

@@ -739,6 +739,32 @@ def test_object_lifetime_and_pointer_validation(lv):
     print("OK: deleted-object and pointer validation")
 
 
+def test_assert_raises(lv, disp):
+    # On MicroPython a failed LVGL assert raises RuntimeError naming the
+    # source file and line, and LVGL keeps working. CircuitPython reboots
+    # into safe mode and CPython halts, so only MicroPython can check it.
+    if _runtime_target() != "micropython":
+        return
+    try:
+        disp.set_tile_cnt(256)  # LVGL asserts tile_cnt < 256
+    except RuntimeError as exc:
+        msg = str(exc)
+    else:
+        _fail("set_tile_cnt(256) returned instead of raising")
+    prefix = "LVGL assert failed at lv_display.c:"
+    if not msg.startswith(prefix) or not msg[len(prefix):].isdigit():
+        _fail("unexpected assert message: {}".format(msg))
+    if disp.get_tile_cnt() >= 256:
+        _fail("the asserting call changed the display")
+    label = lv.label(lv.screen_active())
+    label.set_text("after assert")
+    lv.refr_now(disp)
+    if label.get_text() != "after assert":
+        _fail("LVGL stopped working after an assert")
+    label.delete()
+    print("OK: an LVGL assert raises RuntimeError at file:line and LVGL carries on")
+
+
 def test_target_exceptions(lv):
     # LV_USE_TJPGD is 0 on every target: the JPEG decoder is jpegio's,
     # registered via lv_image_decoder_create by displayif, the CircuitPython
@@ -773,6 +799,7 @@ def main():
             test_refr_now(lv, disp)
             test_pointer_buffer_dereference(lv, disp)
         test_widget(lv)
+        test_assert_raises(lv, disp)
         test_struct_fields_and_arrays(lv)
         test_line_points_list_and_buffer(lv)
         test_struct_array_fields(lv)