build/sanitizer: Reserve 8 KiB C-stack margin for sanitizer builds.

koxudaxi · koxudaxi · commit d1ff01dbb643 · 2025-07-10T03:42:45.000+09:00
Compiler sanitizers such as AddressSanitizer and UndefinedSanitizer
inflate call frames and can trip MicroPython's C-stack overflow check.
Define MICROPY_STACK_CHECK_MARGIN = 8192 when the relevant sanitizer
macros are present, update the unix port config, docs, and the
thread_stacksize test.  Non-sanitizer builds are unchanged.

Signed-off-by: Koudai Aono &lt;koxudaxi@gmail.com&gt;
diff --git a/docs/library/micropython.rst b/docs/library/micropython.rst
@@ -80,6 +80,9 @@ Functions
    used.  The absolute value of this is not particularly useful, rather it
    should be used to compute differences in stack usage at different points.
 
+   Note: When building with sanitizers (ASan/UBSan), an 8 KiB stack margin is
+   automatically reserved unless the port overrides MICROPY_STACK_CHECK_MARGIN.
+
 .. function:: heap_lock()
 .. function:: heap_unlock()
 .. function:: heap_locked()
diff --git a/ports/unix/mpconfigport.h b/ports/unix/mpconfigport.h
@@ -137,6 +137,11 @@ typedef long mp_off_t;
 #define MICROPY_STACKLESS_STRICT    (0)
 #endif
 
+// Reserve extra C-stack headroom for overflow checks.
+// Sanitizer builds enlarge call frames; 8 KiB prevents
+// false positives without noticeably shrinking usable stack.
+#define MICROPY_STACK_CHECK_MARGIN  (8192)
+
 // Implementation of the machine module.
 #define MICROPY_PY_MACHINE_INCLUDEFILE "ports/unix/modmachine.c"
 
diff --git a/py/mpconfig.h b/py/mpconfig.h
@@ -701,6 +701,16 @@
 // Additional margin between the places in the runtime where Python stack is
 // checked and the actual end of the C stack. Needs to be large enough to avoid
 // overflows from function calls made between checks.
+#if !defined(MICROPY_STACK_CHECK_MARGIN)
+#if defined(__SANITIZE_ADDRESS__) || defined(__SANITIZE_UNDEFINED__)
+#define MICROPY_STACK_CHECK_MARGIN (8192)
+#elif defined(__has_feature)
+#if __has_feature(address_sanitizer) || __has_feature(undefined_sanitizer)
+#define MICROPY_STACK_CHECK_MARGIN (8192)
+#endif
+#endif
+#endif
+
 #ifndef MICROPY_STACK_CHECK_MARGIN
 #define MICROPY_STACK_CHECK_MARGIN (0)
 #endif
diff --git a/tests/thread/thread_stacksize1.py b/tests/thread/thread_stacksize1.py
@@ -7,7 +7,11 @@
 
 # different implementations have different minimum sizes
 if sys.implementation.name == "micropython":
-    sz = 2 * 1024
+    # Use larger stack size for desktop platforms to accommodate sanitizers
+    if sys.platform in ("linux", "darwin", "emscripten", "win32"):
+        sz = 32 * 1024
+    else:
+        sz = 2 * 1024
 else:
     sz = 512 * 1024
 
