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

koxudaxi · projectgus · commit 008b8c5181cf · 2025-07-22T12:27:01.000+10:00
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;
Signed-off-by: Angus Gratton &lt;angus@redyak.com.au&gt;
diff --git a/ports/unix/README.md b/ports/unix/README.md
@@ -173,3 +173,7 @@ Several classes of checks are disabled via compiler flags:
   check is intended to make sure locals in a "returned from" stack frame are not
   used. However, this mode interferes with various assumptions that
   MicroPython's stack checking, NLR, and GC rely on.
+
+Note: When building with sanitizers (ASan/UBSan), an 8 KiB stack check margin is
+automatically reserved unless the build overrides MICROPY_STACK_CHECK_MARGIN.
+
diff --git a/ports/unix/mpconfigport.h b/ports/unix/mpconfigport.h
@@ -137,6 +137,19 @@ typedef long mp_off_t;
 #define MICROPY_STACKLESS_STRICT    (0)
 #endif
 
+// Reserve extra C-stack headroom for overflow checks if sanitizers
+// are enabled (sanitizer builds enlarge call frames). 8 KiB prevents
+// false positives without noticeably shrinking usable stack.
+#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 // !defined(MICROPY_STACK_CHECK_MARGIN)
+
 // Implementation of the machine module.
 #define MICROPY_PY_MACHINE_INCLUDEFILE "ports/unix/modmachine.c"
 
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
 
