0001-proof-of-concept-mpy-cross-mno-long.patch

From 7188d09390183a4333562fcb6bba7f93b85d5ac4 Mon Sep 17 00:00:00 2001
From: Jeff Epler <[email protected]>
Date: Mon, 9 Dec 2024 18:06:17 -0600
Subject: [PATCH] proof of concept: mpy-cross -mno-long

This causes an OverflowError to be raised if an integer constant doesn't
fit on builds without long int support.

Hypothetically, circuitpython-build-tools could first run mpy-cross with
this flag; if it fails, put into some new metadata file "requires
long integers" and run again without the flag.
---
 mpy-cross/main.c    |  3 +++
 py/mpstate.h        |  1 +
 py/persistentcode.c | 26 ++++++++++++++++++++++++++
 3 files changed, 30 insertions(+)

diff --git a/mpy-cross/main.c b/mpy-cross/main.c
index 611da76468..83913f33e8 100644
--- a/mpy-cross/main.c
+++ b/mpy-cross/main.c
@@ -274,6 +274,9 @@ MP_NOINLINE int main_(int argc, char **argv) {
                 }
                 a += 1;
                 source_file = backslash_to_forwardslash(argv[a]);
+            } else if (strcmp(argv[a], "-mno-long") == 0) {
+                mp_printf(&mp_plat_print, "no-long");
+                mp_dynamic_compiler.no_long_int = true;
             } else if (strncmp(argv[a], "-msmall-int-bits=", sizeof("-msmall-int-bits=") - 1) == 0) {
                 char *end;
                 mp_dynamic_compiler.small_int_bits =
diff --git a/py/mpstate.h b/py/mpstate.h
index 7308e57b58..f1709b68b5 100644
--- a/py/mpstate.h
+++ b/py/mpstate.h
@@ -74,6 +74,7 @@ typedef struct mp_dynamic_compiler_t {
     uint8_t small_int_bits; // must be <= host small_int_bits
     uint8_t native_arch;
     uint8_t nlr_buf_num_regs;
+    bool no_long_int;
 } mp_dynamic_compiler_t;
 extern mp_dynamic_compiler_t mp_dynamic_compiler;
 #endif
diff --git a/py/persistentcode.c b/py/persistentcode.c
index 09beeef451..ae69f99dea 100644
--- a/py/persistentcode.c
+++ b/py/persistentcode.c
@@ -69,6 +69,7 @@ typedef struct _bytecode_prelude_t {
 
 #include "py/parsenum.h"
 
+}
 static int read_byte(mp_reader_t *reader);
 static size_t read_uint(mp_reader_t *reader);
 
@@ -476,6 +477,30 @@ void mp_raw_code_load_file(qstr filename, mp_compiled_module_t *context) {
 
 #include "py/objstr.h"
 
+static void small_int_check(mp_obj_t o) {
+    #if MICROPY_DYNAMIC_COMPILER
+    if (!mp_dynamic_compiler.no_long_int) {
+        return;
+    }
+    if (!mp_obj_is_int(o)) {
+        return;
+    }
+    bool fail = false;
+    if (!mp_obj_is_small_int(o)) {
+        fail = true;
+    } else {
+        mp_int_t arg = MP_OBJ_SMALL_INT_VALUE(o);
+        mp_uint_t sign_mask = -((mp_uint_t)1 << (mp_dynamic_compiler.small_int_bits - 1));
+        if (!((arg & sign_mask) == 0 || (arg & sign_mask) == sign_mask)) {
+            fail = true;
+        }
+    }
+    if (fail) {
+        mp_raise_type(&mp_type_OverflowError);
+    }
+    #endif
+}
+
 static void mp_print_bytes(mp_print_t *print, const byte *data, size_t len) {
     print->print_strn(print->data, (const char *)data, len);
 }
@@ -551,6 +576,7 @@ static void save_obj(mp_print_t *print, mp_obj_t o) {
         byte obj_type;
         if (mp_obj_is_int(o)) {
             obj_type = MP_PERSISTENT_OBJ_INT;
+            small_int_check(o);
         #if MICROPY_PY_BUILTINS_COMPLEX
         } else if (mp_obj_is_type(o, &mp_type_complex)) {
             obj_type = MP_PERSISTENT_OBJ_COMPLEX;
-- 
2.39.5