Description
Port, board and/or hardware
Windows x64
MicroPython version
MicroPython v1.26.0-preview.265.gd134cdb9a3.dirty build-vs (x64, Debug, dev, 2017)
Reproduction
- Enable sys_settrace in a windows build
- run a program that prints a frame object
Expected behaviour
The frame object can be printed.
Observed behaviour
Frequently, this will cause an assertion error, as it did in this run of #17538 which adds a test of frame object printing.
Run python run-tests.py --print-failures
--- D:/a/micropython/micropython/tests/results\misc_sys_settrace_cov.py.exp 2025-06-20 18:41:30.413152600 +0000
+++ D:/a/micropython/micropython/tests/results\misc_sys_settrace_cov.py.out 2025-06-20 18:41:30.413152600 +0000
@@ -1,2 +1,2 @@
-FRAME <frame at 0x\[0-9a-f\]\+, file 'misc/sys_settrace_repr\.py', line \\d\+, code f>
-LASTI \\d\+
+FRAME <frame at 0xe06df4a0, file 'D:/a/micropython/micropython/tests/misc/sys_settrace_cov.py', line 20, code Assertion failed: *q < pool->len, file d:\a\micropython\micropython\py\qstr.c, line 198
+CRASH
\ No newline at end of file
FAILURE D:/a/micropython/micropython/tests/results\misc_sys_settrace_cov.py```
### Additional Information
I think there is a pervasive problem with %q in format strings depending on undefined behavior, at least on systems where sizeof(intptr_t) != sizeof(int).
Take for example this line in `objtype.c`:
```c
mp_printf(print, "<class '%q'>", self->name);
The type of the expression self->name is uint16_t. when it is passed through ... it is promoted according to "default argument promotions". On all platforms of interest, I think this means that it is promoted to int.
In mp_vprintf, it is retrieved with a type of size_t, due to typedef size_t qstr in qstr.h:
case 'q': {
qstr qst = va_arg(args, qstr);However, on platforms like x64 windows ("LP64"), these are two distinct integer types of different size.
In practice, the actual argument passing practice of msvc prevents an overt misbehavior in many cases, except for this one in the frame printing code for sys_settrace with one specific msvc version.
The same problem would affect I16LP32 ports. I encountered this trying to create an I16LP32 port based on m68k where the problem seems to affect just about any use of %q with an int16 argument. for example, the int object is unprintable in the repl due to this.
Code of Conduct
Yes, I agree