printing to io.StringIO subclass leads to seg fault
I'm aware that MicroPython io documentation says
Note that for efficiency, MicroPython doesn’t provide abstract base classes corresponding to the hierarchy above, and it’s not possible to implement, or subclass, a stream class in pure Python.
Minimal example to reproduce test_stream.py:
import io
class TestStream(io.StringIO):
def __init_(self, alloc_size):
super().__init__(alloc_size)
test = TestStream(100)
print("Now the seg fault...")
print("hello", file=test)
$ micropython test_stream.py
Now the seg fault...
Segmentation fault: 11
But I would expect an Exception if this is not possible not a crash/seg fault.
I was able to reproduce this in unix(MacOS) and stm32(pybV1.1) ports.
Maybe is related to #1067?
I had a look at py/mpprint.c but I cannot see any hint... Is there any tool to debug these types of crashes?
This is the valgrind output:
==20210== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==20210== Using Valgrind-3.19.0.GIT-lbmacos and LibVEX; rerun with -h for copyright info
==20210== Command: micropython test_stream.py
==20210==
==20210== Warning: set address range perms: large range [0x7fff201b6000, 0x80001ffb6000) (defined)
==20210== Warning: set address range perms: large range [0x7fff201b6000, 0x7fff7fb4a000) (defined)
==20210== Warning: set address range perms: large range [0x7fff8e41a000, 0x7fffc01b6000) (noaccess)
==20210== Warning: set address range perms: large range [0x7fffc01b6000, 0x7fffe307a000) (defined)
==20210== Warning: set address range perms: large range [0x7fffe307a000, 0x7fffffe00000) (noaccess)
Now the seg fault...
==20210== Invalid read of size 1
==20210== at 0x10002C057: ??? (in /usr/local/bin/micropython)
==20210== by 0x10002E711: ??? (in /usr/local/bin/micropython)
==20210== by 0x10002E7DB: ??? (in /usr/local/bin/micropython)
==20210== by 0x10002BB4F: ??? (in /usr/local/bin/micropython)
==20210== by 0x100030D6F: ??? (in /usr/local/bin/micropython)
==20210== by 0x100023DF5: ??? (in /usr/local/bin/micropython)
==20210== by 0x100034D18: ??? (in /usr/local/bin/micropython)
==20210== by 0x100023FDE: ??? (in /usr/local/bin/micropython)
==20210== by 0x100078425: machine_time_pulse_us (in /usr/local/bin/micropython)
==20210== by 0x100077DD4: machine_time_pulse_us (in /usr/local/bin/micropython)
==20210== by 0x7FFF204DFF3C: ??? (in /dev/ttys016)
==20210== by 0x1: ???
==20210== Address 0x19 is not stack'd, malloc'd or (recently) free'd
==20210==
==20210==
==20210== Process terminating with default action of signal 11 (SIGSEGV)
==20210== Access not within mapped region at address 0x19
==20210== at 0x10002C057: ??? (in /usr/local/bin/micropython)
==20210== by 0x10002E711: ??? (in /usr/local/bin/micropython)
==20210== by 0x10002E7DB: ??? (in /usr/local/bin/micropython)
==20210== by 0x10002BB4F: ??? (in /usr/local/bin/micropython)
==20210== by 0x100030D6F: ??? (in /usr/local/bin/micropython)
==20210== by 0x100023DF5: ??? (in /usr/local/bin/micropython)
==20210== by 0x100034D18: ??? (in /usr/local/bin/micropython)
==20210== by 0x100023FDE: ??? (in /usr/local/bin/micropython)
==20210== by 0x100078425: machine_time_pulse_us (in /usr/local/bin/micropython)
==20210== by 0x100077DD4: machine_time_pulse_us (in /usr/local/bin/micropython)
==20210== by 0x7FFF204DFF3C: ??? (in /dev/ttys016)
==20210== by 0x1: ???
==20210== If you believe this happened as a result of a stack
==20210== overflow in your program's main thread (unlikely but
==20210== possible), you can try to increase the size of the
==20210== main thread stack using the --main-stacksize= flag.
==20210== The main thread stack size used in this run was 8388608.
==20210==
==20210== HEAP SUMMARY:
==20210== in use at exit: 0 bytes in 0 blocks
==20210== total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==20210==
==20210== All heap blocks were freed -- no leaks are possible
==20210==
==20210== For lists of detected and suppressed errors, rerun with: -s
==20210== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
Segmentation fault: 11
Not sure if this helps...
docs: How to use io module
Hey, I'm using micropython 1.20 with a generic esp32 devkit board. I have read the io module documentation and I dont understand how it work.
First: It seems like it doesnt matter the argument passed to the io.StringIO class:
import io
a = io.StringIO(1)
a.write("hola")
I would expect this operation to fail because the buffer should be size 1, but not only it doesnt fail, but I was able to allocate the whole word and print it using a.getvalue().
Second: Why the a.read() is just printing an empty string? It seems I can use the write() method but I cant use the read() method. Altough I wa able to get the value inside the buffer using the getvalue() method.
Third: How can I flush the buffer? Seems like the flush() do not work. I'm using it like this:
import io
a = io.StringIO(1)
a.write("hola")
a.flush()
print(a.getvalue())
But this prints the "hola".
Thanks in advance for any answers to my questions. And if there is way to update the docs in https://docs.micropython.org I could work on that,