[Help wanted] Evaluating optional argument to not None gives segmentation fault

[kraudy]

Issue description

I have a class that needs an optional argument. When evaluating to None, it gives an error. If evaluating to None gives an error, how am i supposed to evaluate it? But also, i may be doing something wrong.

struct Value:
    var data: UnsafePointer[Float32]
    var _prev3 : List[UnsafePointer[Value]]

    fn __init__(out self, data: Float32,
                        _children2: Optional[List[UnsafePointer[Value]]] = None
                        :
        
        self.data = UnsafePointer[Scalar[DType.float32]].alloc(1)
        self.data.store(data)

        if _children2 is not None:
            self._prev3 = UnsafePointer[Value].alloc(len(_children2.value()))

            for i in range(len(_children2.value())):
                self._prev3[i] = _children2.value()[i]
        else:
            self._prev3 = UnsafePointer[Value].alloc(0)

Steps to reproduce

Bash output

[42727:42727:20250115,205605.282809:ERROR file_io_posix.cc:144] open /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq: No such file or directory (2)
[42727:42727:20250115,205605.282897:ERROR file_io_posix.cc:144] open /sys/devices/system/cpu/cpu0/cpufreq/scaling_max_freq: No such file or directory (2)
Please submit a bug report to https://github.com/modularml/mojo/issues and include the crash backtrace along with all the relevant source codes.
Stack dump:
0.      Program arguments: mojo engine.mojo
#0 0x00005568f231a6bb llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) Signals.cpp:0:0
#1 0x00005568f2318619 llvm::sys::RunSignalHandlers() Signals.cpp:0:0
#2 0x00005568f231ad3d SignalHandler(int) Signals.cpp:0:0
#3 0x00007f5c68f6c520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
#4 0x00007f5c645146ba KGEN_CompilerRT_AsyncRT_CreateRuntime (/home/kraudy/Mojo/mojo-learn/.magic/envs/default/lib/libKGENCompilerRTShared.so+0x146ba)
#5 0x00007ffd8e3f0848 
mojo crashed!
Please file a bug report.
Segmentation fault

Debug output

3
loc(" -> !kgen.none>>":1:2): error: expected non-function type
loc("union<struct<() memoryOnly>, struct<(pointer<none>, index, index) memoryOnly>>, scalar<ui8>)>":1:1): error: expected non-function type
loc(" memoryOnly>, struct<(pointer<none>, index, index) memoryOnly>>":1:2): error: expected non-function type
src/tcmalloc.cc:302] Attempt to free invalid pointer 0x7ffff7c1c5ac 
error: libc.so.6 0x002032e6: DW_TAG_member '__padding' refers to type 0x00000000002032f3 which extends beyond the bounds of 0x002032ce
error: libc.so.6 0x00202b98: DW_TAG_member 'unwind_exception_align' refers to type 0x0000000000202ba6 which extends beyond the bounds of 0x00202b89
error: libc.so.6 0x00202f86: DW_TAG_member 'pad' refers to type 0x0000000000202f9f which extends beyond the bounds of 0x00202f7d
Please submit a bug report to https://github.com/modularml/mojo/issues and include the crash backtrace along with all the relevant source codes.
Stack dump:
0.	Program arguments: /home/kraudy/.vscode-server/data/User/globalStorage/modular-mojotools.vscode-mojo/magic-data-home/envs/max/bin/mojo run --no-optimization --debug-level full /home/kraudy/Mojo/mojo-grad/mojograd/engine.mojo
 #0 0x000055555ac996bb llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) Signals.cpp:0:0
 #1 0x000055555ac97619 llvm::sys::RunSignalHandlers() Signals.cpp:0:0
 #2 0x000055555ac99d3d SignalHandler(int) Signals.cpp:0:0
 #3 0x00007ffff7907520 (/lib/x86_64-linux-gnu/libc.so.6+0x42520)
 #4 0x00007ffff795b9fc __pthread_kill_implementation ./nptl/./nptl/pthread_kill.c:44:76
 #5 0x00007ffff795b9fc __pthread_kill_internal ./nptl/./nptl/pthread_kill.c:78:10
 #6 0x00007ffff795b9fc pthread_kill ./nptl/./nptl/pthread_kill.c:89:10
 #7 0x00007ffff7907476 gsignal ./signal/../sysdeps/posix/raise.c:27:6
 #8 0x00007ffff78ed7f3 abort ./stdlib/./stdlib/abort.c:81:7
 #9 0x00007ffff7df513b tcmalloc::Log(tcmalloc::LogMode, char const*, int, tcmalloc::LogItem, tcmalloc::LogItem, tcmalloc::LogItem, tcmalloc::LogItem) internal_logging.cc:0:0
#10 0x00007ffff7def89a (anonymous namespace)::InvalidFree(void*) tcmalloc.cc:0:0
#11 0x00007fff840165bb 
mojo crashed!
Please file a bug report.
Process 42859 exited with status = 6 (0x00000006) 

[zyx-billy]

Hi, can you provide a minimal repro for this? That way we can see how the function's called and repro it on our side. Thanks!