Modular•2mo ago

Segmentation Fault Core dumped

Been hard stucking on running the follow function as binary in Linux. It can run by mojo run .mojo just fine but it just can’t be executed as a binary … and the only error I got is in the title.

fn get_codewords(owned padded: List[Int]) -> List[Int]:
    var ecwords = List[Int](0)*64
    var values = List[Int]()

    for i in range(222):
        var temp: Int = (padded[i] + ecwords[0]) % 929
        for j in range(63, -1, -1):
            var val: Int = temp * EC_LV5[j] % 929
            var factor: Int = ecwords[64-j] if j > 0 else 0
            ecwords[63-j] = (factor + 929 - val) % 929

    return ecwords

fn get_codewords(owned padded: List[Int]) -> List[Int]:
    var ecwords = List[Int](0)*64
    var values = List[Int]()

    for i in range(222):
        var temp: Int = (padded[i] + ecwords[0]) % 929
        for j in range(63, -1, -1):
            var val: Int = temp * EC_LV5[j] % 929
            var factor: Int = ecwords[64-j] if j > 0 else 0
            ecwords[63-j] = (factor + 929 - val) % 929

    return ecwords

EC_LV5 is 64 bytes of error correction codewords ECL_LV5 = ListInt

16 Replies

sb•2mo ago

Do you have any way of putting this in gdb at the moment? We can try to tease apart where things might be falling over

benny•2mo ago

what is the intended value of ecwords?

randomasiandude•2mo ago

output value is correct . A list of 64 elements values from 0-929

sb•2mo ago

are you able to run any of this in GDB or some other debugger?

randomasiandude•2mo ago

I’ve only tested in Ubuntu terminal and vscode

sora•2mo ago

Could you share the full script?

randomasiandude•2mo ago

I can run the fn without any issue I couldn’t run it in binary execution form

sb•2mo ago

Yeah, can in the ubuntu VM/wsl can you install gdb?

randomasiandude•2mo ago

Like ./test I’ll try right now Not VM not WSL Ubuntu OS I’ll provide result in few mins

This GDB supports auto-downloading debuginfo from the following URLs:
  <https://debuginfod.ubuntu.com>
Enable debuginfod for this session? (y or [n]) y
Debuginfod has been enabled.
To make this setting permanent, add 'set debuginfod enabled on' to .gdbinit.
Downloading separate debug info for system-supplied DSO at 0x7ffff7fc3000
Downloading separate debug info for /lib/x86_64-linux-gnu/libstdc++.so.6        
Downloading separate debug info for /lib/x86_64-linux-gnu/libgcc_s.so.1         
[Thread debugging using libthread_db enabled]                                   
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7ffff6e006c0 (LWP 11477)]
[New Thread 0x7ffff64006c0 (LWP 11478)]
[New Thread 0x7ffff5a006c0 (LWP 11479)]
[New Thread 0x7ffff50006c0 (LWP 11480)]
[New Thread 0x7ffff46006c0 (LWP 11481)]

Thread 1 "errc" received signal SIGSEGV, Segmentation fault.
0x000055555555bf6c in main ()

This GDB supports auto-downloading debuginfo from the following URLs:
  <https://debuginfod.ubuntu.com>
Enable debuginfod for this session? (y or [n]) y
Debuginfod has been enabled.
To make this setting permanent, add 'set debuginfod enabled on' to .gdbinit.
Downloading separate debug info for system-supplied DSO at 0x7ffff7fc3000
Downloading separate debug info for /lib/x86_64-linux-gnu/libstdc++.so.6        
Downloading separate debug info for /lib/x86_64-linux-gnu/libgcc_s.so.1         
[Thread debugging using libthread_db enabled]                                   
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7ffff6e006c0 (LWP 11477)]
[New Thread 0x7ffff64006c0 (LWP 11478)]
[New Thread 0x7ffff5a006c0 (LWP 11479)]
[New Thread 0x7ffff50006c0 (LWP 11480)]
[New Thread 0x7ffff46006c0 (LWP 11481)]

Thread 1 "errc" received signal SIGSEGV, Segmentation fault.
0x000055555555bf6c in main ()

I somehow fixed it by putting var ECL_V5 from outside of the fn into inside of the fn…. Still don’t know what’s the actual reason behind

sb•2mo ago

can you maybe add -g or something to the compiler flags? need debug symbols to diagnose

randomasiandude•2mo ago

I discovered that if a variable is outside of the fn it should be defined as alias not var in order to make the binary work. If its defined as var the script can still run with mojo run

ModularBot•2mo ago

Congrats @randomasiandude, you just advanced to level 1!

randomasiandude•2mo ago

Thank you for the gdb knowledge which I didn’t know 🙂 The issue was about defining global variables/constants as var vs. as alias . In my case it needs to be defined as alias for the binary to work As a dude from python took me a while to figure out. And still reading the variables scope thing

sb•2mo ago

interesting! weird that caused a segfault though? I forget if global vars are supported yet or not

Ryulord•2mo ago

they're not currently supported and the segfault on attempting to use one is a known bug. There probably should be a warning from the lsp and a mention in the 'sharp edges' page

randomasiandude•2mo ago

Very True, especially for new comers from python.

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Segmentation Fault Core dumped