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Sdl2Application crash if passed arguments with equal sign (--flag=value) #305

helmesjo opened this issue Jan 9, 2019 · 3 comments


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helmesjo commented Jan 9, 2019

So, basically what the title says:
If I pass arguments of the form --flag=value it crashes without any info (not even with debugger attached).
If I pass --flag value it works.

The flag in question is unrelated to magnum (it's used for something else).


  • Visual Studio 2017 (15.9.4)
  • Debug
  • x86
  • Argument: --flag=value = Fail
  • Argument: --flag value = Success
    (Only tested with above config so far)
struct app : public Magnum::Platform::Application
    explicit app(const Arguments& arguments) :
    { }

    virtual void drawEvent() override

int main(int argc, char * argv[])
    //std::vector<std::string> args(argv + 1, argv + argc);
    app myApp(Magnum::Platform::Sdl2Application::Arguments(argc, argv));
    return 0;

myapp-d.exe: Native' has exited with code -1 (0xffffffff).

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mosra commented Jan 9, 2019

Thanks for the report!

This is a ... unfortunate combination of corner cases :) The Utility::Arguments class:

  • supports only --flag value, not --flag=value at the moment (it was originally done to make the implementation slightly simpler, but could be easily updated)
  • for magnum *Application classes, all arguments that do not start with --magnum- are ignored (to allow users having their own Utility::Arguments for command-line options and not getting errors about unknown arguments)
  • but only if the argument name is valid (only alphanumeric characters and a -)

So if you would pass e.g. --? there, it would fail too, the same way. I guess the way to fix this is by reverting the order of checks, so first ignore everything non-prefixed and only then check for name validity. Will do that.

What is interesting is that it crashes without any info for you. In my case I get this:

$ magnum-triangle --flag=value
Invalid command-line argument --flag=value
  magnum-triangle [--magnum-help] 
    [--magnum-dpi-scaling default|virtual|physical|<d>|"<h> <v>"] 
    [--magnum-disable-workarounds LIST] [--magnum-disable-extensions LIST] 
    [--magnum-log default|quiet|verbose] ...

@mosra mosra added this to the 2019.01 milestone Jan 9, 2019
@mosra mosra added this to TODO in Project management via automation Jan 9, 2019
@mosra mosra self-assigned this Jan 9, 2019
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helmesjo commented Jan 9, 2019

Oh, sorry, you are right! I see now that I do get that output (I was just stepping the code and didn't pay attention to the console, only the output in VS 😇 ). But, while debugging it is a dead-hard crash (doesn't even brake).

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mosra commented Jan 10, 2019

Fixed in mosra/corrade@c11652e, it should not complain anymore but instead ignore the argument completely (as it should be). (It'll be complaining again when you pass e.g. --magnum-blah to it, which is an unknown argument.) I'll be tracking the support for --flag=value (instead of --flag value) separately, so closing this one as resolved.

The Arguments class is calling std::exit() with a non-zero code when it encounters some error in the command-line arguments. It's not a crash, but also not a successful exit, so it can't just return 0. Not sure if the VS debugger can attach to that :)

@mosra mosra closed this as completed Jan 10, 2019
Project management automation moved this from TODO to Done Jan 10, 2019
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