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

[helmesjo]

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).

Reproduce:

• 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) :
        Magnum::Platform::Application(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;
}

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

[mosra]

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
Usage:
  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] ...

[helmesjo]

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).

[mosra]

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 :)