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polybar / xpp

xpp - A C++11 RAII wrapper for XCB
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xpp::connection segfaults when there is a problem connecting to X #32

Open zybreak opened 2 years ago

zybreak commented 2 years ago

I have identified 2 possible scenarios so far. #1 is when we create a connection and specify extensions, then the segfault seems to happen in the extension.

dispatcher(const xpp::shape::extension & extension)
      : dispatcher(extension->first_error)  <--- this line
    {}

If no extensions are specified, the segfault happens because the connection objects tries to fetch the root screen, without checking for a successful connection first.

The second segfault is pretty simple to fix, but the first one requires more c++ skills than I currently have :)

zybreak commented 2 years ago

To reproduce, instansiate a connection like so and set the DISPLAY environment variable to point at some non-running X address. expected result is the graceful shutdown with a error message, instead it segfaults

    xpp::connection<xpp::xkb::extension, xpp::shape::extension, xpp::big_requests::extension, xpp::randr::extension> a;
    if (a.connection_has_error())
        errx(EXIT_FAILURE, "Cannot open display");
patrick96 commented 2 years ago

Thanks for letting me know.

I don't see an immediate fix for the first segfault, I'm not even sure what exactly causes it.

We're not really maintaining this library for general use, we don't have the capacity for that. We only keep it because we need it for polybar.