The launcher will usually crash upon clicking play and launching Minecraft. Sometimes Minecraft will open regardless, and other times a second error message will appear instead.

I've tried the setting that allows the log to open, but that only appears when Minecraft opens successfully, in which case there is nothing to report. Hence, there is nothing to attach.

Possibly related: Launcher sometimes fails to open at all; this usually occurs after successfully opening and closing Minecraft.

To recreate, I just open the launcher, and click 'play.'