when i start minecraft through the launcher,it crashes and sends a crash report.

Put the summary of the bug you're having here
i crash when i start minecraft
What I expected to happen was...:
the game would start,and i would play

What actually happened was...:
the launcher came back up and sent me a crash report

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...