How can I give to a user the possibility to send a crash report from inside my application ?
Crash report
You can get some crash reports directly from Xcode. Open the "Organizer", select your archive from the list and select the Crashes tab. Though this only gives you a small sample of the crash reports your user might be experiencing. There are 3rd party frameworks that do this much better, and let users fill in an email address or notes about the crash. I use HockeyApp, and it works well for me. You can search for others like this.