Error: quartus: xcb_xlib.c:82:xcb_xlib_unlock: Assertion c->xlib.lock failed. - Error: quartus: xcb_xlib.c:82:xcb_xlib_unlock: Assertion c->xlib.lock failed. Description If your Linux operating system uses the X protocol C-language Binding (XCB) library (libxcb), the Quartus II software might fail to start with an error similar to the following: quartus: xcb_xlib.c:82:xcb_xlib_unlock: Assertion "c->xlib.lock" failed. Resolution Upgrade you Linux distribution to the latest version or, if your Linux distribution uses libxcb version 1.1, run export LIBXCB_ALLOW_SLOPPY_LOCK=1 before running the Quartus II software version 11.0. Custom Fields values: ['novalue'] Troubleshooting novalue True ['novalue'] ['FPGA Dev Tools Quartus II Software'] novalue 11.0 ['Programmable Logic Devices'] ['novalue'] ['novalue'] ['novalue']