Why does the TimeQuest timing analyzer ignore set_clock_groups constraints?

Due to an error in the Quartus® II software version 11.1 SP2 and earlier, the TimeQuest timing analyzer may ignoreset_clock_groups constraints if they are written with backslashes (""):

set_clock_groups -asynchronous -group {clk_A} -group {clk_B} -group {clk_C}

This may result in timing paths reported even though the paths have been cut using the set_clock_groupsconstraint.

To work around this problem, delete the "\" and create the constraint in one line in your Synopsys Design Constraints file (.sdc). For example, modify the previous constraint as follows:

set_clock_groups -asynchronous -group {clk_A} -group {clk_B} -group {clk_C}

This error is scheduled to be fixed in a future release of the Quartus II software.