check_timing的warning，请帮忙分析。

sta时，check_timing出很多warning，命令返回0，如何逐个debug?我贴出log信息：
pt_shell> check_timing
Information: Checking 'no_driving_cell'.
Information: Checking 'unconstrained_endpoints'.
Warning: There are 25 endpoints which are not constrained for maximum delay.
Information: Checking 'unexpandable_clocks'.
Warning: There is 1 clock set for which periods were not expandable.
Information: Checking 'latch_fanout'.
Information: Checking 'no_clock'.
Warning: There are 7 register clock pins with no clock.
Information: Checking 'partial_input_delay'.
Warning: There are 34 ports with partially defined input delays.
Information: Checking 'generic'.
Information: Checking 'loops'.
Warning: There are 57 timing loops in the design.
Information: Checking 'generated_clocks'.
Information: Checking 'pulse_clock_non_pulse_clock_merge'.
Information: Checking 'pll_configuration'.
0
pt_shell>

这一条条说得够清楚了，加-verbose选项看详细的list，照着改就是了

据经验来，基本上就是看看，很少有实质上的作用

那个warning 也会导致返回值是0吗