Terminated due to signal X

当Xcode闪退提示“Message from debugger: Terminated due to signal 9”时，意思是程序收到信号9主动退出应用。收到信号9的原因有：内存不足，或CPU使用率过高时，程序主动终止了运行。

signal 是Linux/Unix 中的 signal 。来着：https://www.lifewire.com/signal-linux-command-4094016

Term: Default action is to terminate the process.//默认终止进程
Ign: Default action is to ignore the signal.//默认忽略信号
Core: Default action is to terminate the process and dump core.//默认终止进程并且内核转储
Stop: Default action is to stop the process.//默认停止进程

Signal	Value	Action	Comment
			or death of controlling process
SIGINT	2	Term	Interrupt from
SIGQUIT	3	Core	Quit from
SIGILL	4	Core	illegal
SIGABRT	6	Core	Abort signal
SIGFPE	8	Core	Floating point
SIGKILL	9	Term	Kill signal
SIGSEGV	11	Core	Invalid memory
SIGPIPE	13	Term	Broken pipe: write to pipe with no readers
SIGALRM	14	Term	Timer signal
SIGTERM	15	Term	Termination signal
SIGUSR	130,10,16	Term	User-defined signal 1
SIGUSR2	31,12,17	Term	User-defined signal 2
SIGCHLD	20,17,18	Ign	Child stopped or terminated
SIGCONT	19,18,25		Continue if stopped
SIGSTOP	17,19,23	Stop	Stop process
SIGTSTP	18,20,24	Stop	Stop typed at tty
SIGTTIN	21,21,26	Stop	tty input for background process
SIGTTOU	22,22,27	Stop	tty output for background process