stack unwindings

每次函数调用发生的时候，都会执行保护现场寄存器、参数压栈、为被调用的函数创建堆栈这几个对堆栈的操作，它们都使堆栈增长。每次函数返回则是恢复现场，使堆栈减小。我们把函数返回过程中恢复现场的过程称为unwinding stack.


The exception-handling index tables generated by the compiler are given the section name .ARM.exidx.  For more information, please see the .  At link time these tables must be placed in the same execution region and be contiguous.  If a user explicitly places these sections non-contiguously using specific selector patterns in their scatter-loading description file, then this error message is likely to occur.


The runtime environment must ensure a stack unwind cannot proceed beyond the valid stack region, possibly by marking the caller of main() as EXIDX_CANTUNWIND.

.ARM.exidx names a section that contains index entries for section unwinding.

#ifdef __LEAVE_EQUALS_THROW__
  asm(".word .ARM.exidx$$Base");   /* index table base */
  asm(".word .ARM.exidx$$Limit");  /* index table limit */
#endif