Re: [Patch] MIPS: Fix unwinding through signal frames for n32 and n64 ABIs.

[David Daney <ddaney at avtrex dot com>]

David Daney wrote:

> +/* The DWARF 2 CFA column which tracks the return address from a
> +   signal handler context.  This means that to maintain backwards
> +   compatibility, no hard register can be assigned this column if it
> +   would need to be handled by the DWARF unwinder.  */
> +#define DWARF_ALT_FRAME_RETURN_COLUMN 66

Thinking about it a bit more, I think the comment is incorrect.

In the future we could put a hard register in column 66, we would just have to move DWARF_ALT_FRAME_RETURN_COLUMN somewhere else.  There is no promise that code compiled by future versions of GCC will work with older versions of libgcc_s.so.  In fact there are symbol versions in libgcc_s.so that are there to explicitly prevent it from happening.

If the patch is approved, I will remove the second sentence.

David Daney