Re: [PATCH] Remove zero PC check from blockframe.c:inside_main_func()

[Andrew Cagney <cagney at gnu dot org>]

> It really makes no sense to check for a zero PC here.  This function
> is only colled from frame.c:get_prev_frame(), and there we already
> deal with PC being zero.
>
> The whole concept of using a zero PC as a marker for the end of the
> frame chain is somewhat flawed.  It prevents us from providing a
> meaningful backtrace when the program has called a null function
> pointer; see backtrace/1476.  At the very least we will have to treat
> a zero PC in the innermost differently.  Classifying the a zero PC as
> being inside the "main" function doesn't help.  Therefore this patch
> removes the first obstackle in fixing that PR.
>
> Objections.  Otherwise I'll commit this within a few days.

FYI, this was made active with:

        * blockframe.c: Include "gdbcmd.h" and "command.h".
        (backtrace_below_main): New variable.
        (file_frame_chain_valid, func_frame_chain_valid)
        (nonnull_frame_chain_valid, generic_file_frame_chain_valid)
        (generic_func_frame_chain_valid): Remove functions.
        (frame_chain_valid, do_flush_frames_sfunc): New functions.
        (_initialize_blockframe): New function.
        * Makefile.in (blockframe.o): Update dependencies.
        * frame.c (frame_saved_regs_id_unwind, get_prev_frame): Remove 
FIXME
        comment.  Call frame_chain_valid ().
        * frame.h: Remove old prototypes.  Add prototype for
        frame_chain_valid and update comments to match.
        * gdbarch.sh: Change FRAME_CHAIN_VALID into a predicated function.
        Remove old comment.
        * gdbarch.h: Regenerated.
        * gdbarch.c: Regenerated.

rather than the new frame code.

I looked at the new frame code and apart from the wild-card logic, there 
weren't any obvious PC==0 tests.

Andrew