PR debug/17406: ICE dwarf2out_frame_debug_expr on MinGW

[James E Wilson]

Aaron W. LaFramboise wrote:
> Could somebody give me some quick information about the prognosis of
> this bug?

We rely on volunteer labor to fix bugs, so there is no way for us to 
predict when it might be fixed.  Also, the tree is rather unsetttled at 
the moment, as there are multiple bugs causing bootstrap problems on 
multiple targets.

> In addition, as who is still very much a GCC beginner, do I have any
> chance at all of being able to fix this myself?

This isn't clear from the info in the PR.  If you want to try taking a 
look, it wouldn't hurt.

You can pretty print rtl by using some gdb macros, though should be 
automatically loaded from the .gdbinit file.  So you can do
(gdb) print dest
(gdb) pr
to see what the RTL for dest is.  You probably want expr, dest, and src 
here.

 From the line number, it looks like it hit the gcc_unreachable line at 
the end, but you seem to have a MEM, and there is a MEM case, so it 
isn't clear why this happened.

Try putting a breakpoint in the dwarf2out_frame_debug_expr function and 
step through it to see what is happening.

You can generate a testcase by using --save-temps which will give you a 
.i file to use as input to cc1.

If the function is too hard to debug, you might try rebuilding 
dwarf2out.c with -O1 or -O0.  The default -O2 sometimes makes debugging 
too difficult to be useful.
-- 
Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com