[PATCH] Fix out-of-bounds write in RTL function reader (PR bootstrap/79952)

[David Malcolm]

On Fri, 2017-03-10 at 00:36 +0100, Bernd Schmidt wrote:
> On 03/09/2017 08:28 PM, David Malcolm wrote:
> > The root cause is an out-of-bounds memory write in the RTL dump
> > reader when handling SYMBOL_REFs with SYMBOL_FLAG_HAS_BLOCK_INFO
> > set.
> > 
> > Such SYMBOL_REFs are normally created by
> > varasm.c:create_block_symbol,
> > which has:
> 
> Hmm, I don't actually recall seeing this stuff. It's for section
> anchors 
> apparently.
> 
> > OK for trunk in stage 4?
> > 
> > gcc/ChangeLog:
> > 	PR bootstrap/79952
> > 	* read-rtl-function.c (function_reader::read_rtx_operand):
> > Update
> > 	x with result of extra_parsing_for_operand_code_0.
> > 	(function_reader::extra_parsing_for_operand_code_0): Convert
> > 	return type from void to rtx, returning x.  When reading
> > 	SYMBOL_REF with SYMBOL_FLAG_HAS_BLOCK_INFO, reallocate x to the
> > 	larger size containing struct block_symbol.
> 
> Looks OK for now, but longer term I think we should make it possible
> to 
> reconstruct this data.

Thanks; fix committed to trunk as r246044.

I'm also not very familiar with this part of RTL.

print-rtl.c:rtx_writer::print_rtx_operand_code_0 has some special
-casing for SYMBOL_REF, but if I'm reading things right we don't yet
dump SYMBOL_REF_BLOCK and SYMBOL_REF_BLOCK_OFFSET, so we'd need to dump
these somehow.