C PATCH to fix ICE with old-style parameter declarations with initializers (PR sanitizer/79757)

[Jeff Law]

On 03/06/2017 02:44 PM, Marek Polacek wrote:
> This is an ICE with -fsanitize=undefined on invalid code involving old-style
> parameter declarations and nested functions.  Ugh.
>
> Old-style parameter declarations cannot have initializers, and start_decl
> errors when it sees that something's trying to initialize a PARM_DECL, but
> nonetheless, we still attempt to parse the initializer, eventually arriving in
> build_binary_op, which means we will instrument the bogus initializer.
>
> This causes a crash in ubsan_encode_value -> create_tmp_var -> declare_vars: it
> thinks it's processing a nested function, but the body of the function is null,
> leading to the crash.
>
> I suppose the best fix is to avoid instrumenting such bogus initializers.  In
> c_parser_declaration_or_fndef it's easy to determine if we're initializing a
> PARM_DECL -- just check DECL's code, but with __auto_type that's not possible,
> because start_decl is called *after* parsing the initializer.  So instead of
> DECL's code I'm checking nested && !empty_ok.
>
> But we still want to instrument variables with initializers in nested
> functions, so I've added two run-time tests for that.
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
>
> 2017-03-06  Marek Polacek  <polacek@redhat.com>
>
> 	PR sanitizer/79757
> 	* c-parser.c (c_parser_declaration_or_fndef): Don't sanitize old-style
> 	parameter declarations with initializers.
>
> 	* gcc.dg/ubsan/pr79757-1.c: New test.
> 	* gcc.dg/ubsan/pr79757-2.c: New test.
> 	* gcc.dg/ubsan/pr79757-3.c: New test.
> 	* gcc.dg/ubsan/pr79757-4.c: New test.
> 	* gcc.dg/ubsan/pr79757-5.c: New test.
This isn't marked as a regression, but it clearly is a regression given 
we didn't ICE prior to r205714.

OK for the trunk.

Thanks for adding tests that verify we are instrumenting initializers in 
nested functions.

jeff