[PATCH] Verify __builtin_unreachable and __builtin_trap are not called with arguments

[Richard Biener]

On April 22, 2016 7:04:31 PM GMT+02:00, Martin Jambor <mjambor@suse.cz> wrote:
>Hi,
>
>this patch adds verification that __builtin_unreachable and
>__builtin_trap are not called with arguments.  The problem with calls
>to them with arguments is that functions like gimple_call_builtin_p
>return false on them, because they return true only when
>gimple_builtin_call_types_compatible_p does.  One manifestation of
>that was PR 61591 where undefined behavior sanitizer did not replace
>such calls with its thing as it should, but there might be others.
>
>I have included __builtin_trap in the verification because they often
>seem to be handled together but can either remove it or add more
>builtins if people think it better.  I concede it is a bit arbitrary.
>
>Honza said he has seen __builtin_unreachable calls with parameters in
>LTO builds of Firefox, so it seems this might actually trigger, but I
>also think we do not want such calls in the IL.
>
>I have bootstrapped and tested this on x86_64-linux (with all
>languages and Ada) and have also run a C, C++ and Fortran LTO
>bootstrap with the patch on the same architecture.  OK for trunk?

Shouldn't we simply error in the FEs for this given the builtins essentially have a prototype?  That is, error for non-matching args for the __built-in_ variant of _all_ builtins (treat them as prototyped)?

Richard.

>Thanks,
>
>Martin
>
>
>2016-04-20  Martin Jambor  <mjambor@suse.cz>
>
>	* tree-cfg.c (verify_gimple_call): Check that calls to
>	__builtin_unreachable or __builtin_trap do not have actual arguments.
>---
> gcc/tree-cfg.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
>diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
>index 04e46fd..3385164 100644
>--- a/gcc/tree-cfg.c
>+++ b/gcc/tree-cfg.c
>@@ -3414,6 +3414,26 @@ verify_gimple_call (gcall *stmt)
>       return true;
>     }
> 
>+  if (fndecl && DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL)
>+    {
>+      switch (DECL_FUNCTION_CODE (fndecl))
>+	{
>+	case BUILT_IN_UNREACHABLE:
>+	case BUILT_IN_TRAP:
>+	  if (gimple_call_num_args (stmt) > 0)
>+	    {
>+	      /* Built-in unreachable with parameters might not be caught by
>+		 undefined behavior santizer. */
>+	      error ("__builtin_unreachable or __builtin_trap call with "
>+		     "arguments");
>+	      return true;
>+	    }
>+	  break;
>+	default:
>+	  break;
>+	}
>+    }
>+
>   /* ???  The C frontend passes unpromoted arguments in case it
>      didn't see a function declaration before the call.  So for now
>      leave the call arguments mostly unverified.  Once we gimplify