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Re: Request to merge Undefined Behavior Sanitizer in (take 2)


Ping.

On Wed, Aug 07, 2013 at 06:12:58PM +0200, Marek Polacek wrote:
> On Wed, Aug 07, 2013 at 10:24:59AM -0400, Jason Merrill wrote:
> > On 08/07/2013 06:06 AM, Marek Polacek wrote:
> > >I might've misunderstood what you mean.  If we drop the hunk above,
> > >then we'll call
> > >     error ("%q+E is not a constant expression", t);
> > >so, we'll print "is not a constant expression" no matter what
> > 
> > Yes, that's fine; 1/0 is not a constant expression, because it has
> > undefined behavior.
> 
> Indeed.
> 
> > Print something more meaningful to the user.
> 
> Something along these lines?  (Not including CL/testcase yet on purpose.)
> In beforementioned situation it'd print:
> 
> w.C:7:22: error: â<ubsan routine call>â is not a constant expression
>        case 0 * (1 / 0):
>                       ^
> I'm not entirely happy about it, on the other hand, this situation
> should be very rare...
> 
> diff --git a/gcc/cp/error.c b/gcc/cp/error.c
> index 440169a..db50b5f 100644
> --- a/gcc/cp/error.c
> +++ b/gcc/cp/error.c
> @@ -32,6 +32,7 @@ along with GCC; see the file COPYING3.  If not see
>  #include "tree-pretty-print.h"
>  #include "pointer-set.h"
>  #include "c-family/c-objc.h"
> +#include "ubsan.h"
>  
>  #define pp_separate_with_comma(PP) pp_cxx_separate_with (PP, ',')
>  #define pp_separate_with_semicolon(PP) pp_cxx_separate_with (PP, ';')
> @@ -1972,6 +1973,12 @@ dump_expr (tree t, int flags)
>  	      }
>  	    skipfirst = true;
>  	  }
> +	if (flag_sanitize & SANITIZE_UNDEFINED
> +	    && is_ubsan_builtin_p (fn))
> +	  {
> +	    pp_string (cxx_pp, M_("<ubsan routine call>"));
> +	    break;
> +	  }
>  	dump_expr (fn, flags | TFF_EXPR_IN_PARENS);
>  	dump_call_expr_args (t, flags, skipfirst);
>        }
> diff --git a/gcc/ubsan.c b/gcc/ubsan.c
> index 8135cc9..565758d 100644
> --- a/gcc/ubsan.c
> +++ b/gcc/ubsan.c
> @@ -456,3 +456,13 @@ ubsan_instrument_unreachable (location_t loc)
>    tree t = builtin_decl_explicit (BUILT_IN_UBSAN_HANDLE_BUILTIN_UNREACHABLE);
>    return build_call_expr_loc (loc, t, 1, build_fold_addr_expr_loc (loc, data));
>  }
> +
> +/* Return true if T is a call to a libubsan routine.  */
> +
> +bool
> +is_ubsan_builtin_p (tree t)
> +{
> +  gcc_checking_assert (TREE_CODE (t) == FUNCTION_DECL);
> +  return strncmp (IDENTIFIER_POINTER (DECL_NAME (t)),
> +		  "__builtin___ubsan_", 18) == 0;
> +}
> diff --git a/gcc/ubsan.h b/gcc/ubsan.h
> index abf4f5d..3553a6c 100644
> --- a/gcc/ubsan.h
> +++ b/gcc/ubsan.h
> @@ -25,6 +25,7 @@ extern tree ubsan_instrument_unreachable (location_t);
>  extern tree ubsan_create_data (const char *, location_t, ...);
>  extern tree ubsan_type_descriptor (tree);
>  extern tree ubsan_encode_value (tree);
> +extern bool is_ubsan_builtin_p (tree);
>  
>  #endif  /* GCC_UBSAN_H  */

	Marek


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