[PATCH] c++: Ignore __sanitizer_ptr_{sub,cmp} builtin calls during constant expression evaluation [PR97145]

[PATCH] c++: Ignore __sanitizer_ptr_{sub,cmp} builtin calls during constant expression evaluation [PR97145]

[Jakub Jelinek]

Hi!

These two builtin calls are added already during parsing before pointer
subtractions or comparisons, normally they perform runtime verification
of whether the pointers point to the same object or different objects,
but during constant expressione valuation we don't really need those
builtins for anything.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2020-09-22  Jakub Jelinek  <jakub@redhat.com>

	PR c++/97145
	* constexpr.c (cxx_eval_builtin_function_call): Return void_node for
	calls to __sanitize_ptr_{sub,cmp} builtins.

	* g++.dg/asan/pr97145.C: New test.

--- gcc/cp/constexpr.c.jj	2020-09-07 16:58:53.342195330 +0200
+++ gcc/cp/constexpr.c	2020-09-21 23:50:39.909211245 +0200
@@ -1355,6 +1355,12 @@ cxx_eval_builtin_function_call (const co
       case BUILT_IN_STRSTR:
 	strops = 2;
 	strret = 1;
+	break;
+      case BUILT_IN_ASAN_POINTER_COMPARE:
+      case BUILT_IN_ASAN_POINTER_SUBTRACT:
+	/* These builtins shall be ignored during constant expression
+	   evaluation.  */
+	return void_node;
       default:
 	break;
       }
--- gcc/testsuite/g++.dg/asan/pr97145.C.jj	2020-09-21 17:37:50.408562876 +0200
+++ gcc/testsuite/g++.dg/asan/pr97145.C	2020-09-21 17:38:26.961031023 +0200
@@ -0,0 +1,7 @@
+// PR c++/97145
+// { dg-do compile { target c++11 } }
+// { dg-options "-fsanitize=address,pointer-subtract,pointer-compare" }
+
+constexpr char *a = nullptr;
+constexpr auto b = a - a;
+constexpr auto c = a < a;

	Jakub

Re: [PATCH] c++: Ignore __sanitizer_ptr_{sub,cmp} builtin calls during constant expression evaluation [PR97145]

[Jason Merrill]

On 9/22/20 3:48 AM, Jakub Jelinek wrote:
> Hi!
> 
> These two builtin calls are added already during parsing before pointer
> subtractions or comparisons, normally they perform runtime verification
> of whether the pointers point to the same object or different objects,
> but during constant expressione valuation we don't really need those
> builtins for anything.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK.

> 2020-09-22  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR c++/97145
> 	* constexpr.c (cxx_eval_builtin_function_call): Return void_node for
> 	calls to __sanitize_ptr_{sub,cmp} builtins.
> 
> 	* g++.dg/asan/pr97145.C: New test.
> 
> --- gcc/cp/constexpr.c.jj	2020-09-07 16:58:53.342195330 +0200
> +++ gcc/cp/constexpr.c	2020-09-21 23:50:39.909211245 +0200
> @@ -1355,6 +1355,12 @@ cxx_eval_builtin_function_call (const co
>         case BUILT_IN_STRSTR:
>   	strops = 2;
>   	strret = 1;
> +	break;
> +      case BUILT_IN_ASAN_POINTER_COMPARE:
> +      case BUILT_IN_ASAN_POINTER_SUBTRACT:
> +	/* These builtins shall be ignored during constant expression
> +	   evaluation.  */
> +	return void_node;
>         default:
>   	break;
>         }
> --- gcc/testsuite/g++.dg/asan/pr97145.C.jj	2020-09-21 17:37:50.408562876 +0200
> +++ gcc/testsuite/g++.dg/asan/pr97145.C	2020-09-21 17:38:26.961031023 +0200
> @@ -0,0 +1,7 @@
> +// PR c++/97145
> +// { dg-do compile { target c++11 } }
> +// { dg-options "-fsanitize=address,pointer-subtract,pointer-compare" }
> +
> +constexpr char *a = nullptr;
> +constexpr auto b = a - a;
> +constexpr auto c = a < a;
> 
> 	Jakub
>