Address review feedback.

- tweaks to header/doc comments
- add test for wide string literal

Author: ahmedbougacha

clang/docs/PointerAuthentication.rst

@@ -335,13 +335,15 @@ result has type ``ptrauth_extra_data_t``.
 
   ptrauth_string_discriminator(string)
 
-Produce a discriminator value for the given string.  ``string`` must be
-a string literal of ``char`` character type.  The result has type
-``ptrauth_extra_data_t``.
+Compute a constant discriminator from the given string.
 
-The result is always a constant expression.  The result value is never zero and
-always within range for both the ``__ptrauth`` qualifier and
-``ptrauth_blend_discriminator``.
+``string`` must be a string literal of ``char`` character type.  The result has
+type ``ptrauth_extra_data_t``.
+
+The result value is never zero and always within range for both the
+``__ptrauth`` qualifier and ``ptrauth_blend_discriminator``.
+
+This can be used in constant expressions.
 
 ``ptrauth_strip``
 ^^^^^^^^^^^^^^^^^

clang/lib/Headers/ptrauth.h

@@ -127,12 +127,14 @@ typedef __UINTPTR_TYPE__ ptrauth_generic_signature_t;
 
 /* Compute a constant discriminator from the given string.
 
-   The result can be used as the second argument to
-   ptrauth_blend_discriminator or the third argument to the
-   __ptrauth qualifier.  It has type size_t.
+   The argument must be a string literal of char character type.  The result
+   has type ptrauth_extra_data_t.
 
-   The argument must be a string literal.
-   A call to this function is an integer constant expression. */
+   The result value is never zero and always within range for both the
+   __ptrauth qualifier and ptrauth_blend_discriminator.
+
+   This can be used in constant expressions.
+*/
 #define ptrauth_string_discriminator(__string)                                 \
   __builtin_ptrauth_string_discriminator(__string)
 

clang/test/Sema/ptrauth.c

@@ -53,6 +53,7 @@ void test_string_discriminator(const char *str) {
   (void) __builtin_ptrauth_string_discriminator("test string"); // no warning
 
   __builtin_ptrauth_string_discriminator(str); // expected-error {{argument must be a string literal}}
+  __builtin_ptrauth_string_discriminator(L"wide test"); // expected-error {{argument must be a string literal}} expected-warning {{incompatible pointer types passing 'int[10]' to parameter of type 'const char *'}}
 
   void *mismatch = __builtin_ptrauth_string_discriminator("test string"); // expected-error {{incompatible integer to pointer conversion initializing 'void *' with an expression of type 'unsigned long'}}
 }