[clang] Give better message for unsupported no_sanitize on globals

Previously if you specified no_sanitize("known_sanitizer") on a global you
would yield a misleading error "'no_sanitize' attribute only applies to
functions and methods", but no_sanitize("unknown") would simply be a warning,
"unknown sanitizer 'unknown' ignored". This changes the former to a warning
"'no_sanitize' attribute argument not supported for globals: known_sanitizer".

Differential Revision: https://reviews.llvm.org/D133117

clang/docs/ReleaseNotes.rst

@@ -127,6 +127,9 @@ Improvements to Clang's diagnostics
   supports both c and c++ language.
 - When diagnosing multi-level pack expansions of mismatched lengths, Clang will
   now, in most cases, be able to point to the relevant outer parameter.
+- no_sanitize("...") on a global variable for known but not relevant sanitizers
+  is now just a warning. It now says that this will be ignored instead of
+  incorrectly saying no_sanitize only applies to functions and methods.
 
 Non-comprehensive list of changes in this release
 -------------------------------------------------

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -4052,6 +4052,9 @@ def warn_transparent_union_attribute_zero_fields : Warning<
 def warn_attribute_type_not_supported : Warning<
   "%0 attribute argument not supported: %1">,
   InGroup<IgnoredAttributes>;
+def warn_attribute_type_not_supported_global : Warning<
+  "%0 attribute argument '%1' not supported on a global variable">,
+  InGroup<IgnoredAttributes>;
 def warn_attribute_unknown_visibility : Warning<"unknown visibility %0">,
   InGroup<IgnoredAttributes>;
 def warn_attribute_protected_visibility :

clang/lib/Sema/SemaDeclAttr.cpp

@@ -7877,8 +7877,8 @@ static void handleNoSanitizeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
         SanitizerName != "coverage")
       S.Diag(LiteralLoc, diag::warn_unknown_sanitizer_ignored) << SanitizerName;
     else if (isGlobalVar(D) && !isSanitizerAttributeAllowedOnGlobals(SanitizerName))
-      S.Diag(D->getLocation(), diag::err_attribute_wrong_decl_type)
+      S.Diag(D->getLocation(), diag::warn_attribute_type_not_supported_global)
-          << AL << ExpectedFunctionOrMethod;
+          << AL << SanitizerName;
     Sanitizers.push_back(SanitizerName);
   }
 

clang/test/SemaCXX/attr-no-sanitize.cpp

@@ -6,6 +6,9 @@ int f1() __attribute__((no_sanitize)); // expected-error{{'no_sanitize' attribut
 
 int f2() __attribute__((no_sanitize(1))); // expected-error{{'no_sanitize' attribute requires a string}}
 
+__attribute__((no_sanitize("all"))) int global; // expected-warning{{'no_sanitize' attribute argument 'all' not supported on a global variable}}
+__attribute__((no_sanitize("unknown"))) int global2; // expected-warning{{unknown sanitizer 'unknown' ignored}}
+
 // DUMP-LABEL: FunctionDecl {{.*}} f3
 // DUMP: NoSanitizeAttr {{.*}} address
 // PRINT: int f3() __attribute__((no_sanitize("address")))