[clang] Move warning about memset/memcpy to NonTriviallyCopyable types to its own flag

Namely -Wnontrivial-memcall, implied by -Wnontricial-memaccess

This is a followup to llvm#111434

Author: serge-sans-paille

clang/docs/ReleaseNotes.rst

@@ -404,7 +404,7 @@ Modified Compiler Flags
   to utilize these vector libraries. The behavior for all other vector function
   libraries remains unchanged.
 
-- The ``-Wnontrivial-memaccess`` warning has been updated to also warn about
+- The ``-Wnontrivial-memcall`` warning has been updated to also warn about
   passing non-trivially-copyable destrination parameter to ``memcpy``,
   ``memset`` and similar functions for which it is a documented undefined
   behavior.

clang/include/clang/Basic/DiagnosticGroups.td

@@ -683,11 +683,13 @@ def SizeofArrayDecay : DiagGroup<"sizeof-array-decay">;
 def SizeofPointerMemaccess : DiagGroup<"sizeof-pointer-memaccess">;
 def MemsetTransposedArgs : DiagGroup<"memset-transposed-args">;
 def DynamicClassMemaccess : DiagGroup<"dynamic-class-memaccess">;
-def NonTrivialMemaccess : DiagGroup<"nontrivial-memaccess">;
+def NonTrivialMemcall : DiagGroup<"nontrivial-memcall">;
+def NonTrivialMemaccess : DiagGroup<"nontrivial-memaccess", [NonTrivialMemcall]>;
 def SuspiciousBzero : DiagGroup<"suspicious-bzero">;
 def SuspiciousMemaccess : DiagGroup<"suspicious-memaccess",
   [SizeofPointerMemaccess, DynamicClassMemaccess,
-   NonTrivialMemaccess, MemsetTransposedArgs, SuspiciousBzero]>;
+   NonTrivialMemaccess, NonTrivialMemcall, MemsetTransposedArgs,
+   SuspiciousBzero]>;
 def StaticInInline : DiagGroup<"static-in-inline">;
 def StaticLocalInInline : DiagGroup<"static-local-in-inline">;
 def GNUStaticFloatInit : DiagGroup<"gnu-static-float-init">;

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -798,7 +798,7 @@ def warn_cstruct_memaccess : Warning<
 def warn_cxxstruct_memaccess : Warning<
   "first argument in call to "
   "%0 is a pointer to non-trivially copyable type %1">,
-  InGroup<NonTrivialMemaccess>;
+  InGroup<NonTrivialMemcall>;
 def note_nontrivial_field : Note<
   "field is non-trivial to %select{copy|default-initialize}0">;
 def err_non_trivial_c_union_in_invalid_context : Error<

clang/test/SemaCXX/warn-memcall.cpp

@@ -0,0 +1,27 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -Wnontrivial-memcall %s
+
+extern "C" void *memcpy(void *s1, const void *s2, unsigned n);
+
+class TriviallyCopyable {};
+class NonTriviallyCopyable { NonTriviallyCopyable(const NonTriviallyCopyable&);};
+struct Incomplete;
+
+void test_memcpy(TriviallyCopyable* tc0, TriviallyCopyable* tc1,
+                 NonTriviallyCopyable *ntc0, NonTriviallyCopyable *ntc1,
+                 Incomplete *i0, Incomplete *i1) {
+  // OK
+  memcpy(tc0, tc1, sizeof(*tc0));
+
+  // OK
+  memcpy(i0, i1, 10);
+
+  // expected-warning@+2{{first argument in call to 'memcpy' is a pointer to non-trivially copyable type 'NonTriviallyCopyable'}}
+  // expected-note@+1{{explicitly cast the pointer to silence this warning}}
+  memcpy(ntc0, ntc1, sizeof(*ntc0));
+
+  // ~ OK
+  memcpy((void*)ntc0, ntc1, sizeof(*ntc0));
+
+  // OK
+  memcpy((void*)ntc0, (void*)ntc1, sizeof(*ntc0));
+}