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C++ PATCH for c++/88136, -Wdeprecated-copy too noisy


-Wdeprecated-copy does find some real bugs, but it also complains
about a lot of reasonable code for which the implicitly declared copy
ctor/op= are fine oven though the class has a user-defined destructor:
this situation is only problematic if the destructor releases
resources held in one of the non-static data members.

So, this patch reins it in somewhat: first by moving from -Wall to
-Wextra, and then also only complaining if the other copy op is
user-declared.  The old behavior can be explicitly requested with
-Wdeprecated-copy-dtor.

Tested x86_64-pc-linux-gnu, applying to trunk.
commit c37377416dcbf21c6b9f6c7b83fd8f9587b0a517
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Nov 21 18:04:02 2018 -0500

            PR c++/88136 - -Wdeprecated-copy false positives
    
    Deprecating the copy operations because the class has a user-provided
    destructor turns out to have too many false positives; this patch adjusts
    -Wdeprecated-copy to only deprecate if the other copy operation is
    user-provided.  To get the earlier behavior, people can explicitly request
    it with -Wdeprecated-copy-dtor.
    
    gcc/c-family/
            * c.opt (Wdeprecated-copy-dtor): New.
            (Wdeprecated-copy): Move to -Wextra.
    gcc/cp/
            * class.c (classtype_has_depr_implicit_copy): Rename from
            classtype_has_user_copy_or_dtor.
            * method.c (lazily_declare_fn): Adjust.
            * decl2.c (cp_warn_deprecated_use): Refer to -Wdeprecated-copy-dtor
            if deprecation is due to a destructor.

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 3b6912ea1cc..98c1a748329 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -228,7 +228,8 @@ in the following sections.
 -fvisibility-ms-compat @gol
 -fext-numeric-literals @gol
 -Wabi=@var{n}  -Wabi-tag  -Wconversion-null  -Wctor-dtor-privacy @gol
--Wdelete-non-virtual-dtor  -Wdeprecated-copy  -Wliteral-suffix @gol
+-Wdelete-non-virtual-dtor  -Wdeprecated-copy  -Wdeprecated-copy-dtor @gol
+-Wliteral-suffix @gol
 -Wmultiple-inheritance  -Wno-init-list-lifetime @gol
 -Wnamespaces  -Wnarrowing @gol
 -Wpessimizing-move  -Wredundant-move @gol
@@ -3000,8 +3001,10 @@ by @option{-Wall}.
 @opindex Wno-deprecated-copy
 Warn that the implicit declaration of a copy constructor or copy
 assignment operator is deprecated if the class has a user-provided
-copy constructor, copy assignment operator, or destructor, in C++11
-and up.  This warning is enabled by @option{-Wall}.
+copy constructor or copy assignment operator, in C++11 and up.  This
+warning is enabled by @option{-Wextra}.  With
+@option{-Wdeprecated-copy-dtor}, also deprecate if the class has a
+user-provided destructor.
 
 @item -Wno-init-list-lifetime @r{(C++ and Objective-C++ only)}
 @opindex Winit-list-lifetime
@@ -4407,6 +4410,7 @@ name is still supported, but the newer name is more descriptive.)
 
 @gccoptlist{-Wclobbered  @gol
 -Wcast-function-type  @gol
+-Wdeprecated-copy @r{(C++ only)} @gol
 -Wempty-body  @gol
 -Wignored-qualifiers @gol
 -Wimplicit-fallthrough=3 @gol
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 6f88a1013d6..07ff1c84f96 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -481,7 +481,12 @@ C C++ ObjC ObjC++ CPP(cpp_warn_deprecated) CppReason(CPP_W_DEPRECATED) Var(warn_
 Warn if a deprecated compiler feature, class, method, or field is used.
 
 Wdeprecated-copy
-C++ ObjC++ Var(warn_deprecated_copy) Warning LangEnabledBy(C++ ObjC++, Wall)
+C++ ObjC++ Var(warn_deprecated_copy) Warning LangEnabledBy(C++ ObjC++, Wextra)
+Mark implicitly-declared copy operations as deprecated if the class has a
+user-provided copy operation.
+
+Wdeprecated-copy-dtor
+C++ ObjC++ Var(warn_deprecated_copy, 2) Warning
 Mark implicitly-declared copy operations as deprecated if the class has a
 user-provided copy operation or destructor.
 
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 111a123bb34..886abeaa3f9 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6272,7 +6272,7 @@ extern bool type_has_constexpr_default_constructor (tree);
 extern bool type_has_virtual_destructor		(tree);
 extern bool classtype_has_move_assign_or_move_ctor_p (tree, bool user_declared);
 extern bool classtype_has_non_deleted_move_ctor (tree);
-extern tree classtype_has_user_copy_or_dtor	(tree);
+extern tree classtype_has_depr_implicit_copy	(tree);
 extern bool type_build_ctor_call		(tree);
 extern bool type_build_dtor_call		(tree);
 extern void explain_non_literal_class		(tree);
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index 57261511a90..9c175f85cf6 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -5233,7 +5233,7 @@ classtype_has_non_deleted_move_ctor (tree t)
    operator, or destructor, returns that function.  Otherwise, null.  */
 
 tree
-classtype_has_user_copy_or_dtor (tree t)
+classtype_has_depr_implicit_copy (tree t)
 {
   if (!CLASSTYPE_LAZY_COPY_CTOR (t))
     for (ovl_iterator iter (CLASSTYPE_CONSTRUCTORS (t)); iter; ++iter)
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index 79abdaebe86..44e6ef379ed 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -5275,18 +5275,23 @@ cp_warn_deprecated_use (tree decl, tsubst_flags_t complain)
       && DECL_NONSTATIC_MEMBER_FUNCTION_P (decl)
       && copy_fn_p (decl))
     {
-      auto_diagnostic_group d;
-      /* Don't warn about system library classes (c++/86342).  */
-      if (!DECL_IN_SYSTEM_HEADER (decl))
-	warned = warning (OPT_Wdeprecated_copy,
-			  "implicitly-declared %qD is deprecated", decl);
-      if (warned)
+      if (warn_deprecated_copy
+	  /* Don't warn about system library classes (c++/86342).  */
+	  && (!DECL_IN_SYSTEM_HEADER (decl)
+	      || global_dc->dc_warn_system_headers))
 	{
+	  auto_diagnostic_group d;
 	  tree ctx = DECL_CONTEXT (decl);
-	  tree other = classtype_has_user_copy_or_dtor (ctx);
-	  inform (DECL_SOURCE_LOCATION (other),
-		  "because %qT has user-provided %qD",
-		  ctx, other);
+	  tree other = classtype_has_depr_implicit_copy (ctx);
+	  int opt = (DECL_DESTRUCTOR_P (other)
+		     ? OPT_Wdeprecated_copy_dtor
+		     : OPT_Wdeprecated_copy);
+	  warned = warning (opt, "implicitly-declared %qD is deprecated",
+			    decl);
+	  if (warned)
+	    inform (DECL_SOURCE_LOCATION (other),
+		    "because %qT has user-provided %qD",
+		    ctx, other);
 	}
     }
   else
diff --git a/gcc/cp/method.c b/gcc/cp/method.c
index 936dad42122..fd023e20053 100644
--- a/gcc/cp/method.c
+++ b/gcc/cp/method.c
@@ -2380,7 +2380,7 @@ lazily_declare_fn (special_function_kind sfk, tree type)
     {
       if (classtype_has_move_assign_or_move_ctor_p (type, true))
 	DECL_DELETED_FN (fn) = true;
-      else if (classtype_has_user_copy_or_dtor (type))
+      else if (classtype_has_depr_implicit_copy (type))
 	/* The implicit definition of a copy constructor as defaulted is
 	   deprecated if the class has a user-declared copy assignment operator
 	   or a user-declared destructor. The implicit definition of a copy
diff --git a/gcc/testsuite/g++.dg/cpp0x/depr-copy1.C b/gcc/testsuite/g++.dg/cpp0x/depr-copy1.C
index d33c6dc667d..bbb81303925 100644
--- a/gcc/testsuite/g++.dg/cpp0x/depr-copy1.C
+++ b/gcc/testsuite/g++.dg/cpp0x/depr-copy1.C
@@ -6,7 +6,7 @@
    of this International Standard, these implicit definitions could become
    deleted (11.4).  */
 
-// { dg-additional-options -Wdeprecated-copy }
+// { dg-additional-options -Wdeprecated-copy-dtor }
 
 struct X
 {

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