[PATCH] D20365: [PATCH] clang-tidy: Bug 27731 - modernize-pass-by-value suggest using std::move for types that perform copies on move

[Mads Ravn via cfe-commits]

madsravn created this revision.
madsravn added reviewers: alexfh, vsk, djasper, klimek.
madsravn added a subscriber: cfe-commits.

This is a patch for bug: https://llvm.org/bugs/show_bug.cgi?id=27731

I have excluded types which are trivially copyable from being called with 
std::move in the modernizer. In the current state another modernizer will catch 
them and change them back, thus creating a cyclic behaviour.

http://reviews.llvm.org/D20365

Files:
  clang-tidy/modernize/PassByValueCheck.cpp
  test/clang-tidy/modernize-pass-by-value.cpp

Index: test/clang-tidy/modernize-pass-by-value.cpp
===================================================================
--- test/clang-tidy/modernize-pass-by-value.cpp
+++ test/clang-tidy/modernize-pass-by-value.cpp
@@ -194,3 +194,9 @@
   Movable M;
 };
 
+// Test that types that are trivially copyable will not use std::move. This 
will
+// cause problems with misc-move-const-arg, as it will revert it.
+struct T {
+  std::array<int, 10> a_;
+  T(std::array<int, 10> a) : a_(a) {}
+};
Index: clang-tidy/modernize/PassByValueCheck.cpp
===================================================================
--- clang-tidy/modernize/PassByValueCheck.cpp
+++ clang-tidy/modernize/PassByValueCheck.cpp
@@ -181,6 +181,11 @@
   if (!paramReferredExactlyOnce(Ctor, ParamDecl))
     return;
 
+  // If the parameter is trivial to copy, don't move it. Moving a trivivally
+  // copyable type will cause a problem with modernize-pass-by-value
+  if (ParamDecl->getType().isTriviallyCopyableType(*Result.Context)) 
+    return;
+
   auto Diag = diag(ParamDecl->getLocStart(), "pass by value and use 
std::move");
 
   // Iterate over all declarations of the constructor.



Index: test/clang-tidy/modernize-pass-by-value.cpp
===================================================================
--- test/clang-tidy/modernize-pass-by-value.cpp
+++ test/clang-tidy/modernize-pass-by-value.cpp
@@ -194,3 +194,9 @@
   Movable M;
 };
 
+// Test that types that are trivially copyable will not use std::move. This will
+// cause problems with misc-move-const-arg, as it will revert it.
+struct T {
+  std::array<int, 10> a_;
+  T(std::array<int, 10> a) : a_(a) {}
+};
Index: clang-tidy/modernize/PassByValueCheck.cpp
===================================================================
--- clang-tidy/modernize/PassByValueCheck.cpp
+++ clang-tidy/modernize/PassByValueCheck.cpp
@@ -181,6 +181,11 @@
   if (!paramReferredExactlyOnce(Ctor, ParamDecl))
     return;
 
+  // If the parameter is trivial to copy, don't move it. Moving a trivivally
+  // copyable type will cause a problem with modernize-pass-by-value
+  if (ParamDecl->getType().isTriviallyCopyableType(*Result.Context)) 
+    return;
+
   auto Diag = diag(ParamDecl->getLocStart(), "pass by value and use std::move");
 
   // Iterate over all declarations of the constructor.

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