[PATCH] Fix linkage calculation of auto member functions returning lambdas
Faisal Vali
faisalv at yahoo.com
Sat Oct 5 09:21:18 PDT 2013
Hi rsmith, doug.gregor,
As described by Richard in https://groups.google.com/a/isocpp.org/d/msg/std-discussion/S1kmj0wF5-g/fb6agEYoL2IJ
we should allow:
template<typename S>
struct A {
template<typename T> static auto default_lambda() {
return [](const T&) { return 42; };
}
template<class U = decltype(default_lambda<S>())>
U func(U u = default_lambda<S>()) { return u; }
};
int run2 = A<double>{}.func()(3.14);
int run3 = A<char>{}.func()('a');
This patch allows the code using the same trickery that was used to allow the code in non-member functions at namespace scope.
http://llvm-reviews.chandlerc.com/D1844
Files:
lib/AST/Decl.cpp
test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp
Index: lib/AST/Decl.cpp
===================================================================
--- lib/AST/Decl.cpp
+++ lib/AST/Decl.cpp
@@ -698,8 +698,8 @@
// require looking at the linkage of this function, and we don't need this
// for correctness because the type is not part of the function's
// signature.
- // FIXME: This is a hack. We should be able to solve this circularity some
- // other way.
+ // FIXME: This is a hack. We should be able to solve this circularity and
+ // the one in getLVForClassMember for Functions some other way.
QualType TypeAsWritten = Function->getType();
if (TypeSourceInfo *TSI = Function->getTypeSourceInfo())
TypeAsWritten = TSI->getType();
@@ -826,9 +826,20 @@
if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(D)) {
// If the type of the function uses a type with unique-external
// linkage, it's not legally usable from outside this translation unit.
- if (MD->getType()->getLinkage() == UniqueExternalLinkage)
- return LinkageInfo::uniqueExternal();
-
+ // But only look at the type-as-written. If this function has an auto-deduced
+ // return type, we can't compute the linkage of that type because it could
+ // require looking at the linkage of this function, and we don't need this
+ // for correctness because the type is not part of the function's
+ // signature.
+ // FIXME: This is a hack. We should be able to solve this circularity and the
+ // one in getLVForNamespaceScopeDecl for Functions some other way.
+ {
+ QualType TypeAsWritten = MD->getType();
+ if (TypeSourceInfo *TSI = MD->getTypeSourceInfo())
+ TypeAsWritten = TSI->getType();
+ if (TypeAsWritten->getLinkage() == UniqueExternalLinkage)
+ return LinkageInfo::uniqueExternal();
+ }
// If this is a method template specialization, use the linkage for
// the template parameters and arguments.
if (FunctionTemplateSpecializationInfo *spec
Index: test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp
===================================================================
--- test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp
+++ test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp
@@ -0,0 +1,77 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10.0.0 -fblocks -emit-llvm -o - %s -fexceptions -std=c++1y | FileCheck %s
+
+// CHECK-LABEL: define void @_ZN19non_inline_function3fooEv
+// CHECK-LABEL: define internal void @"_ZZN19non_inline_function3fooEvENK3$_0clEi"(%class.anon
+// CHECK-LABEL: define internal signext i8 @"_ZZZN19non_inline_function3fooEvENK3$_0clEiENKUlcE_clEc"(%class.anon
+// CHECK-LABEL: define linkonce_odr void @_ZN19non_inline_function4foo2IiEEDav()
+namespace non_inline_function {
+auto foo() {
+ auto L = [](int a) {
+ return [](char b) {
+ return b;
+ };
+ };
+ L(3)('a');
+ return L;
+}
+
+template<typename T>
+auto foo2() {
+ return [](const T&) { return 42; };
+}
+
+auto use = foo2<int>();
+
+}
+//CHECK-LABEL: define linkonce_odr void @_ZN22inline_member_function1X3fooEv(%"struct.inline_member_function::X"* %this)
+//CHECK-LABEL: define linkonce_odr void @_ZZN22inline_member_function1X3fooEvENKUliE_clEi(%class.anon
+//CHECK-LABEL: define linkonce_odr signext i8 @_ZZZN22inline_member_function1X3fooEvENKUliE_clEiENKUlcE_clEc(%class.anon
+
+namespace inline_member_function {
+struct X {
+auto foo() {
+ auto L = [](int a) {
+ return [](char b) {
+ return b;
+ };
+ };
+ return L;
+}
+};
+
+auto run1 = X{}.foo()(3)('a');
+
+template<typename S>
+struct A {
+ template<typename T> static auto default_lambda() {
+ return [](const T&) { return 42; };
+ }
+
+ template<class U = decltype(default_lambda<S>())>
+ U func(U u = default_lambda<S>()) { return u; }
+
+ template<class T> auto foo() { return [](const T&) { return 42; }; }
+};
+//CHECK-LABEL: define linkonce_odr i32 @_ZZN22inline_member_function1AIdE14default_lambdaIdEEDavENKUlRKdE_clES5_(%class.anon
+int run2 = A<double>{}.func()(3.14);
+
+//CHECK-LABEL: define linkonce_odr i32 @_ZZN22inline_member_function1AIcE14default_lambdaIcEEDavENKUlRKcE_clES5_(%class.anon
+int run3 = A<char>{}.func()('a');
+} // end inline_member_function
+
+
+// CHECK-LABEL: define linkonce_odr void @_ZN15inline_function3fooEv()
+// CHECK: define linkonce_odr void @_ZZN15inline_function3fooEvENKUliE_clEi(%class.anon
+// CHECK: define linkonce_odr signext i8 @_ZZZN15inline_function3fooEvENKUliE_clEiENKUlcE_clEc(%class.anon
+namespace inline_function {
+inline auto foo() {
+ auto L = [](int a) {
+ return [](char b) {
+ return b;
+ };
+ };
+ return L;
+}
+auto use = foo()(3)('a');
+}
+
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