shivanshu3 created this revision.
shivanshu3 added reviewers: zahen, tiagoma, rnk, hans.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
shivanshu3 requested review of this revision.
Goal: Clang should be able to parse the following code with
'-fms-compatibility' because MSVC allows using the 'enum' specifier for
typedef'd anonymous enums:
typedef enum
{
First,
Second
} MyEnum;
void func()
{
enum MyEnum foo;
}
Today the code above produces the following compile error:
<source>:9:7: error: typedef 'MyEnum' cannot be referenced with a enum
specifier
enum MyEnum foo;
^
<source>:5:3: note: declared here
} MyEnum;
^
The reason why this change is desired in Clang is because the MSVC tools
'mktyplib' and 'midl' produce C++ code which uses the 'enum' specifier in such
a way. Here is a small repro:
MyEnum.idl:
[
uuid(da2889bf-6173-4c1c-a23d-52ad85fc91ca)
]
library MyEnumLib
{
typedef enum { X } MyEnum;
};
Application.idl:
[
uuid(4d0cc96f-3258-46f7-98bf-6654c1d027c5)
]
library ApplicationLib
{
importlib("MyEnum.tlb");
[
uuid(6ac4c3d7-15c7-40c7-8b64-60459e29680b)
]
interface ApplicationInterface : IDispatch
{
[
id(66),
propget
]
HRESULT Foo([out, retval] enum MyEnum* Foo);
[
id(66),
propput
]
HRESULT Foo([in] enum MyEnum Foo);
};
};
Use the following commands to build:
mktyplib /win32 /cpp_cmd cl.exe /cpp_opt /E /tlb MyEnum.tlb /h MyEnum.h
MyEnum.idl
midl -h Application.h -iid Application.c -tlb Application.tlb /cpp_cmd cl.exe
Application.idl
This produces Application.h with the following snippet (note the usage of the
'enum' specifier):
MIDL_INTERFACE("6ac4c3d7-15c7-40c7-8b64-60459e29680b")
ApplicationInterface : public IDispatch
{
public:
virtual /* [propget][id] */ HRESULT STDMETHODCALLTYPE get_Foo(
/* [retval][out] */ enum /* external definition not present */ MyEnum
*Foo) = 0;
virtual /* [propput][id] */ HRESULT STDMETHODCALLTYPE put_Foo(
/* [in] */ enum /* external definition not present */ MyEnum Foo) = 0;
};
Note that the 'mktyplib' tool is deprecated now but it's used for building some
code here at Microsoft, and probably other legacy build scenarios in the
industry as well.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D91659
Files:
clang/lib/Sema/SemaDecl.cpp
clang/test/Sema/enum-typedef-msvc.c
clang/test/Sema/enum-typedef-msvc.cpp
Index: clang/test/Sema/enum-typedef-msvc.cpp
===================================================================
--- /dev/null
+++ clang/test/Sema/enum-typedef-msvc.cpp
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -fms-compatibility %s
+
+typedef enum {
+ First,
+ Second
+} MyEnum;
+
+class AMyInterface {
+ virtual void MyFunc(enum MyEnum *param) = 0;
+};
+
+class MyImpl : public AMyInterface {
+ virtual void MyFunc(enum MyEnum *param) override {}
+};
+
+// expected-no-diagnostics
Index: clang/test/Sema/enum-typedef-msvc.c
===================================================================
--- /dev/null
+++ clang/test/Sema/enum-typedef-msvc.c
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -fsyntax-only -verify -fms-compatibility -DUSE_MSVC_COMPAT
%s
+
+typedef enum {
+ A
+} Foo;
+
+void func() {
+#ifdef USE_MSVC_COMPAT
+ enum Foo foo; // expected-no-diagnostics
+#else
+ enum Foo foo; // expected-error {{variable has incomplete type 'enum Foo'}}
// expected-note {{forward declaration of 'enum Foo'}}
+#endif
+ (void)foo;
+}
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -15539,6 +15539,34 @@
// shouldn't be diagnosing.
LookupName(Previous, S);
+ // Under MSVC, the 'enum' specifier can be used for typedef'd enums.
+ // Note that lookup only fails in C, not C++, so this if condition
+ // is only used for C code.
+ if (getLangOpts().MSVCCompat && (Kind == TTK_Enum) && Previous.empty() &&
+ (TUK == TUK_Reference)) {
+ LookupResult TypedefEnumLookup(*this, Name, NameLoc, LookupOrdinaryName,
+ Redecl);
+ LookupName(TypedefEnumLookup, S);
+
+ if (!TypedefEnumLookup.empty()) {
+ if (TypedefNameDecl *TD =
+ dyn_cast<TypedefNameDecl>(TypedefEnumLookup.getFoundDecl())) {
+ const Type *UnderlyingTypePtr =
+ TD->getUnderlyingType().getTypePtrOrNull();
+
+ if (UnderlyingTypePtr) {
+ if (EnumDecl *UnderlyingEnumDecl =
+ dyn_cast<EnumDecl>(UnderlyingTypePtr->getAsTagDecl())) {
+ // We only allow this for anonymous enums
+ if (UnderlyingEnumDecl->getDeclName().isEmpty()) {
+ Previous.addDecl(UnderlyingEnumDecl);
+ }
+ }
+ }
+ }
+ }
+ }
+
// When declaring or defining a tag, ignore ambiguities introduced
// by types using'ed into this scope.
if (Previous.isAmbiguous() &&
@@ -15721,9 +15749,12 @@
if (TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(PrevDecl)) {
if (const TagType *TT = TD->getUnderlyingType()->getAs<TagType>()) {
TagDecl *Tag = TT->getDecl();
- if (Tag->getDeclName() == Name &&
- Tag->getDeclContext()->getRedeclContext()
- ->Equals(TD->getDeclContext()->getRedeclContext())) {
+ bool AnonymousEnumEligible = getLangOpts().MSVCCompat &&
+ (Kind == TTK_Enum) &&
+ Tag->getDeclName().isEmpty();
+ if ((Tag->getDeclName() == Name || AnonymousEnumEligible) &&
+ Tag->getDeclContext()->getRedeclContext()->Equals(
+ TD->getDeclContext()->getRedeclContext())) {
PrevDecl = Tag;
Previous.clear();
Previous.addDecl(Tag);
Index: clang/test/Sema/enum-typedef-msvc.cpp
===================================================================
--- /dev/null
+++ clang/test/Sema/enum-typedef-msvc.cpp
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -fms-compatibility %s
+
+typedef enum {
+ First,
+ Second
+} MyEnum;
+
+class AMyInterface {
+ virtual void MyFunc(enum MyEnum *param) = 0;
+};
+
+class MyImpl : public AMyInterface {
+ virtual void MyFunc(enum MyEnum *param) override {}
+};
+
+// expected-no-diagnostics
Index: clang/test/Sema/enum-typedef-msvc.c
===================================================================
--- /dev/null
+++ clang/test/Sema/enum-typedef-msvc.c
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -fsyntax-only -verify -fms-compatibility -DUSE_MSVC_COMPAT %s
+
+typedef enum {
+ A
+} Foo;
+
+void func() {
+#ifdef USE_MSVC_COMPAT
+ enum Foo foo; // expected-no-diagnostics
+#else
+ enum Foo foo; // expected-error {{variable has incomplete type 'enum Foo'}} // expected-note {{forward declaration of 'enum Foo'}}
+#endif
+ (void)foo;
+}
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -15539,6 +15539,34 @@
// shouldn't be diagnosing.
LookupName(Previous, S);
+ // Under MSVC, the 'enum' specifier can be used for typedef'd enums.
+ // Note that lookup only fails in C, not C++, so this if condition
+ // is only used for C code.
+ if (getLangOpts().MSVCCompat && (Kind == TTK_Enum) && Previous.empty() &&
+ (TUK == TUK_Reference)) {
+ LookupResult TypedefEnumLookup(*this, Name, NameLoc, LookupOrdinaryName,
+ Redecl);
+ LookupName(TypedefEnumLookup, S);
+
+ if (!TypedefEnumLookup.empty()) {
+ if (TypedefNameDecl *TD =
+ dyn_cast<TypedefNameDecl>(TypedefEnumLookup.getFoundDecl())) {
+ const Type *UnderlyingTypePtr =
+ TD->getUnderlyingType().getTypePtrOrNull();
+
+ if (UnderlyingTypePtr) {
+ if (EnumDecl *UnderlyingEnumDecl =
+ dyn_cast<EnumDecl>(UnderlyingTypePtr->getAsTagDecl())) {
+ // We only allow this for anonymous enums
+ if (UnderlyingEnumDecl->getDeclName().isEmpty()) {
+ Previous.addDecl(UnderlyingEnumDecl);
+ }
+ }
+ }
+ }
+ }
+ }
+
// When declaring or defining a tag, ignore ambiguities introduced
// by types using'ed into this scope.
if (Previous.isAmbiguous() &&
@@ -15721,9 +15749,12 @@
if (TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(PrevDecl)) {
if (const TagType *TT = TD->getUnderlyingType()->getAs<TagType>()) {
TagDecl *Tag = TT->getDecl();
- if (Tag->getDeclName() == Name &&
- Tag->getDeclContext()->getRedeclContext()
- ->Equals(TD->getDeclContext()->getRedeclContext())) {
+ bool AnonymousEnumEligible = getLangOpts().MSVCCompat &&
+ (Kind == TTK_Enum) &&
+ Tag->getDeclName().isEmpty();
+ if ((Tag->getDeclName() == Name || AnonymousEnumEligible) &&
+ Tag->getDeclContext()->getRedeclContext()->Equals(
+ TD->getDeclContext()->getRedeclContext())) {
PrevDecl = Tag;
Previous.clear();
Previous.addDecl(Tag);
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