commit c3261ea295e010b1720e19b4ddd05b966366fea1
author Nico Weber <nicolasweber@gmx.de> Tue Jun 19 23:19:34 2018 +0000
committer Nico Weber <nicolasweber@gmx.de> Tue Jun 19 23:19:34 2018 +0000
tree dc229c05de0d62f289366ba2a34203cb0dfbd513
parent cd6d4e81a71e04a91eb93878a4668844e1d2162b

clang-cl: Emit narrowing diag for initializer lists if -fmsc-version is at least 1900 (i.e. MSVC2015).

Diagnostics for narrowing conversions in initializer lists are currently
DefaultIgnored in Microsoft mode. But MSVC 2015 did add warnings about
narrowing conversions (C2397), so clang-cl can remove its special case code if
MSCompatibilityVersion is new enough.

(In MSVC, C2397 is just a warning and in clang it's default-mapped to an error,
but it can be remapped, and disabled with -Wno-c++11-narrowing, so that should
be fine.)

Fixes PR37314.
https://reviews.llvm.org/D48296


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@335082 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/SemaInit.cpp

diff --git a/lib/Sema/SemaInit.cpp b/lib/Sema/SemaInit.cpp
index dc9e298..cd6683e 100644
--- a/lib/Sema/SemaInit.cpp
+++ b/lib/Sema/SemaInit.cpp
@@ -8331,6 +8331,11 @@
   dump(llvm::errs());
 }
 
+static bool NarrowingErrs(const LangOptions &L) {
+  return L.CPlusPlus11 &&
+         (!L.MicrosoftExt || L.isCompatibleWithMSVC(LangOptions::MSVC2015));
+}
+
 static void DiagnoseNarrowingInInitList(Sema &S,
                                         const ImplicitConversionSequence &ICS,
                                         QualType PreNarrowingType,
@@ -8364,35 +8369,34 @@
     // This was a floating-to-integer conversion, which is always considered a
     // narrowing conversion even if the value is a constant and can be
     // represented exactly as an integer.
-    S.Diag(PostInit->getLocStart(),
-           (S.getLangOpts().MicrosoftExt || !S.getLangOpts().CPlusPlus11)
-               ? diag::warn_init_list_type_narrowing
-               : diag::ext_init_list_type_narrowing)
-      << PostInit->getSourceRange()
-      << PreNarrowingType.getLocalUnqualifiedType()
-      << EntityType.getLocalUnqualifiedType();
+    S.Diag(PostInit->getLocStart(), NarrowingErrs(S.getLangOpts())
+                                        ? diag::ext_init_list_type_narrowing
+                                        : diag::warn_init_list_type_narrowing)
+        << PostInit->getSourceRange()
+        << PreNarrowingType.getLocalUnqualifiedType()
+        << EntityType.getLocalUnqualifiedType();
     break;
 
   case NK_Constant_Narrowing:
     // A constant value was narrowed.
     S.Diag(PostInit->getLocStart(),
-           (S.getLangOpts().MicrosoftExt || !S.getLangOpts().CPlusPlus11)
-               ? diag::warn_init_list_constant_narrowing
-               : diag::ext_init_list_constant_narrowing)
-      << PostInit->getSourceRange()
-      << ConstantValue.getAsString(S.getASTContext(), ConstantType)
-      << EntityType.getLocalUnqualifiedType();
+           NarrowingErrs(S.getLangOpts())
+               ? diag::ext_init_list_constant_narrowing
+               : diag::warn_init_list_constant_narrowing)
+        << PostInit->getSourceRange()
+        << ConstantValue.getAsString(S.getASTContext(), ConstantType)
+        << EntityType.getLocalUnqualifiedType();
     break;
 
   case NK_Variable_Narrowing:
     // A variable's value may have been narrowed.
     S.Diag(PostInit->getLocStart(),
-           (S.getLangOpts().MicrosoftExt || !S.getLangOpts().CPlusPlus11)
-               ? diag::warn_init_list_variable_narrowing
-               : diag::ext_init_list_variable_narrowing)
-      << PostInit->getSourceRange()
-      << PreNarrowingType.getLocalUnqualifiedType()
-      << EntityType.getLocalUnqualifiedType();
+           NarrowingErrs(S.getLangOpts())
+               ? diag::ext_init_list_variable_narrowing
+               : diag::warn_init_list_variable_narrowing)
+        << PostInit->getSourceRange()
+        << PreNarrowingType.getLocalUnqualifiedType()
+        << EntityType.getLocalUnqualifiedType();
     break;
   }
 

test/SemaCXX/ms-initlist-narrowing.cpp

diff --git a/test/SemaCXX/ms-initlist-narrowing.cpp b/test/SemaCXX/ms-initlist-narrowing.cpp
new file mode 100644
index 0000000..687a206
--- /dev/null
+++ b/test/SemaCXX/ms-initlist-narrowing.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 %s -fsyntax-only -verify -fms-extensions -fms-compatibility-version=19.0 -std=c++11
+
+int ai[] = { 1, 2.0 };  // expected-error {{type 'double' cannot be narrowed to 'int' in initializer list}} expected-note {{silence}}
+
+template<typename T>
+struct Agg {
+  T t;
+};
+
+void f(int i) {
+  // Constant expression.
+  Agg<float> f8 = {1E50};  // expected-error {{constant expression evaluates to 1.000000e+50 which cannot be narrowed to type 'float'}} expected-note {{silence}}
+
+  // Non-constant expression.
+  double d = 1.0;
+  Agg<float> f2 = {d};  // expected-error {{non-constant-expression cannot be narrowed from type 'double' to 'float'}} expected-note {{silence}}
+}