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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

llvm-svn: 335082
This commit is contained in:
Nico Weber 2018-06-19 23:19:34 +00:00
parent 1f79297ebe
commit 3d7f00d25b
2 changed files with 40 additions and 19 deletions
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42
clang/lib/Sema/SemaInit.cpp
View File

@ -8331,6 +8331,11 @@ void InitializationSequence::dump() const {
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 @@ static void DiagnoseNarrowingInInitList(Sema &S,
// 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;
}

17
clang/test/SemaCXX/ms-initlist-narrowing.cpp Normal file
View File

@ -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}}
}