tbaeder created this revision.
tbaeder added a reviewer: aaron.ballman.
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tbaeder requested review of this revision.
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Consider:
constexpr int a;
the error message for this is currently:
error: default initialization of an object of const type 'const int'
constexpr int a;
^
= 0
which makes very little sense to me. With this patch, the output is instead:
error: constexpr variable 'a' must be initialized by a constant expression
constexpr int a;
^
= 0
which is much better. Tells the user exactly what is missing.
For
constexpr int a[];
before this patch, the output is:
error: definition of variable with array type needs an explicit size or an
initializer
constexpr int a[];
^
The error message is not even true in this case, since _only_ passing a size
won't work. It must be initialized by a constant expression, so now the error
message is:
error: constexpr variable 'a' must be initialized by a constant expression
constexpr int a[];
^
and a fixit hint if a size was provided:
error: constexpr variable 'a' must be initialized by a constant expression
constexpr int a[2];
^
= {}
(not sure about that part)
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D131662
Files:
clang/lib/Sema/SemaDecl.cpp
clang/lib/Sema/SemaFixItUtils.cpp
clang/lib/Sema/SemaInit.cpp
clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p1.cpp
clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p9.cpp
clang/test/SemaCXX/constant-expression-cxx11.cpp
Index: clang/test/SemaCXX/constant-expression-cxx11.cpp
===================================================================
--- clang/test/SemaCXX/constant-expression-cxx11.cpp
+++ clang/test/SemaCXX/constant-expression-cxx11.cpp
@@ -27,6 +27,10 @@
constexpr int zero() const { return 0; }
};
+constexpr int arr[]; // expected-error {{constexpr variable 'arr' must be initialized by a constant expression}}
+constexpr int arr2[2]; // expected-error {{constexpr variable 'arr2' must be initialized by a constant expression}}
+constexpr int arr3[2] = {};
+
namespace DerivedToVBaseCast {
struct U { int n; };
@@ -1298,7 +1302,7 @@
void f() {
extern constexpr int i; // expected-error {{constexpr variable declaration must be a definition}}
constexpr int j = 0;
- constexpr int k; // expected-error {{default initialization of an object of const type}}
+ constexpr int k; // expected-error {{constexpr variable 'k' must be initialized by a constant expression}}
}
extern const int q;
Index: clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p9.cpp
===================================================================
--- clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p9.cpp
+++ clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p9.cpp
@@ -18,7 +18,7 @@
// A variable declaration which uses the constexpr specifier shall have an
// initializer and shall be initialized by a constant expression.
-constexpr int ni1; // expected-error {{default initialization of an object of const type 'const int'}}
+constexpr int ni1; // expected-error {{constexpr variable 'ni1' must be initialized by a constant expression}}
constexpr struct C { C(); } ni2; // expected-error {{cannot have non-literal type 'const struct C'}} expected-note 3{{has no constexpr constructors}}
constexpr double &ni3; // expected-error {{declaration of reference variable 'ni3' requires an initializer}}
Index: clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p1.cpp
===================================================================
--- clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p1.cpp
+++ clang/test/CXX/dcl.dcl/dcl.spec/dcl.constexpr/p1.cpp
@@ -37,7 +37,7 @@
#if __cplusplus <= 201402L && !defined(MS_ABI)
// expected-error@-2 {{requires an initializer}}
#else
- // expected-error@-4 {{default initialization of an object of const}}
+ // expected-error@-4 {{constexpr variable 'mi2' must be initialized by a constant expression}}
#endif
mutable constexpr int mi3 = 3; // expected-error-re {{non-static data member cannot be constexpr{{$}}}} expected-error {{'mutable' and 'const' cannot be mixed}}
};
Index: clang/lib/Sema/SemaInit.cpp
===================================================================
--- clang/lib/Sema/SemaInit.cpp
+++ clang/lib/Sema/SemaInit.cpp
@@ -8053,19 +8053,29 @@
return ExprError();
}
if (!ZeroInitializationFixit.empty()) {
- unsigned DiagID = diag::err_default_init_const;
- if (Decl *D = Entity.getDecl())
- if (S.getLangOpts().MSVCCompat && D->hasAttr<SelectAnyAttr>())
- DiagID = diag::ext_default_init_const;
+ const Decl *D = Entity.getDecl();
+ const VarDecl *VD = dyn_cast_or_null<VarDecl>(D);
+ QualType DestType = Entity.getType();
// The initialization would have succeeded with this fixit. Since the fixit
// is on the error, we need to build a valid AST in this case, so this isn't
// handled in the Failed() branch above.
- QualType DestType = Entity.getType();
- S.Diag(Kind.getLocation(), DiagID)
- << DestType << (bool)DestType->getAs<RecordType>()
- << FixItHint::CreateInsertion(ZeroInitializationFixitLoc,
- ZeroInitializationFixit);
+ if (!DestType->getAs<RecordType>() && VD && VD->isConstexpr()) {
+ // Use a more useful diagnostic for constexpr variables.
+ S.Diag(Kind.getLocation(), diag::err_constexpr_var_requires_const_init)
+ << VD
+ << FixItHint::CreateInsertion(ZeroInitializationFixitLoc,
+ ZeroInitializationFixit);
+ } else {
+ unsigned DiagID = diag::err_default_init_const;
+ if (S.getLangOpts().MSVCCompat && D && D->hasAttr<SelectAnyAttr>())
+ DiagID = diag::ext_default_init_const;
+
+ S.Diag(Kind.getLocation(), DiagID)
+ << DestType << (bool)DestType->getAs<RecordType>()
+ << FixItHint::CreateInsertion(ZeroInitializationFixitLoc,
+ ZeroInitializationFixit);
+ }
}
if (getKind() == DependentSequence) {
Index: clang/lib/Sema/SemaFixItUtils.cpp
===================================================================
--- clang/lib/Sema/SemaFixItUtils.cpp
+++ clang/lib/Sema/SemaFixItUtils.cpp
@@ -205,6 +205,10 @@
return s;
}
+ if (T->isArrayType()) {
+ return " = {}";
+ }
+
const CXXRecordDecl *RD = T->getAsCXXRecordDecl();
if (!RD || !RD->hasDefinition())
return std::string();
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -13363,8 +13363,12 @@
// Provide a specific diagnostic for uninitialized variable
// definitions with incomplete array type.
if (Type->isIncompleteArrayType()) {
- Diag(Var->getLocation(),
- diag::err_typecheck_incomplete_array_needs_initializer);
+ if (Var->isConstexpr())
+ Diag(Var->getLocation(), diag::err_constexpr_var_requires_const_init)
+ << Var;
+ else
+ Diag(Var->getLocation(),
+ diag::err_typecheck_incomplete_array_needs_initializer);
Var->setInvalidDecl();
return;
}
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