Add extension to always default-initialize nullptr_t.
Core issue 1013 suggests that having an uninitialied std::nullptr_t be
UB is a bit foolish, since there is only a single valid value. This DR
reports that DR616 fixes it, which does so by making lvalue-to-rvalue
conversions from nullptr_t be equal to nullptr.
However, just implementing that results in warnings/etc in many places.
In order to fix all situations where nullptr_t would seem uninitialized,
this patch instead (as an otherwise transparent extension) default
initializes uninitialized VarDecls of nullptr_t.
Differential Revision: https://reviews.llvm.org/D53713
Change-Id: I84d72a9290054fa55341e8cbdac43c8e7f25b885
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@349201 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaInit.cpp b/lib/Sema/SemaInit.cpp
index c2f1422..57277f6 100644
--- a/lib/Sema/SemaInit.cpp
+++ b/lib/Sema/SemaInit.cpp
@@ -4881,6 +4881,13 @@
return;
}
+ // As an extension, and to fix Core issue 1013, zero initialize nullptr_t.
+ // Since there is only 1 valid value of nullptr_t, we can just use that.
+ if (DestType->isNullPtrType()) {
+ Sequence.AddZeroInitializationStep(Entity.getType());
+ return;
+ }
+
// - otherwise, no initialization is performed.
// If a program calls for the default initialization of an object of
diff --git a/test/Analysis/nullptr.cpp b/test/Analysis/nullptr.cpp
index 38e099b..1d913c1 100644
--- a/test/Analysis/nullptr.cpp
+++ b/test/Analysis/nullptr.cpp
@@ -125,21 +125,16 @@
};
void shouldNotCrash() {
- decltype(nullptr) p; // expected-note{{'p' declared without an initial value}}
- if (getSymbol()) // expected-note {{Assuming the condition is false}}
- // expected-note@-1{{Taking false branch}}
- // expected-note@-2{{Assuming the condition is false}}
- // expected-note@-3{{Taking false branch}}
- // expected-note@-4{{Assuming the condition is true}}
- // expected-note@-5{{Taking true branch}}
- invokeF(p); // expected-warning{{1st function call argument is an uninitialized value}}
- // expected-note@-1{{1st function call argument is an uninitialized value}}
+ decltype(nullptr) p; // expected-note{{'p' initialized to a null pointer value}}
if (getSymbol()) // expected-note {{Assuming the condition is false}}
// expected-note@-1{{Taking false branch}}
// expected-note@-2{{Assuming the condition is true}}
// expected-note@-3{{Taking true branch}}
- invokeF(nullptr); // expected-note {{Calling 'invokeF'}}
- // expected-note@-1{{Passing null pointer value via 1st parameter 'x'}}
+ invokeF(p); // expected-note{{Passing null pointer value via 1st parameter 'x'}}
+ // expected-note@-1{{Calling 'invokeF'}}
+ if (getSymbol()) // expected-note {{Assuming the condition is false}}
+ // expected-note@-1{{Taking false branch}}
+ invokeF(nullptr);
if (getSymbol()) { // expected-note {{Assuming the condition is true}}
// expected-note@-1{{Taking true branch}}
X *xx = Type().x; // expected-note {{Null pointer value stored to field 'x'}}
diff --git a/test/SemaCXX/ast-print-crash.cpp b/test/SemaCXX/ast-print-crash.cpp
index c108f66..33edc34 100644
--- a/test/SemaCXX/ast-print-crash.cpp
+++ b/test/SemaCXX/ast-print-crash.cpp
@@ -7,6 +7,6 @@
// CHECK: struct {
// CHECK-NEXT: } dont_crash_on_syntax_error;
-// CHECK-NEXT: decltype(nullptr) p;
+// CHECK-NEXT: decltype(nullptr) p(/*implicit*/(decltype(nullptr))0);
struct {
} dont_crash_on_syntax_error /* missing ; */ decltype(nullptr) p;
diff --git a/test/SemaCXX/nullptr_t-init.cpp b/test/SemaCXX/nullptr_t-init.cpp
new file mode 100644
index 0000000..f7843de
--- /dev/null
+++ b/test/SemaCXX/nullptr_t-init.cpp
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -ffreestanding -Wuninitialized %s
+// expected-no-diagnostics
+typedef decltype(nullptr) nullptr_t;
+
+// Ensure no 'uninitialized when used here' warnings (Wuninitialized), for
+// nullptr_t always-initialized extension.
+nullptr_t default_init() {
+ nullptr_t a;
+ return a;
+}
