Don't rely on the default constructor default constructing a begin and

end iterator for iterator_range<>. I removed this constructor because
for some iterators (notably pointers) it left begin and end
uninitialized. It also is an usual constraint that an iterator default
constructs to a valid end iterator such that the pair of them for
a valid range. In the three places where this was used in Clang,
explicitly build the empty range from the iterators and comment on why
default constructed iterators make sense here.

llvm-svn: 225594

2 files changed, 10 insertions, 3 deletions

diff --git a/clang/include/clang/AST/DeclLookups.h b/clang/include/clang/AST/DeclLookups.h
index d2016af89f1..eba2266724f 100644
--- a/clang/include/clang/AST/DeclLookups.h
+++ b/clang/include/clang/AST/DeclLookups.h
@@ -75,7 +75,10 @@ inline DeclContext::lookups_range DeclContext::lookups() const {
   if (StoredDeclsMap *Map = Primary->buildLookup())
     return lookups_range(all_lookups_iterator(Map->begin(), Map->end()),
                          all_lookups_iterator(Map->end(), Map->end()));
-  return lookups_range();
+
+  // Synthesize an empty range. This requires that two default constructed
+  // versions of these iterators form a valid empty range.
+  return lookups_range(all_lookups_iterator(), all_lookups_iterator());
 }
 
 inline DeclContext::all_lookups_iterator DeclContext::lookups_begin() const {
@@ -91,7 +94,10 @@ inline DeclContext::lookups_range DeclContext::noload_lookups() const {
   if (StoredDeclsMap *Map = Primary->getLookupPtr())
     return lookups_range(all_lookups_iterator(Map->begin(), Map->end()),
                          all_lookups_iterator(Map->end(), Map->end()));
-  return lookups_range();
+
+  // Synthesize an empty range. This requires that two default constructed
+  // versions of these iterators form a valid empty range.
+  return lookups_range(all_lookups_iterator(), all_lookups_iterator());
 }
 
 inline
diff --git a/clang/include/clang/AST/DependentDiagnostic.h b/clang/include/clang/AST/DependentDiagnostic.h
index 63066797b3a..8e038c83c98 100644
--- a/clang/include/clang/AST/DependentDiagnostic.h
+++ b/clang/include/clang/AST/DependentDiagnostic.h
@@ -178,7 +178,8 @@ inline DeclContext::ddiag_range DeclContext::ddiags() const {
     = static_cast<DependentStoredDeclsMap*>(getPrimaryContext()->getLookupPtr());
 
   if (!Map)
-    return ddiag_range();
+    // Return an empty range using the always-end default constructor.
+    return ddiag_range(ddiag_iterator(), ddiag_iterator());
 
   return ddiag_range(ddiag_iterator(Map->FirstDiagnostic), ddiag_iterator());
 }