[lldb] Enable C++14 when evaluating expressions in a C++14 frame

Summary:
Currently we never enable C++14 in the expression evaluator. This enables it when the language of the program is C++14.

It seems C++17 and so on isn't yet in any of the language enums (and the DWARF standard it seems), so C++17 support will be a follow up patch.

Reviewers: labath, JDevlieghere

Reviewed By: labath, JDevlieghere

Subscribers: aprantl

Differential Revision: https://reviews.llvm.org/D80308

Author: Teemperor

lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp

@@ -491,9 +491,11 @@ ClangExpressionParser::ClangExpressionParser(
     // be re-evaluated in the future.
     lang_opts.CPlusPlus11 = true;
     break;
+  case lldb::eLanguageTypeC_plus_plus_14:
+    lang_opts.CPlusPlus14 = true;
+    LLVM_FALLTHROUGH;
   case lldb::eLanguageTypeC_plus_plus:
   case lldb::eLanguageTypeC_plus_plus_11:
-  case lldb::eLanguageTypeC_plus_plus_14:
     lang_opts.CPlusPlus11 = true;
     m_compiler->getHeaderSearchOpts().UseLibcxx = true;
     LLVM_FALLTHROUGH;

lldb/test/API/lang/cpp/standards/cpp11/Makefile

@@ -0,0 +1,4 @@
+CXX_SOURCES := main.cpp
+CXXFLAGS_EXTRAS := -std=c++11
+
+include Makefile.rules

lldb/test/API/lang/cpp/standards/cpp11/TestCPP11Standard.py

@@ -0,0 +1,19 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+class TestCase(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    def test(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, "// break here", lldb.SBFileSpec("main.cpp"))
+
+        # Run an expression that is valid in C++11 (as it uses nullptr).
+        self.expect_expr("nullptr == nullptr", result_type="bool", result_value="true")
+
+        # Run a expression that is not valid in C++11 (as it uses polymorphic
+        # lambdas from C++14).
+        self.expect("expr [](auto x) { return x; }(1)", error=True, substrs=["'auto' not allowed in lambda parameter"])

lldb/test/API/lang/cpp/standards/cpp11/main.cpp

@@ -0,0 +1,3 @@
+int main() {
+  return 0; // break here
+}

lldb/test/API/lang/cpp/standards/cpp14/Makefile

@@ -0,0 +1,4 @@
+CXX_SOURCES := main.cpp
+CXXFLAGS_EXTRAS := -std=c++14
+
+include Makefile.rules

lldb/test/API/lang/cpp/standards/cpp14/TestCPP14Standard.py

@@ -0,0 +1,19 @@
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+class TestCase(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    def test(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, "// break here", lldb.SBFileSpec("main.cpp"))
+
+        # Run an expression that is valid in C++11 (as it uses nullptr).
+        self.expect_expr("nullptr == nullptr", result_type="bool", result_value="true")
+
+        # Run a expression that is only valid in C++14 that (as it uses
+        # polymorphic lambdas).
+        self.expect_expr("[](auto x) { return x; }(1)", result_type="int", result_value="1")

lldb/test/API/lang/cpp/standards/cpp14/main.cpp

@@ -0,0 +1,3 @@
+int main() {
+  return 0; // break here
+}