[C++][Frontend] Add translation for nullptr

Summary:
@public
Make c frontend understand CXXNullPtrLiteralExpr.
Note that the implementation differs from GNUNullExpr

Test Plan:
Create function that returns nullptr:
  int* getPtr() {return nullptr;}
look at specs:
  InferPrint infer-out/specs/getPtr\{831F\}.specs
  Procedure: getPtr
  int *getPtr()
  Timestamp: 1
  Status: INACTIVE
  Phase: RE_EXECUTION
  Dependency_map:
  TIME:0.002853 s TIMEOUT:N SYMOPS:10 CALLS:1,0
  ERRORS:
  --------------------------- 1 of 1 [nvisited: 1] ---------------------------
  PRE:

  POST 1 of 1:
  return = null:
  ----------------------------------------------------------------

Add test for it

infer/src/clang/cTrans.ml

@@ -189,6 +189,11 @@ struct
     let exp = Sil.Const (Sil.Cint (Sil.Int.zero)) in
     { empty_res_trans with exps = [(exp, typ)]}
 
+  let nullPtrExpr_trans trans_state stmt_info expr_info =
+    Printing.log_out "Passing from nullptr '%s'\n" stmt_info.Clang_ast_t.si_pointer;
+    let typ = CTypes_decl.get_type_from_expr_info expr_info trans_state.context.tenv in
+    { empty_res_trans with exps = [(Sil.exp_null, typ)]}
+
   let objCSelectorExpr_trans trans_state stmt_info expr_info selector =
     stringLiteral_trans trans_state stmt_info expr_info selector
 
@@ -1708,6 +1713,9 @@ struct
     | GNUNullExpr(stmt_info, stmt_list, expr_info) ->
         gNUNullExpr_trans trans_state stmt_info expr_info
 
+    | CXXNullPtrLiteralExpr(stmt_info, stmt_list, expr_info) ->
+        nullPtrExpr_trans trans_state stmt_info expr_info
+
     | ObjCSelectorExpr(stmt_info, stmt_list, expr_info, selector) ->
         objCSelectorExpr_trans trans_state stmt_info expr_info selector
 

infer/tests/codetoanalyze/cpp/frontend/literals/nullptr.cpp

@@ -0,0 +1 @@
+int* getPtr() {return nullptr;}

infer/tests/codetoanalyze/cpp/frontend/literals/nullptr.dot

@@ -0,0 +1,13 @@
+digraph iCFG {
+3 [label="3:  Return Stmt \n   *&return:int *=null [line 1]\n  APPLY_ABSTRACTION; [line 1]\n " shape="box"]
+	
+
+	 3 -> 2 ;
+2 [label="2: Exit getPtr \n  " color=yellow style=filled]
+	
+
+1 [label="1: Start getPtr\nFormals: \nLocals:  \n   DECLARE_LOCALS(&return); [line 1]\n " color=yellow style=filled]
+	
+
+	 1 -> 3 ;
+}

infer/tests/frontend/cpp/LiteralsTest.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2013- Facebook.
+ * All rights reserved.
+ */
+
+package frontend.cpp;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static utils.matchers.DotFilesEqual.dotFileEqualTo;
+
+import com.google.common.collect.ImmutableList;
+
+import org.junit.Rule;
+import org.junit.Test;
+
+import java.io.File;
+import java.io.IOException;
+
+import utils.DebuggableTemporaryFolder;
+import utils.InferException;
+import utils.InferRunner;
+
+public class LiteralsTest {
+
+  @Rule
+  public DebuggableTemporaryFolder folder = new DebuggableTemporaryFolder();
+
+  @Test
+  public void whenCaptureRunCommaThenDotFilesAreTheSame()
+      throws InterruptedException, IOException, InferException {
+    String literal_src =
+        "infer/tests/codetoanalyze/cpp/frontend/literals/nullptr.cpp";
+
+    String literal_dotty =
+        "infer/tests/codetoanalyze/cpp/frontend/literals/nullptr.dot";
+
+    ImmutableList<String> inferCmd =
+        InferRunner.createCPPInferCommandFrontend(
+            folder,
+            literal_src);
+    File newDotFile = InferRunner.runInferFrontend(inferCmd);
+    assertThat(
+        "In the capture of " + literal_src +
+            " the dotty files should be the same.",
+        newDotFile, dotFileEqualTo(literal_dotty));
+  }
+}

infer/tests/utils/InferRunner.java

@@ -166,6 +166,16 @@ public class InferRunner {
     return langOption;
   }
 
+  public static String getStdParam(Language lang) {
+    String stdParam = "";
+    switch (lang) {
+      case CPP:
+        stdParam = "-std=c++11";
+        break;
+    }
+    return stdParam;
+  }
+
   public static ImmutableList<String> createClangCommand(
     String sourceFile,
     Language lang,
@@ -188,6 +198,7 @@ public class InferRunner {
         .add("clang")
         .add("-x")
         .add(getClangLangOption(lang))
+        .add(getStdParam(lang))
         .addAll(isysrootOption.build())
         .addAll(arcOption.build())
         .add("-c")