Check if CLING_RUNTIME_PRINT_VALUE_H defined before including RuntimePrintValue.h.

Author: marsupial

lib/Interpreter/ValuePrinter.cpp

@@ -869,13 +869,18 @@ namespace cling {
       // But user can undo past the transaction that invoked this, so whether
       // we are first or not is known by the interpreter.
       //
-      // Additionally add any transactions that occur in this scope as
-      // children to the transaction that invoked us
+      // When printing has already occured once or RuntimePrintValue.h was
+      // explicitly included, then Transaction merging has to occur here.
+      //
+      // Additionally the user could have included RuntimePrintValue.h before
+      // this code is run, so if there is no print transaction, check if
+      // CLING_RUNTIME_PRINT_VALUE_H is defined.
+      // FIXME: Relying on this macro isn't the best, but what's another way?
 
       Interpreter* Interp = V.getInterpreter();
       Interpreter::TransactionMerge M(Interp, true);
       const Transaction*& T = Interp->printValueTransaction();
-      if (!T) {
+      if (!T && !Interp->getMacro("CLING_RUNTIME_PRINT_VALUE_H")) {
         // DiagnosticErrorTrap Trap(Interp->getSema().getDiagnostics());
         Interp->declare("#include \"cling/Interpreter/RuntimePrintValue.h\"",
                         const_cast<Transaction**>(&T));

test/Prompt/ValuePrinter/ExplicitInclude.C

@@ -0,0 +1,28 @@
+//------------------------------------------------------------------------------
+// CLING - the C++ LLVM-based InterpreterG :)
+//
+// This file is dual-licensed: you can choose to license it under the University
+// of Illinois Open Source License or the GNU Lesser General Public License. See
+// LICENSE.TXT for details.
+
+//------------------------------------------------------------------------------
+
+// RUN: cat %s | %cling -Xclang -verify 2>&1 | FileCheck %s
+
+#include "cling/Interpreter/RuntimePrintValue.h"
+
+struct Trigger { } trgr
+// CHECK: (struct Trigger &) @0x{{.*}}
+.undo
+
+struct Trigger2 { } trgr
+// CHECK-NEXT: (struct Trigger2 &) @0x{{.*}}
+.undo
+
+.undo // #include "cling/Interpreter/RuntimePrintValue.h"
+
+struct Trigger3 { } trgr
+// CHECK-NEXT: (struct Trigger3 &) @0x{{.*}}
+
+// expected-no-diagnostics
+.q