IcuErrorCode: Define virtual destructor in .cpp file

This fixes compiler warnings from clang:

src/training/icuerrorcode.h:44:7: warning:
 'IcuErrorCode' has no out-of-line virtual method definitions;
 its vtable will be emitted in every translation unit [-Wweak-vtables]

Signed-off-by: Stefan Weil <sw@weilnetz.de>

src/training/CMakeLists.txt

@@ -173,6 +173,7 @@ endif()
 ########################################
 
 set(unicharset_training_src
+    icuerrorcode.cpp
     icuerrorcode.h
     lang_model_helpers.cpp
     lang_model_helpers.h

src/training/Makefile.am

@@ -65,6 +65,7 @@ libtesseract_training_la_SOURCES = \
     commandlineflags.cpp \
     commontraining.cpp \
     degradeimage.cpp \
+    icuerrorcode.cpp \
     lang_model_helpers.cpp \
     ligature_table.cpp \
     lstmtester.cpp \

src/training/icuerrorcode.cpp

@@ -0,0 +1,28 @@
+///////////////////////////////////////////////////////////////////////
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+///////////////////////////////////////////////////////////////////////
+
+#include "icuerrorcode.h"
+
+namespace tesseract {
+
+// Destructor.
+// It is defined here, so the compiler can create a single vtable
+// instead of weak vtables in every compilation unit.
+IcuErrorCode::~IcuErrorCode() {
+  if (isFailure()) {
+    handleFailure();
+  }
+}
+
+}  // namespace tesseract.

src/training/icuerrorcode.h

@@ -7,7 +7,7 @@
  *
  * Features:
  * - The constructor initializes the internal UErrorCode to U_ZERO_ERROR,
- *  removing one common source of errors.
+ *   removing one common source of errors.
  * - Same use in C APIs taking a UErrorCode* (pointer) and C++ taking
  *   UErrorCode& (reference), via conversion operators.
  * - Automatic checking for success when it goes out of scope. On failure,
@@ -44,11 +44,7 @@ namespace tesseract {
 class IcuErrorCode : public icu::ErrorCode {
  public:
   IcuErrorCode() {}
-  virtual ~IcuErrorCode() {
-    if (isFailure()) {
-      handleFailure();
-    }
-  }
+  virtual ~IcuErrorCode();
 
  protected:
   virtual void handleFailure() const {