Change {Source,Binary}ErrorHandler to C++ (#403)

Added some new classes:

* BinaryErrorHandler: abstract base class
* BinaryErrorHandlerFile: writes errors to a FILE*
* SourceErrorHandler: abstract base class
* SourceErrorHandlerNop: eats all errors
* SourceErrorHandlerFile: writes errors to a FILE*

There are some specific ones as well:

* BinaryErrorHandlerAssert: used in wasm-interp to handle writing out a
  custom header with assertion "failures"; i.e. places where the error
  handler should fire.
* BinaryErrorHandlerModule: used when parsing a .wast, but there's an
  embedded binary file.

1 files changed, 59 insertions, 0 deletions

diff --git a/src/binary-error-handler.cc b/src/binary-error-handler.cc
new file mode 100644
index 00000000..c785d2af
--- /dev/null
+++ b/src/binary-error-handler.cc
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2017 WebAssembly Community Group participants
+ *
+ * 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 "binary-error-handler.h"
+
+#include "common.h"
+
+namespace wabt {
+
+BinaryErrorHandlerFile::BinaryErrorHandlerFile(FILE* file,
+                                               const std::string& header,
+                                               PrintHeader print_header)
+    : file_(file), header_(header), print_header_(print_header) {}
+
+bool BinaryErrorHandlerFile::OnError(uint32_t offset,
+                                     const std::string& error) {
+  PrintErrorHeader();
+  if (offset == WABT_UNKNOWN_OFFSET)
+    fprintf(file_, "error: %s\n", error.c_str());
+  else
+    fprintf(file_, "error: @0x%08x: %s\n", offset, error.c_str());
+  fflush(file_);
+  return true;
+}
+
+void BinaryErrorHandlerFile::PrintErrorHeader() {
+  if (header_.empty())
+    return;
+
+  switch (print_header_) {
+    case PrintHeader::Never:
+      break;
+
+    case PrintHeader::Once:
+      print_header_ = PrintHeader::Never;
+    // Fallthrough.
+
+    case PrintHeader::Always:
+      fprintf(file_, "%s:\n", header_.c_str());
+      break;
+  }
+  // If there's a header, indent the following message.
+  fprintf(file_, "  ");
+}
+
+}  // namespace wabt