win: Resolve zero-length array errors on MSVC

In some cases, it's sufficient to move the zero-length array to the end of the
structure. When the struct is used inside a class that is derived from however,
this fails. In that case, switch to holding the object in a scoped_ptr.

Longer winded version: https://groups.google.com/a/chromium.org/d/msg/crashpad-dev/NGZ6LwRMORM/nKcXKQ7inIEJ

R=mark@chromium.org
BUG=crashpad:1

Review URL: https://codereview.chromium.org/896663006

minidump/minidump_extensions.h

@@ -24,6 +24,16 @@
 #include "build/build_config.h"
 #include "util/misc/uuid.h"
 
+#if defined(COMPILER_MSVC)
+// C4200 is "nonstandard extension used : zero-sized array in struct/union".
+// We would like to globally disable this warning, but unfortunately, the
+// compiler is buggy and only supports disabling it with a pragma, so we can't
+// disable it with other silly warnings in build/common.gypi. See:
+//   https://connect.microsoft.com/VisualStudio/feedback/details/1114440
+#pragma warning(push)
+#pragma warning(disable: 4200)
+#endif  // COMPILER_MSVC
+
 #if defined(COMPILER_MSVC)
 #define PACKED
 #pragma pack(push, 1)
@@ -460,6 +470,10 @@ struct ALIGNAS(4) PACKED MinidumpCrashpadInfo {
 #endif  // COMPILER_MSVC
 #undef PACKED
 
+#if defined(COMPILER_MSVC)
+#pragma warning(pop)  // C4200
+#endif  // COMPILER_MSVC
+
 }  // namespace crashpad
 
 #endif  // CRASHPAD_MINIDUMP_MINIDUMP_EXTENSIONS_H_

minidump/minidump_location_descriptor_list_writer.cc

@@ -23,7 +23,7 @@ namespace internal {
 
 MinidumpLocationDescriptorListWriter::MinidumpLocationDescriptorListWriter()
     : MinidumpWritable(),
-      location_descriptor_list_base_(),
+      location_descriptor_list_base_(new MinidumpLocationDescriptorList()),
       children_(),
       child_location_descriptors_() {
 }
@@ -47,7 +47,8 @@ bool MinidumpLocationDescriptorListWriter::Freeze() {
   }
 
   size_t child_count = children_.size();
-  if (!AssignIfInRange(&location_descriptor_list_base_.count, child_count)) {
+  if (!AssignIfInRange(&location_descriptor_list_base_->count,
+                       child_count)) {
     LOG(ERROR) << "child_count " << child_count << " out of range";
     return false;
   }
@@ -64,7 +65,7 @@ bool MinidumpLocationDescriptorListWriter::Freeze() {
 size_t MinidumpLocationDescriptorListWriter::SizeOfObject() {
   DCHECK_GE(state(), kStateFrozen);
 
-  return sizeof(location_descriptor_list_base_) +
+  return sizeof(*location_descriptor_list_base_) +
          children_.size() * sizeof(MINIDUMP_LOCATION_DESCRIPTOR);
 }
 
@@ -86,8 +87,8 @@ bool MinidumpLocationDescriptorListWriter::WriteObject(
   DCHECK_EQ(children_.size(), child_location_descriptors_.size());
 
   WritableIoVec iov;
-  iov.iov_base = &location_descriptor_list_base_;
-  iov.iov_len = sizeof(location_descriptor_list_base_);
+  iov.iov_base = location_descriptor_list_base_.get();
+  iov.iov_len = sizeof(*location_descriptor_list_base_);
   std::vector<WritableIoVec> iovecs(1, iov);
 
   if (!child_location_descriptors_.empty()) {

minidump/minidump_location_descriptor_list_writer.h

@@ -70,7 +70,7 @@ class MinidumpLocationDescriptorListWriter : public MinidumpWritable {
   bool WriteObject(FileWriterInterface* file_writer) override;
 
  private:
-  MinidumpLocationDescriptorList location_descriptor_list_base_;
+  scoped_ptr<MinidumpLocationDescriptorList> location_descriptor_list_base_;
   PointerVector<MinidumpWritable> children_;
   std::vector<MINIDUMP_LOCATION_DESCRIPTOR> child_location_descriptors_;
 

minidump/minidump_memory_writer.cc

@@ -162,9 +162,9 @@ internal::MinidumpWritable::Phase MinidumpMemoryWriter::WritePhase() {
 
 MinidumpMemoryListWriter::MinidumpMemoryListWriter()
     : MinidumpStreamWriter(),
-      memory_list_base_(),
       memory_writers_(),
-      children_() {
+      children_(),
+      memory_list_base_() {
 }
 
 MinidumpMemoryListWriter::~MinidumpMemoryListWriter() {

minidump/minidump_memory_writer.h

@@ -180,9 +180,9 @@ class MinidumpMemoryListWriter final : public internal::MinidumpStreamWriter {
   MinidumpStreamType StreamType() const override;
 
  private:
-  MINIDUMP_MEMORY_LIST memory_list_base_;
   std::vector<MinidumpMemoryWriter*> memory_writers_;  // weak
   PointerVector<MinidumpMemoryWriter> children_;
+  MINIDUMP_MEMORY_LIST memory_list_base_;
 
   DISALLOW_COPY_AND_ASSIGN(MinidumpMemoryListWriter);
 };

minidump/minidump_module_writer.cc

@@ -375,7 +375,7 @@ bool MinidumpModuleWriter::WriteObject(FileWriterInterface* file_writer) {
 }
 
 MinidumpModuleListWriter::MinidumpModuleListWriter()
-    : MinidumpStreamWriter(), module_list_base_(), modules_() {
+    : MinidumpStreamWriter(), modules_(), module_list_base_() {
 }
 
 MinidumpModuleListWriter::~MinidumpModuleListWriter() {

minidump/minidump_module_writer.h

@@ -346,8 +346,8 @@ class MinidumpModuleListWriter final : public internal::MinidumpStreamWriter {
   MinidumpStreamType StreamType() const override;
 
  private:
-  MINIDUMP_MODULE_LIST module_list_base_;
   PointerVector<MinidumpModuleWriter> modules_;
+  MINIDUMP_MODULE_LIST module_list_base_;
 
   DISALLOW_COPY_AND_ASSIGN(MinidumpModuleListWriter);
 };

minidump/minidump_rva_list_writer.cc

@@ -23,7 +23,7 @@ namespace internal {
 
 MinidumpRVAListWriter::MinidumpRVAListWriter()
     : MinidumpWritable(),
-      rva_list_base_(),
+      rva_list_base_(new MinidumpRVAList()),
       children_(),
       child_rvas_() {
 }
@@ -46,7 +46,7 @@ bool MinidumpRVAListWriter::Freeze() {
   }
 
   size_t child_count = children_.size();
-  if (!AssignIfInRange(&rva_list_base_.count, child_count)) {
+  if (!AssignIfInRange(&rva_list_base_->count, child_count)) {
     LOG(ERROR) << "child_count " << child_count << " out of range";
     return false;
   }
@@ -62,7 +62,7 @@ bool MinidumpRVAListWriter::Freeze() {
 size_t MinidumpRVAListWriter::SizeOfObject() {
   DCHECK_GE(state(), kStateFrozen);
 
-  return sizeof(rva_list_base_) + children_.size() * sizeof(RVA);
+  return sizeof(*rva_list_base_) + children_.size() * sizeof(RVA);
 }
 
 std::vector<MinidumpWritable*> MinidumpRVAListWriter::Children() {
@@ -81,8 +81,8 @@ bool MinidumpRVAListWriter::WriteObject(FileWriterInterface* file_writer) {
   DCHECK_EQ(children_.size(), child_rvas_.size());
 
   WritableIoVec iov;
-  iov.iov_base = &rva_list_base_;
-  iov.iov_len = sizeof(rva_list_base_);
+  iov.iov_base = rva_list_base_.get();
+  iov.iov_len = sizeof(*rva_list_base_);
   std::vector<WritableIoVec> iovecs(1, iov);
 
   if (!child_rvas_.empty()) {

minidump/minidump_rva_list_writer.h

@@ -66,7 +66,7 @@ class MinidumpRVAListWriter : public MinidumpWritable {
   bool WriteObject(FileWriterInterface* file_writer) override;
 
  private:
-  MinidumpRVAList rva_list_base_;
+  scoped_ptr<MinidumpRVAList> rva_list_base_;
   PointerVector<MinidumpWritable> children_;
   std::vector<RVA> child_rvas_;
 

minidump/minidump_simple_string_dictionary_writer.cc

@@ -91,7 +91,7 @@ bool MinidumpSimpleStringDictionaryEntryWriter::WriteObject(
 }
 
 MinidumpSimpleStringDictionaryWriter::MinidumpSimpleStringDictionaryWriter()
-    : MinidumpWritable(), simple_string_dictionary_base_(), entries_() {
+    : MinidumpWritable(), entries_(), simple_string_dictionary_base_() {
 }
 
 MinidumpSimpleStringDictionaryWriter::~MinidumpSimpleStringDictionaryWriter() {

minidump/minidump_simple_string_dictionary_writer.h

@@ -132,11 +132,11 @@ class MinidumpSimpleStringDictionaryWriter final
   bool WriteObject(FileWriterInterface* file_writer) override;
 
  private:
-  MinidumpSimpleStringDictionary simple_string_dictionary_base_;
-
   // This object owns the MinidumpSimpleStringDictionaryEntryWriter objects.
   std::map<std::string, MinidumpSimpleStringDictionaryEntryWriter*> entries_;
 
+  MinidumpSimpleStringDictionary simple_string_dictionary_base_;
+
   DISALLOW_COPY_AND_ASSIGN(MinidumpSimpleStringDictionaryWriter);
 };
 

minidump/minidump_string_writer.cc

@@ -26,7 +26,7 @@ namespace internal {
 
 template <typename Traits>
 MinidumpStringWriter<Traits>::MinidumpStringWriter()
-    : MinidumpWritable(), string_base_(), string_() {
+    : MinidumpWritable(), string_base_(new MinidumpStringType()), string_() {
 }
 
 template <typename Traits>
@@ -42,7 +42,7 @@ bool MinidumpStringWriter<Traits>::Freeze() {
   }
 
   size_t string_bytes = string_.size() * sizeof(string_[0]);
-  if (!AssignIfInRange(&string_base_.Length, string_bytes)) {
+  if (!AssignIfInRange(&string_base_->Length, string_bytes)) {
     LOG(ERROR) << "string_bytes " << string_bytes << " out of range";
     return false;
   }
@@ -55,7 +55,7 @@ size_t MinidumpStringWriter<Traits>::SizeOfObject() {
   DCHECK_GE(state(), kStateFrozen);
 
   // Include the NUL terminator.
-  return sizeof(string_base_) + (string_.size() + 1) * sizeof(string_[0]);
+  return sizeof(*string_base_) + (string_.size() + 1) * sizeof(string_[0]);
 }
 
 template <typename Traits>
@@ -66,8 +66,8 @@ bool MinidumpStringWriter<Traits>::WriteObject(
   // The string’s length is stored in string_base_, and its data is stored in
   // string_. Write them both.
   WritableIoVec iov;
-  iov.iov_base = &string_base_;
-  iov.iov_len = sizeof(string_base_);
+  iov.iov_base = string_base_.get();
+  iov.iov_len = sizeof(*string_base_);
   std::vector<WritableIoVec> iovecs(1, iov);
 
   // Include the NUL terminator.

minidump/minidump_string_writer.h

@@ -22,6 +22,7 @@
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/strings/string16.h"
 #include "minidump/minidump_extensions.h"
 #include "minidump/minidump_rva_list_writer.h"
@@ -75,7 +76,7 @@ class MinidumpStringWriter : public MinidumpWritable {
   const StringType& string() const { return string_; }
 
  private:
-  MinidumpStringType string_base_;
+  scoped_ptr<MinidumpStringType> string_base_;
   StringType string_;
 
   DISALLOW_COPY_AND_ASSIGN(MinidumpStringWriter);

minidump/minidump_thread_writer.cc

@@ -129,9 +129,9 @@ bool MinidumpThreadWriter::WriteObject(FileWriterInterface* file_writer) {
 
 MinidumpThreadListWriter::MinidumpThreadListWriter()
     : MinidumpStreamWriter(),
-      thread_list_base_(),
       threads_(),
-      memory_list_writer_(nullptr) {
+      memory_list_writer_(nullptr),
+      thread_list_base_() {
 }
 
 MinidumpThreadListWriter::~MinidumpThreadListWriter() {

minidump/minidump_thread_writer.h

@@ -202,9 +202,9 @@ class MinidumpThreadListWriter final : public internal::MinidumpStreamWriter {
   MinidumpStreamType StreamType() const override;
 
  private:
-  MINIDUMP_THREAD_LIST thread_list_base_;
   PointerVector<MinidumpThreadWriter> threads_;
   MinidumpMemoryListWriter* memory_list_writer_;  // weak
+  MINIDUMP_THREAD_LIST thread_list_base_;
 
   DISALLOW_COPY_AND_ASSIGN(MinidumpThreadListWriter);
 };