Assert when outputting JSON using PrettyWriter

[sjasonsmith]

Using PrettyWriter to output JSON I encounter an assert when PutN is used to indent the output.

I hit the same assert with both Visual C++ 2008 and GCC 4.7.

Assertion failed: stackTop_ + sizeof(T) * count <= stackEnd_, file d:\p4\thirdpartyexports\rapidjson\export\1.0\1.0.3a2\includes\rapidjson\internal/stack.h, line 129

It appears to be an issue in PutN in stream.h. It instantiates templates differently for PutReserve and PutUnsafe. This causes it to use use PutReserve from stream.h (which does nothing), then uses PutUnsafe from stringbuffer.h (which assumes PutReserve allocated space).

Contents of stream.h PutN which causes assertion:

   //! Put N copies of a character to a stream.
   template<typename Stream, typename Ch>
   inline void PutN(Stream& stream, Ch c, size_t n) {
       PutReserve<Stream>(stream, n);
       for (size_t i = 0; i < n; i++)
           PutUnsafe(stream, c);
   }

Removing the template argument from PutReserve seems to resolve the issue, as it now uses PutReserve from stringbuffer.h.

Revised stream.h PutN which does not cause assertion:

   //! Put N copies of a character to a stream.
   template<typename Stream, typename Ch>
   inline void PutN(Stream& stream, Ch c, size_t n) {
       PutReserve(stream, n);
       for (size_t i = 0; i < n; i++)
           PutUnsafe(stream, c);
   }

[sjasonsmith]

It looks like I triggered this by using GenericStringBuffer<UTF8<>, MemoryPoolAllocator<> >. When used with a non-default allocator, PutN doesn't match the template specialization in stringbuffer.h, and falls back to the generic implementation in stream.h.

I am verifying my own fix for this, and will put up a pull request to add a failing test and fix the issue.