This commit adds an IsGenericValue meta function to match arbitrary
instantiations of the GenericValue template (or derived classes).
This meta function is used in the SFINAE-checks to avoid matching
the generic APIs (operator=,==,!=; AddMember, PushBack) for instances
of the main template. This avoids ambiguities with the GenericValue
overloads.
Several GenericValue functions take a const-reference to another GenericValue
only. These functions can safely accept values with a different allocator
type.
The following functions are therefore extended by a SourceAllocator template
parameter in this commit:
- operator==/!=/[]
- HasMember, FindMember, RemoveMember
- StringEqual
Before applying the simplifications in ed282b814, the SFINAE check for the
GenericValue(bool) constructor has been broken in MSVC 2005. Add a static
assert as a safe-guard against future reappearance of this problem.
As reported in #113, recent versions of Clang complain about
ambiguous overloads for some comparison operator instantiations,
especially if the deduced template type is a GenericValue.
Add an explicit, non-templated version for now (which is a better
match).
This only solves part of the problem, as comparisons between
* GenericValue & GenericDocument
* GenericValue with different SourceAllocator types
will still cause ambiguities.
Some users may want to use RapidJSON with std::string objects. This commits
adds an (opt-in) feature to include some basic support. The implementation
uses std::basic_string<Ch> as generic string type.
Support currently covers:
* construction
* comparison
No special APIs for AddMember or PushBack have been added, as std::string
most probably requires copying (or an explicit StringRef() call).
By restructuring the call forwarding of the various operator== and
operator!= overloads, new overloads can be added by simply adding an
additional member operator==.
Additionally, the "Ch*" overloads are dropped in favour of an SFINAE
version that removes the pointer variants from matching the templated
operator== (see also operator=).
It is not very useful for iterative parsing as the worst case of heap
size is O(n) where n is number of character in JSON, for the worst
synthetic cases. This is reasonable and should not create stack overflow
security problem as in recursive parsing.
While MSVC doesn't like the explicit `.template operator=<...>` syntax
(see 4f40ed6), Clang 3.5 complains about the absence of it:
In file included from ../../test/perftest/rapidjsontest.cpp:6:
../../include/rapidjson/document.h:504:18: error: use 'template' keyword to treat 'operator =' as a dependent template name
return (*this).operator=<StringRefType>(str);
^
template
Delegate both operator=(StringRefType) and operator=(T) to operator(GenericValue&).
The `StringRefType` assignment operator overload
leads to a compiler error on MSVC 2005 and later:
..\..\include\rapidjson/document.h(504) : error C2951: template declarations are only permitted at global, namespace, or class scope
Drop the unneeded 'template' keyword here.
