解析公共派生基类模板中功能模板的名称的“未在此范围内声明”错误

考虑（link）：

#include <cstdlib>
#include <cassert>

#pragma pack (1)

template <size_t Width>
class Base
{
public:
    char mData [Width];
    template <typename Field> Field ExtractAs () const
    {
        return *reinterpret_cast <Field> (mData);
    }
};

template <typename FieldVal>
class IntegralField
:
    public Base <sizeof (FieldVal)>
{
public:
    FieldVal GetVal () const
    {
        return ExtractAs <FieldVal> ();
    }
};

int main()
{
    char raw[4] = {0x11, 0x22, 0x33, 0x44};
    typedef IntegralField <uint32_t> UInt32Field;
    const UInt32Field& field =
        *reinterpret_cast <const UInt32Field*> (raw);
    const uint32_t extracted = field.GetVal();
    assert (extracted == 0x44332211);
}

电话：

return ExtractAs <FieldVal> ();

无法在g ++ 4.7.2下使用以下命令进行编译：

main.cpp: In member function ‘FieldVal IntegralField<FieldVal>::GetVal() const’:
main.cpp:25:16: error: ‘ExtractAs’ was not declared in this scope
main.cpp:25:35: error: expected primary-expression before ‘>’ token
main.cpp:25:38: error: expected primary-expression before ‘)’ token
main.cpp: In function ‘int main()’:
main.cpp:32:28: error: ‘uint32_t’ was not declared in this scope
main.cpp:32:36: error: template argument 1 is invalid
main.cpp:32:49: error: invalid type in declaration before ‘;’ token
main.cpp:35:11: error: ‘uint32_t’ does not name a type
main.cpp:36:5: error: ‘extracted’ was not declared in this scope
ninja: build stopped: subcommand failed.

我尝试了许多技巧，包括using Base::ExtractAs，typedefs等，但都无济于事。

我想在C ++ 03中做些什么吗？如何从派生类模板成员函数调用基类模板中的函数模板？请注意，我不能使用C ++ 11。

编辑：当我重新定义GetVal更明确的类型时：

  FieldVal GetVal () const
    {
        static const size_t fieldSize = sizeof (FieldVal);
        typedef Base <fieldSize> MyBase;
        typedef FieldVal MyField;
        return MyBase::ExtractAs <MyField> ();
    }

我仍然得到：

error: expected primary-expression before ‘>’ token

在： return MyBase::ExtractAs <MyField> ();

编辑：这是最终的工作代码：

#include <cstdlib>
#include <cassert>
#include <stdint.h>

#pragma pack (1)

template <size_t Width>
class Base
{
public:
    char mData [Width];
    template <typename Field> Field ExtractAs () const
    {
        return *reinterpret_cast <const Field*> (mData);
    }
};

template <typename FieldVal>
class IntegralField
:
    public Base <sizeof (FieldVal)>
{
public:
    FieldVal GetVal () const
    {
        return this->template ExtractAs<FieldVal>();
    }
};

int main()
{
    char raw[4] = {0x11, 0x22, 0x33, 0x44};
    typedef IntegralField <uint32_t> UInt32Field;
    const UInt32Field& field =
        *reinterpret_cast <const UInt32Field*> (raw);
    const uint32_t extracted = field.GetVal();
    assert (extracted == 0x44332211);
}