va_list_ref

Overview

va_list_ref is a helper class to store a reference to a std::va_list starting with a call of macro va_start.

In C++98, there’s the lack of the std::va_copy macro and thus only references to std::va_list types can be used. Unfortunately the handling of these references is platform- specific. Therefore more than one implementation is provided and va_list_ref is a typedef.

std::va_list is a complete object type (in practice, a unique built-in type or char*) suitable for holding the information needed by the macros std::va_start (enables access), std::va_copy (makes a copy), std::va_arg (accesses the next argument), and std::va_end (ends traversal). These objects contains the pointer to the argument list which gets passed to variadic functions (functions that can take a variable number of arguments).

Example

This example shows how to create va_list_ref object as reference to variable :

    uint32_t t = 17U;
    estd::internal::_va_list_ref<uint32_t> cut(t);
    EXPECT_EQ(17U, cut.get());
    estd::internal::_va_list_ref<uint32_t> copy(cut);
    EXPECT_EQ(17U, copy.get());

This example shows how to create va_list_ref object as reference to array :

    using ArrayType = uint32_t[2];
    uint32_t t[2]   = {17U, 18U};
    estd::internal::_va_list_ref<ArrayType> cut(t);
    {
        ArrayType& value = cut.get();
        EXPECT_EQ(17U, value[0]);
        EXPECT_EQ(18U, value[1]);
    }
    estd::internal::_va_list_ref<ArrayType> copy(cut);
    {
        ArrayType& value = copy.get();
        EXPECT_EQ(17U, value[0]);
        EXPECT_EQ(18U, value[1]);
    }

This example shows how to create va_list_ref object to std::va_list as reference to std::va_list :

static char const* cptr = "a";

void testCopyConstructor(int start, ...)
{
    va_list ap;
    va_start(ap, start);
    estd::va_list_ref ref(ap);
    estd::va_list_ref cut(ref);
    ASSERT_EQ(cptr, va_arg(cut.get(), char const*));
    ASSERT_EQ(2U, va_arg(cut.get(), uint32_t));
    ASSERT_EQ(45345ULL, va_arg(cut.get(), uint64_t));
    va_end(ap);
}

    testCopyConstructor(1, cptr, 2, 45345ULL);