If I create a static const std::map, it will allocate memory on heap. Following code throws bad_alloc:
#include <iostream>
#include <map>
class A {
public:
static const std::map<int, int> a;
};
const std::map<int, int> A::a = { { 1, 3} , { 2, 5} };
void* operator new ( std::size_t count )
{
throw std::bad_alloc();
}
int
main (void)
{
for(auto &ai: A::a) {
std::cout << ai.first << " " << ai.second << "\n";
}
return 0;
}
Is it possible to create this constant map somehow without having memory allocation?
As Igor Tandetnik suggested, a custom allocator would do the trick. The following is a quick'n'dirty example of a simple linear allocator, which returns memory slots from a static buffer:
Output:
Note that this allocator will only handle requests for single slots at a time. I'm sure you will figure out how to extend it according to your requirements.