Storage Type Narrowing
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#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
template<size_t N>
struct Storage {
uint8_t storage[N];
};
template<typename T> inline
Storage<sizeof(T)> storage_convert(T value) {
Storage<sizeof(T)> result;
memmove(&result.storage, &value, sizeof(T));
return result;
}
template<typename T> inline
T storage_cast(Storage<sizeof(T)> value) {
T result;
memmove(&result, &value.storage, sizeof(T));
return result;
}
template<size_t N>
void list_add(Storage<N> s) {
printf("impl: %p\n", &list_add<N>);
}
template<typename T>
struct List {
inline
void add(T v) {
list_add(storage_convert(v));
}
};
int main() {
List<int32_t> a = {};
List<uint32_t> b = {};
List<uint64_t> c = {};
a.add(32);
b.add(51);
c.add(72);
auto d = storage_convert(2);
// You can miscast the type if it's the same size
auto e = storage_cast<uint32_t>(d);
// This is a compile error because it's a different size.
//auto f = storage_cast<uint64_t>(d);
return 0;
}
Cpp
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