Previously, pointer casting was used, but this resulted in strict-aliasing warnings:
IPAddress.h: In member function ‘IPAddress::operator uint32_t() const’:
IPAddress.h:46:61: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
operator uint32_t() const { return *((uint32_t*)_address); };
^
IPAddress.h: In member function ‘bool IPAddress::operator==(const IPAddress&) const’:
IPAddress.h:47:81: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
bool operator==(const IPAddress& addr) const { return (*((uint32_t*)_address)) == (*((uint32_t*)addr._address)); };
^
IPAddress.h:47:114: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
bool operator==(const IPAddress& addr) const { return (*((uint32_t*)_address)) == (*((uint32_t*)addr._address)); };
Converting between unrelated types like this is commonly done using a union,
which do not break the strict-aliasing rules. Using that union, inside
IPAddress there is now an attribute _address.bytes for the raw byte
arra, or _address.dword for the uint32_t version.
Since we now have easy access to the uint32_t version, this also removes
two memcpy invocations that can just become assignments.
This patch does not change the generated code in any way, the compiler
already optimized away the memcpy calls and the previous casts mean
exactly the same.
This is a different implementation of a part of #1399 and it helps
toward fixing #1728.
These functions do not modify the IPAddress object, but were not marked
as const. This meant that you could not do:
void set_ip(const IPAddress& ip) {
uint32_t copy = ip;
}
Since calling operator uint32_t() on ip would discard the constness of
the reference.
Cristian Maglie
Matthijs Kooijman
Cristian Maglie
amcewen