Silence "go build" warnings

[nenad]

Running go build results in the following message:

$ go build
# github.com/anacrolix/go-libutp
In file included from utp_api.cpp:26:
utp_internal.h: In constructor ‘UTPSocketKey::UTPSocketKey(const PackedSockAddr&, uint32)’:
utp_internal.h:79:32: warning: ‘void* memset(void*, int, size_t)’ clearing an object of non-trivial type ‘struct UTPSocketKey’; use assignment instead [-Wclass-memaccess]
   79 |   memset(this, 0, sizeof(*this));
      |                                ^
utp_internal.h:74:8: note: ‘struct UTPSocketKey’ declared here
   74 | struct UTPSocketKey {
      |        ^~~~~~~~~~~~
# github.com/anacrolix/go-libutp
In file included from utp_callbacks.h:27,
                 from utp_callbacks.cpp:25:
utp_internal.h: In constructor ‘UTPSocketKey::UTPSocketKey(const PackedSockAddr&, uint32)’:
utp_internal.h:79:32: warning: ‘void* memset(void*, int, size_t)’ clearing an object of non-trivial type ‘struct UTPSocketKey’; use assignment instead [-Wclass-memaccess]
   79 |   memset(this, 0, sizeof(*this));
      |                                ^
utp_internal.h:74:8: note: ‘struct UTPSocketKey’ declared here
   74 | struct UTPSocketKey {
      |        ^~~~~~~~~~~~
# github.com/anacrolix/go-libutp
In file included from utp_internal.cpp:34:
utp_internal.h: In constructor ‘UTPSocketKey::UTPSocketKey(const PackedSockAddr&, uint32)’:
utp_internal.h:79:32: warning: ‘void* memset(void*, int, size_t)’ clearing an object of non-trivial type ‘struct UTPSocketKey’; use assignment instead [-Wclass-memaccess]
   79 |   memset(this, 0, sizeof(*this));
      |                                ^
utp_internal.h:74:8: note: ‘struct UTPSocketKey’ declared here
   74 | struct UTPSocketKey {
      |        ^~~~~~~~~~~~

Go version:

$ go version
go version go1.12.7 linux/amd64

I found the solution from intel's TBB repository: oneapi-src/oneTBB#54
Seems it's safe to just cast to void*.

[nenad]

@anacrolix Please review when you have the time.

[anacrolix]

Maybe it would be better to push something upstream for this, or alter the C++ compilation flags?

[nenad]

Just submitted this PR to upstream: bittorrent/libutp#121

I played with the build flags, but I couldn't get rid of the warning 🤷‍♂️

Should I close this PR?

[anacrolix]

Leave it open. The warnings aren't desirable, so we can track fixing them here.

[anacrolix]

Thanks for your effort on this @nenad . If we can't get any movement upstream, I'll try it out here.

[anacrolix]

I got impatient with upstream, and was able to reproduce the warnings while cross compiling for a project. Thanks for your patience @nenad .