* re-introduce `std.build.Target` which is distinct from `std.Target`.
`std.build.Target` wraps `std.Target` so that it can be annotated as
"the native target" or an explicitly specified target.
* `std.Target.Os` is moved to `std.Target.Os.Tag`. The former is now a
struct which has the tag as well as version range information.
* `std.elf` gains some more ELF header constants.
* `std.Target.parse` gains the ability to parse operating system
version ranges as well as glibc version.
* Added `std.Target.isGnuLibC()`.
* self-hosted dynamic linker detection and glibc version detection.
This also adds the improved logic using `/usr/bin/env` rather than
invoking the system C compiler to find the dynamic linker when zig
is statically linked. Related: #2084
Note: this `/usr/bin/env` code is work-in-progress.
* `-target-glibc` CLI option is removed in favor of the new `-target`
syntax. Example: `-target x86_64-linux-gnu.2.27`
closes#1907
* Delete `std.net.TmpWinAddr`. I don't think that was ever meant to
be a real thing.
* Delete `std.net.OsAddress`. This abstraction was not helpful.
* Rename `std.net.Address` to `std.net.IpAddress`. It is now an extern
union of IPv4 and IPv6 addresses.
* Move `std.net.parseIp4` and `std.net.parseIp6` to the
`std.net.IpAddress` namespace. They now return `IpAddress` instead of
`u32` and `std.net.Ip6Addr`, which is deleted.
* Add `std.net.IpAddress.parse` which accepts a port and parses either
an IPv4 or IPv6 address.
* Add `std.net.IpAddress.parseExpectingFamily` which additionally
accepts a `family` parameter.
* `std.net.IpAddress.initIp4` and `std.net.IpAddress.initIp6` are
improved to directly take the address fields instead of a weird
in-between type.
* `std.net.IpAddress.port` is renamed to `std.net.IpAddress.getPort`.
* Added `std.net.IpAddress.setPort`.
* `os.sockaddr` struct on all targets is improved to match the
corresponding system struct. Previously I had made it a union of
sockaddr_in, sockaddr_in6, and sockaddr_un. The new abstraction for
this is now `std.net.IpAddress`.
* `os.sockaddr` and related bits are added for Windows.
* `os.sockaddr` and related bits now have the `zero` fields default
to zero initialization, and `len` fields default to the correct size.
This is enough to abstract the differences across targets, and so
no more switch on the target OS is needed in `std.net.IpAddress`.
* Add the missing `os.sockaddr_un` on FreeBSD and NetBSD.
* `std.net.IpAddress.initPosix` now takes a pointer to `os.sockaddr`.
* delete the std/event/net directory
* `std.event.Loop.waitUntilFdReadable` and related functions
no longer have possibility of failure. On Linux, they fall
back to poll() and then fall back to sleep().
* add some missing `noasync` decorations in `std.event.Loop`
* redo the `std.net.Server` API. it's quite nice now, but
shutdown does not work cleanly. There is a race condition with
close() that I am actively working on.
* move `std.io.OutStream` to its own file to match `std.io.InStream`.
I started working on making `write` integrated with evented I/O,
but it got tricky so I backed off and filed #3557. However
I did integrate `std.os.writev` and `std.os.pwritev` with evented I/O.
* add `std.Target.stack_align`
* move networking tests to `lib/std/net/test.zig`
* add `std.net.tcpConnectToHost` and `std.net.tcpConnectToAddress`.
* rename `error.UnknownName` to `error.UnknownHostName` within the
context of DNS resolution.
* add `std.os.readv`, which is integrated with evented I/O.
* `std.os.preadv`, is now integrated with evented I/O.
* `std.os.accept4` now asserts that ENOTSOCK and EOPNOTSUPP never
occur (misuse of API), instead of returning errors.
* `std.os.connect` is now integrated with evented I/O.
`std.os.connect_async` is gone. Just use `std.os.connect`.
* fix false positive dependency loop regarding async function frames
* add more compile notes to help when dependency loops occur
in determining whether a function is async.
* ir: change an assert to ir_assert to make it easier to find
workarounds for when such an assert is triggered. In this case
it was trying to parse an IPv4 address at comptime.
