Description
Hi! I transitively use socket2 as part of a Rust project built with
Bazel. I’m noting that socket2 builds successfully for me at v0.3.15,
but not at version v0.3.16 (released today) unless I specify the extra
flag --cfg=libc_align. I’m a bit hesitant to do so because it feels
low-level and platform specific, so I wanted to check and see whether
this is expected or whether there’s a better solution?
Here is a repro repo. You do need to have Bazel to repro, but you
don’t need any additional setup. The error is:
INFO: From Compiling Rust lib socket2 v0.3.16 (7 files):
error[E0063]: missing field `__align` in initializer of `libc::in6_addr`
--> external/raze__socket2__0_3_16/src/sockaddr.rs:243:25
|
243 | let sin6_addr = in6_addr {
| ^^^^^^^^ missing `__align`
error: aborting due to previous error
For more information about this error, try `rustc --explain E0063`.
ERROR: /HOMEDIR/.cache/bazel/_bazel_wchargin/e6b2d93af64d3456b38c9c9d2131e939/external/raze__socket2__0_3_16/BUILD.bazel:33:13: output 'external/raze__socket2__0_3_16/libsocket2--1560485693.rlib' was not created
ERROR: /HOMEDIR/.cache/bazel/_bazel_wchargin/e6b2d93af64d3456b38c9c9d2131e939/external/raze__socket2__0_3_16/BUILD.bazel:33:13: not all outputs were created or valid
Target @raze__socket2__0_3_16//:socket2 failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 0.707s, Critical Path: 0.20s
INFO: 2 processes: 1 internal, 1 linux-sandbox.
FAILED: Build did NOT complete successfully
I dug far enough into the libc structure to see the align/no_align
modules and guess that this cfg flag would probably fix it; it does.
The failing Bazel action, with directory structure and command line
invocation, is here (in a Gist because it has some long paths):
https://gist.github.com/wchargin/4da947cf43d2a241cfffb89873788a82
In all cases, the libc dependency is at version 0.2.80. But I note
that socket2 v0.3.15 depends on libc with default features, whereas
in v0.3.16 it depends on the align feature:
$ cargo tree -e features --manifest-path socket2-0.3.15/Cargo.toml
socket2-libc-align-demo v0.0.0 (/HOMEDIR/git/socket2-libc-align-demo/socket2-0.3.15)
└── socket2 feature "default"
└── socket2 v0.3.15
├── cfg-if feature "default"
│ └── cfg-if v0.1.10
└── libc feature "default"
├── libc v0.2.80
└── libc feature "std"
└── libc v0.2.80
$ cargo tree -e features --manifest-path socket2-0.3.16-default/Cargo.toml
socket2-libc-align-demo v0.0.0 (/HOMEDIR/git/socket2-libc-align-demo/socket2-0.3.16-default)
└── socket2 feature "default"
└── socket2 v0.3.16
├── cfg-if feature "default"
│ └── cfg-if v0.1.10
├── libc feature "align"
│ └── libc v0.2.80
└── libc feature "default"
├── libc v0.2.80
└── libc feature "std"
└── libc v0.2.80
$ cargo tree -e features --manifest-path socket2-0.3.16-libc-align/Cargo.toml
socket2-libc-align-demo v0.0.0 (/HOMEDIR/git/socket2-libc-align-demo/socket2-0.3.16-libc-align)
└── socket2 feature "default"
└── socket2 v0.3.16
├── cfg-if feature "default"
│ └── cfg-if v0.1.10
├── libc feature "align"
│ └── libc v0.2.80
└── libc feature "default"
├── libc v0.2.80
└── libc feature "std"
└── libc v0.2.80
So I’m hoping that you can help me understand what caused this change,
why it requires me to build with --cfg=libc_align, (maybe) why it’s
needed with Bazel but not with Cargo (though I understand if that’s
outside your purview/expertise), and whether I should feel comfortable
doing so? I want to build for non-Linux platforms, too, eventually.
I’m on rustc 1.47.0 (18bf6b4f0 2020-10-07) on Debian-like Linux.
Thanks much!