Add dl_iterate_phdr to some BSD OSs

[tesuji]

Add dl_iterate_phdr for freebsd, openbsd and netbsd: #1066
cc rust-lang/backtrace-rs#325

[rust-highfive]

r? @JohnTitor

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[tesuji]

Done. CI should be green!

[semarie]

I just tested it on OpenBSD, and it failed due to `p_type` error. Adding a `cfg.skip_field` section as for freebsd makes the tests to pass on OpenBSD. Could you add it inside test_openbsd() ? Else I will correct it after your PR to be commited. Thanks to have provided the types and function on OpenBSD !

[semarie]

tests are fine on OpenBSD. thanks !

[tesuji]

Looks like it works: rust-lang/rust#78184 (comment).
Ping @JohnTitor @joshtriplett

[JohnTitor]

Looks good to me, thanks!
@bors r+

[bors]

📌 Commit 5c23d75 has been approved by JohnTitor

[bors]

⌛ Testing commit 5c23d75 with merge 199a516...

[bors]

💔 Test failed - checks-actions

[JohnTitor]

The failure is:

error: type alias is never used: `Elf_Addr`
  --> src/unix/bsd/netbsdlike/netbsd/mod.rs:34:9
   |
34 |         type Elf_Addr = Elf64_Addr;
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
note: the lint level is defined here
  --> src/lib.rs:18:38
   |
18 | #![cfg_attr(libc_deny_warnings, deny(warnings))]
   |                                      ^^^^^^^^
   = note: `#[deny(dead_code)]` implied by `#[deny(warnings)]`

error: type alias is never used: `Elf_Half`
  --> src/unix/bsd/netbsdlike/netbsd/mod.rs:35:9
   |
35 |         type Elf_Half = Elf64_Half;
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: type alias is never used: `Elf_Phdr`
  --> src/unix/bsd/netbsdlike/netbsd/mod.rs:36:9
   |
36 |         type Elf_Phdr = Elf64_Phdr;
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 3 previous errors

Ah, anyway we should "use" them here.

[tesuji]

I'm sorry. I made a mistake in netbsd code. The diff of change is 5c23d75...be37f01 .

[JohnTitor]

@bors r+

[bors]

📌 Commit be37f01 has been approved by JohnTitor

[bors]

⌛ Testing commit be37f01 with merge b1c314f...

[bors]

💔 Test failed - checks-actions

[tesuji]

What is this error? https://github.com/rust-lang/libc/runs/1314551399#step:5:1496

2020-10-27T12:32:07.6255772Z LLVM ERROR: unable to allocate function return #6
2020-10-27T12:32:07.6305138Z error: could not compile `compiler_builtins`

+ rustup target add sparc-unknown-linux-gnu
documenting sparc-unknown-linux-gnu
error: toolchain 'nightly-x86_64-unknown-linux-gnu' does not contain component 'rust-std' for target 'sparc-unknown-linux-gnu'; did you mean 'sparc64-unknown-linux-gnu'?
+ true
+ export RUSTDOCFLAGS=--cfg freebsd11
+ cargo doc --target sparc-unknown-linux-gnu --no-default-features --features extra_traits
   Compiling libc v0.2.80 (/home/runner/work/libc/libc)
 Documenting libc v0.2.80 (/home/runner/work/libc/libc)
error[E0463]: can't find crate for `core`
  |
  = note: the `sparc-unknown-linux-gnu` target may not be installed

error: aborting due to previous error

[JohnTitor]

The second error is unrelated, sparc-unknown-linux-gnu is no core target and we use the build-std feature in that case.
I think the first error is the cause, I recently updated compiler_builtins to 0.1.36 (rust-lang/rust#78209) and it seems that the bump causes the failure.

[JohnTitor]

@bors retry

[bors]

⌛ Testing commit be37f01 with merge 58a9de3...

[JohnTitor]

@bors retry
Encountered the spurious failure on rollup :(

[bors]

⌛ Testing commit be37f01 with merge ebefd7b...

[tesuji]

Can we create a new patch release for this PR ?