Repository: rust
Issue: std::net::TcpStream::connect() and .to_socket_addrs() segfault when address is "localhost:8080", build is static and /etc/hosts is empty on arch linux.
Labels: A-linkage,C-bug,O-linux-gnu

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Both of those function will segfault when trying to resolve localhost on any port if the following condition are met :
- the build is static (compiled with `rustc -C target-feature=+crt-static main.rs`
- the address used is "localhost:<any port>"
- the os is Arch Linux lattest (may work on other distros/OS)
- the file /etc/hosts is empty

I tried this code:

```rust
use std::net::ToSocketAddrs;

pub fn main() {
    println!("before");
    let _ = "localhost:8080".to_socket_addrs(); // will segfault
    std::net::TcpStream::connect("localhost:8080").unwrap(); // will also segfault
    println!("hello world");
}
```

I expected to see this happen: the address is resolved

Instead, this happened: the program segfault

<!--
If you're using the stable version of the compiler, you should also check if the
bug also exists in the beta or nightly versions.
-->

`rustc --version --verbose`:
```
rustc 1.65.0-nightly (9c20b2a8c 2022-08-17)
binary: rustc
commit-hash: 9c20b2a8cc7588decb6de25ac6a7912dcef24d65
commit-date: 2022-08-17
host: x86_64-unknown-linux-gnu
release: 1.65.0-nightly
LLVM version: 15.0.0
```
`uname -a`:  (This is Arch-linux lattest, i could not reproduce the bug on another distro, but still, it shouldn't segfault)
```
Linux Alkeryn-PC 5.19.1-arch2-1 #1 SMP PREEMPT_DYNAMIC Thu, 11 Aug 2022 16:06:13 +0000 x86_64 GNU/Linux
```
<!--
Include a backtrace in the code block by setting `RUST_BACKTRACE=1` in your
environment. E.g. `RUST_BACKTRACE=1 cargo build`.
-->
For the backtrace, RUST_BACKTRACE=1 did not work and gave the following output :
```
RUST_BACKTRACE=1 ./main
before
zsh: segmentation fault (core dumped)  RUST_BACKTRACE=1 ./main
```
so here is a backtrace made with gdb (don't mind the gef plugin being installed

<details><summary>Backtrace</summary>
<p>

```
[ Legend: Modified register | Code | Heap | Stack | String ]
──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── registers ────
$rax   : 0x0               
$rbx   : 0x3               
$rcx   : 0x007ffff7cf838e  →  0x310b77fffff0003d ("="?)
$rdx   : 0x007ffff7ff8490  →  <_dl_static_dtv+16> add BYTE PTR [rax], al
$rsp   : 0x007fffffffcaf0  →  "/proc/sys/net/ipv6/conf/all/disable_ipv6"
$rbp   : 0x007fffffffcc20  →  0x007fffffffcce0  →  0x0000000000000010
$rsi   : 0x007ffff7d99dd5  →  0x6225206125000200
$rdi   : 0x007ffff79c1c88  →  0x0000000000000005
$rip   : 0x007ffff79a5196  →   mov r12, QWORD PTR [rax+0x8]
$r8    : 0x0               
$r9    : 0x0               
$r10   : 0x1000            
$r11   : 0x206             
$r12   : 0x0               
$r13   : 0x007fffffffcaf0  →  "/proc/sys/net/ipv6/conf/all/disable_ipv6"
$r14   : 0x007fffffffccf0  →  0x0000000000000000
$r15   : 0x007fffffffcca0  →  0xe1efbb33d283a048
$eflags: [ZERO carry PARITY adjust sign trap INTERRUPT direction overflow RESUME virtualx86 identification]
$cs: 0x33 $ss: 0x2b $ds: 0x00 $es: 0x00 $fs: 0x00 $gs: 0x00 
──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── stack ────
0x007fffffffcaf0│+0x0000: "/proc/sys/net/ipv6/conf/all/disable_ipv6"	 ← $rsp, $r13
0x007fffffffcaf8│+0x0008: "s/net/ipv6/conf/all/disable_ipv6"
0x007fffffffcb00│+0x0010: "v6/conf/all/disable_ipv6"
0x007fffffffcb08│+0x0018: "all/disable_ipv6"
0x007fffffffcb10│+0x0020: "ble_ipv6"
0x007fffffffcb18│+0x0028: 0xffffffffffffff00
0x007fffffffcb20│+0x0030: 0x0000000000000000
0x007fffffffcb28│+0x0038: 0x007ffff79a4e33  →   lea rdx, [rax+0xb]
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── code:x86:64 ────
   0x7ffff79a5187                  je     0x7ffff79a51d0
   0x7ffff79a5189                  lea    rdi, [rip+0x1caf8]        # 0x7ffff79c1c88
   0x7ffff79a5190                  call   QWORD PTR [rip+0x1cc82]        # 0x7ffff79c1e18
 → 0x7ffff79a5196                  mov    r12, QWORD PTR [rax+0x8]
   0x7ffff79a519d                  mov    r13, rax
   0x7ffff79a51a0                  test   r12, r12
   0x7ffff79a51a3                  je     0x7ffff79a51e5
   0x7ffff79a51a5                  sub    r12, 0x1
   0x7ffff79a51a9                  mov    eax, 0x3ffffe
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── threads ────
[#0] Id 1, Name: "main", stopped 0x7ffff79a5196 in ?? (), reason: SIGSEGV
──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── trace ────
[#0] 0x7ffff79a5196 → mov r12, QWORD PTR [rax+0x8]
[#1] 0x7ffff79ad6b1 → jmp 0x7ffff79ad518
[#2] 0x7ffff79a1045 → mov rbx, QWORD PTR [rsp]
[#3] 0x7ffff79aa1a6 → _nss_myhostname_gethostbyname4_r()
[#4] 0x7ffff7f248ae → getaddrinfo()
[#5] 0x7ffff7ed5cf6 → std::sys_common::net::{impl#6}::try_from()
[#6] 0x7ffff7ece64c → core::convert::{impl#6}::try_into<(&str, u16), std::sys_common::net::LookupHost>()
[#7] 0x7ffff7ece64c → std::sys_common::net::{impl#5}::try_from()
[#8] 0x7ffff7ece64c → core::convert::{impl#6}::try_into<&str, std::sys_common::net::LookupHost>()
[#9] 0x7ffff7ece64c → std::net::addr::{impl#30}::to_socket_addrs()
───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
gef➤  bt
#0  0x00007ffff79a5196 in ?? () from /usr/lib/libnss_myhostname.so.2
#1  0x00007ffff79ad6b1 in ?? () from /usr/lib/libnss_myhostname.so.2
#2  0x00007ffff79a1045 in ?? () from /usr/lib/libnss_myhostname.so.2
#3  0x00007ffff79aa1a6 in _nss_myhostname_gethostbyname4_r () from /usr/lib/libnss_myhostname.so.2
#4  0x00007ffff7f248ae in getaddrinfo ()
#5  0x00007ffff7ed5cf6 in std::sys_common::net::{impl#6}::try_from () at library/std/src/sys_common/net.rs:205
#6  0x00007ffff7ece64c in core::convert::{impl#6}::try_into<(&str, u16), std::sys_common::net::LookupHost> () at library/core/src/convert/mod.rs:590
#7  std::sys_common::net::{impl#5}::try_from () at library/std/src/sys_common/net.rs:190
#8  core::convert::{impl#6}::try_into<&str, std::sys_common::net::LookupHost> () at library/core/src/convert/mod.rs:590
#9  std::net::addr::{impl#30}::to_socket_addrs () at library/std/src/net/addr.rs:961
#10 0x00007ffff7eb91eb in main::main ()
#11 0x00007ffff7eb9ef3 in core::ops::function::FnOnce::call_once ()
#12 0x00007ffff7eb9159 in std::sys_common::backtrace::__rust_begin_short_backtrace ()
#13 0x00007ffff7eb8fc9 in std::rt::lang_start::{{closure}} ()
#14 0x00007ffff7ecb7bf in core::ops::function::impls::{impl#2}::call_once<(), (dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe)> () at library/core/src/ops/function.rs:280
#15 std::panicking::try::do_call<&(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe), i32> () at library/std/src/panicking.rs:492
#16 std::panicking::try<i32, &(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe)> () at library/std/src/panicking.rs:456
#17 std::panic::catch_unwind<&(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe), i32> () at library/std/src/panic.rs:137
#18 std::rt::lang_start_internal::{closure#2} () at library/std/src/rt.rs:128
#19 std::panicking::try::do_call<std::rt::lang_start_internal::{closure_env#2}, isize> () at library/std/src/panicking.rs:492
#20 std::panicking::try<isize, std::rt::lang_start_internal::{closure_env#2}> () at library/std/src/panicking.rs:456
#21 std::panic::catch_unwind<std::rt::lang_start_internal::{closure_env#2}, isize> () at library/std/src/panic.rs:137
#22 std::rt::lang_start_internal () at library/std/src/rt.rs:128
#23 0x00007ffff7eb8fb1 in std::rt::lang_start ()
#24 0x00007ffff7eb9273 in main ()
gef➤  
```

</p>
</details>