[MacPorts] #69138: rust @1.75.0 : Does not build on macOS 10.11.6 - missing _getentropy and _clock_gettime

[MacPorts]

#69138: rust @1.75.0 : Does not build on macOS 10.11.6 - missing  _getentropy and
_clock_gettime
------------------------+---------------------------------
  Reporter:  snowflake  |      Owner:  MarcusCalhoun-Lopez
      Type:  defect     |     Status:  closed
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:  2.8.99
Resolution:  fixed      |   Keywords:
      Port:  rust       |
------------------------+---------------------------------

Comment (by mqudsi):

 Not sure if I should comment here or possibly open a different issue, but
 is there any way for the legacy-support shims to be visible to downstream
 users of `rustc` linking against its standard library?

 For example, the `rand` crate assumes that since `rustc` bumped its
 minimum supported macOS version to one with `_getentropy()` and
 `_clock_gettime()`, it can just call them. But that causes undefined
 symbol linker errors even when using a macports legacy-support-infused
 rust toolchain (rust/cargo 1.78.0 under 10.10) to build the project with
 the `rand` dependency. As `rand` is quite a foundational crate, this
 limits compatibility significantly (the last `rand` version without the
 hard `_getentropy()` dependency was 0.7.x which is not semver-compatible
 with the current 0.8.x rand releases and requires a lot of hacking to
 dependent projects to get them to run under 0.7.x).

 Is there any way we can make the legacy support `_getentroy()` and
 `_clock_gettime()` shims transitively visible to its dependents?

 The linker error:

 {{{
 error: linking with `cc` failed: exit status: 1
 <snip>
           Undefined symbols for architecture x86_64:
             "_clock_gettime", referenced from:
 std::sys::pal::unix::time::Timespec::now::hf41285c15e0a285b
 (.llvm.4974563244208805110) in libstd-dea1dec033daebae.rlib(std-
 dea1dec033daebae.std.4e58b1c7d3f5f121-cgu.05.rcgu.o)
             "_getentropy", referenced from:
 std::sys::pal::unix::rand::imp::fill_bytes::h39617d8376b4a809 in libstd-
 dea1dec033daebae.rlib(std-
 dea1dec033daebae.std.4e58b1c7d3f5f121-cgu.14.rcgu.o)
 }}}

 As an fyi/aside, I tried to define my own `_gentropy()` shim in rust (in
 the same project that uses `rand`), but it doesn't work as the linker is
 searching for a dynamically exported symbol and is not considering static
 symbols exported by the same project (this kind of stuff used to work in
 C++ — or maybe it's actually a macOS-specific limitation that stops it
 from working?):

 {{{#!rust
 #[no_mangle]
 pub unsafe fn _getentropy(buf: *mut core::ffi::c_void, buflen: usize) ->
 core::ffi::c_int {
     use std::io::Read;

     let slice = std::slice::from_raw_parts_mut(buf as *mut u8, buflen);
     let mut rand = match std::fs::File::open("/dev/urandom") {
         Ok(file) => file,
         Err(_) => return -1,
     };
     match rand.read_exact(slice) {
         Ok(_) => 0,
         _ => -1,
     }
 }
 }}}

-- 
Ticket URL: <https://trac.macports.org/ticket/69138#comment:21>
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