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Add LIB_SYS_TRY_SHARED ENV var to try to link with shared library #206

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Add LIB_SYS_TRY_SHARED ENV var to try to link with shared library #206

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4 changes: 3 additions & 1 deletion build.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -82,10 +82,12 @@ fn main() {
// Apple platforms have libz.1.dylib, and it's usually available even when
// cross compiling (via fat binary or in the target's Xcode SDK)
let cross_compiling = target != host;
let try_link_with_shared =
env::var("LIB_SYS_TRY_SHARED").unwrap_or(String::new()) == "1";
Comment on lines +85 to +86
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@polarathene polarathene Nov 13, 2025 •
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This is not needed. Use the existing ENV:

libz-sys/build.rs

Lines 37 to 38 in 80c597a

let want_static =
cfg!(feature = "static") || env::var("LIBZ_SYS_STATIC").unwrap_or(String::new()) == "1";

So something like the below function would work just fine to support an optional ENV (0/1) for overriding a dependency that vendors a lib in via the static feature? (which would otherwise be respected if no override ENV exists at build-time)

fn should_link_static() -> bool {
  let want_static_env: Option<&'static str> = option_env!("LIBZ_SYS_STATIC");
  let want_static_cfg = cfg!(feature = "static");

  want_static_env
    .and_then(|value: &str| value.parse::<u8>().ok())
    .and_then(|b| match b {
      0 => Some(false),
      1 => Some(true),
      _ => None,
    })
    .unwrap_or(want_static_cfg)
}

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@Byron Byron Nov 14, 2025

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Thanks for putting the logic into the clear, to me that makes sense and allows to override cargo features using environment variables.

if target.contains("msvc")
|| target.contains("pc-windows-gnu")
|| want_static
|| (cross_compiling && !target.contains("-apple-"))
|| !try_link_with_shared && (cross_compiling && !target.contains("-apple-"))
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@polarathene polarathene Nov 13, 2025

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This line is no longer relevant, and should be left alone as it is now currently:

libz-sys/build.rs

Lines 81 to 86 in 80c597a

if target.contains("msvc")
|| target.contains("pc-windows-gnu")
|| want_static
{
return build_zlib(&mut cfg, &target);
}

{
return build_zlib(&mut cfg, &target);
}
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