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feat: support build and link dynamic library #1444

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21f2b00
feat: support build and link dynamic library
westhide Mar 30, 2025
1e8de34
fix: cargo clippy lint
westhide Mar 30, 2025
f9e4a70
feat: support build and link dynamic library
westhide Mar 30, 2025
a6da499
feat: support build and link dynamic library
westhide Mar 31, 2025
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2 changes: 1 addition & 1 deletion src/command_helpers.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -46,7 +46,7 @@ impl CargoOutput {
warnings: true,
output: OutputKind::Forward,
debug: match std::env::var_os("CC_ENABLE_DEBUG_OUTPUT") {
Some(v) => v != "0" && v != "false" && v != "",
Some(v) => v != "0" && v != "false" && !v.is_empty(),
None => false,
},
checked_dbg_var: Arc::new(AtomicBool::new(false)),
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4 changes: 2 additions & 2 deletions src/flags.rs
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Expand Up @@ -185,7 +185,7 @@ impl<'this> RustcCodegenFlags<'this> {
};

let clang_or_gnu =
matches!(family, ToolFamily::Clang { .. }) || matches!(family, ToolFamily::Gnu { .. });
matches!(family, ToolFamily::Clang { .. }) || matches!(family, ToolFamily::Gnu);

// Flags shared between clang and gnu
if clang_or_gnu {
Expand Down Expand Up @@ -315,7 +315,7 @@ impl<'this> RustcCodegenFlags<'this> {
}
}
}
ToolFamily::Gnu { .. } => {}
ToolFamily::Gnu => {}
ToolFamily::Msvc { .. } => {
// https://learn.microsoft.com/en-us/cpp/build/reference/guard-enable-control-flow-guard
if let Some(value) = self.control_flow_guard {
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55 changes: 43 additions & 12 deletions src/lib.rs
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Expand Up @@ -332,6 +332,7 @@ pub struct Build {
shell_escaped_flags: Option<bool>,
build_cache: Arc<BuildCache>,
inherit_rustflags: bool,
link_shared_flag: bool,
}

/// Represents the types of errors that may occur while using cc-rs.
Expand Down Expand Up @@ -459,6 +460,7 @@ impl Build {
shell_escaped_flags: None,
build_cache: Arc::default(),
inherit_rustflags: true,
link_shared_flag: false,
}
}

Expand Down Expand Up @@ -1227,6 +1229,14 @@ impl Build {
self
}

/// Configure whether cc should build dynamic library and link with `rustc-link-lib=dylib`
///
/// This option defaults to `false`.
pub fn link_shared_flag(&mut self, link_shared_flag: bool) -> &mut Build {
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When reading this as a user, it is not really clear how this differs from shared_flag.

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Stated another way: When would you ever want shared_flag(true) but not link_shared_flag(true)? And vice-versa?

self.link_shared_flag = link_shared_flag;
self
}

#[doc(hidden)]
pub fn __set_env<A, B>(&mut self, a: A, b: B) -> &mut Build
where
Expand Down Expand Up @@ -1380,6 +1390,18 @@ impl Build {
Ok(is_supported)
}

fn get_canonical_library_names(name: &str) -> (&str, String, String) {
let lib_striped = name.strip_prefix("lib").unwrap_or(name);
let static_striped = lib_striped.strip_suffix(".a").unwrap_or(lib_striped);
let lib_name = lib_striped.strip_suffix(".so").unwrap_or(static_striped);

(
lib_name,
format!("lib{lib_name}.a"),
format!("lib{lib_name}.so"),
)
}

/// Run the compiler, generating the file `output`
///
/// This will return a result instead of panicking; see [`Self::compile()`] for
Expand All @@ -1396,21 +1418,25 @@ impl Build {
}
}

let (lib_name, gnu_lib_name) = if output.starts_with("lib") && output.ends_with(".a") {
(&output[3..output.len() - 2], output.to_owned())
} else {
let mut gnu = String::with_capacity(5 + output.len());
gnu.push_str("lib");
gnu.push_str(output);
gnu.push_str(".a");
(output, gnu)
};
let (lib_name, static_name, dynlib_name) = Self::get_canonical_library_names(output);
let dst = self.get_out_dir()?;

let objects = objects_from_files(&self.files, &dst)?;

self.compile_objects(&objects)?;
self.assemble(lib_name, &dst.join(gnu_lib_name), &objects)?;

if self.link_shared_flag {
let objects = objects.iter().map(|o| o.dst.clone()).collect::<Vec<_>>();

let mut command = self.try_get_compiler()?.to_command();
let cmd = command
.args(["-shared", "-o"])
.arg(dst.join(dynlib_name))
.args(&objects);
run(cmd, &self.cargo_output)?;
}

self.assemble(lib_name, &dst.join(static_name), &objects)?;
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I think we don't need to run assemble if it's already dynamically linked?

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Should we consider support dll on windows?

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I think we don't need to run assemble if it's already dynamically linked?

Sure, fixed.

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Should we consider support dll on windows?

Can you elaborate on that please?

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@westhide westhide Mar 31, 2025 •
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Windows ddl is complicated, i have not idea how to add a dynamic library test case for it. It's weird as cl.exe require a main function to build a dll library.

With this source file, it will cause a Entry Point Not Found error

#include <windows.h>
void msvc() {}

Test pass if add a main function

#include <windows.h>
void msvc() {}
void main() {}

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Thanks for explanation, I'm ok with it not tested, if you have time to add another test for it I would greatly appreciate


let target = self.get_target()?;
if target.env == "msvc" {
Expand All @@ -1435,8 +1461,13 @@ impl Build {
}

if self.link_lib_modifiers.is_empty() {
self.cargo_output
.print_metadata(&format_args!("cargo:rustc-link-lib=static={}", lib_name));
if self.link_shared_flag {
self.cargo_output
.print_metadata(&format_args!("cargo:rustc-link-lib=dylib={}", lib_name));
} else {
self.cargo_output
.print_metadata(&format_args!("cargo:rustc-link-lib=static={}", lib_name));
}
} else {
self.cargo_output.print_metadata(&format_args!(
"cargo:rustc-link-lib=static:{}={}",
Expand Down
12 changes: 6 additions & 6 deletions src/target/parser.rs
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Expand Up @@ -477,13 +477,13 @@ mod tests {
let (full_arch, _rest) = target.split_once('-').expect("target to have arch");

let mut target = TargetInfo {
full_arch: full_arch.into(),
arch: "invalid-none-set".into(),
vendor: "invalid-none-set".into(),
os: "invalid-none-set".into(),
env: "invalid-none-set".into(),
full_arch,
arch: "invalid-none-set",
vendor: "invalid-none-set",
os: "invalid-none-set",
env: "invalid-none-set",
// Not set in older Rust versions
abi: "".into(),
abi: "",
};

for cfg in cfgs.lines() {
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2 changes: 1 addition & 1 deletion tests/cc_env.rs
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Expand Up @@ -117,7 +117,7 @@ fn clang_cl() {
for exe_suffix in ["", ".exe"] {
let test = Test::clang();
let bin = format!("clang{exe_suffix}");
env::set_var("CC", &format!("{bin} --driver-mode=cl"));
env::set_var("CC", format!("{bin} --driver-mode=cl"));
let test_compiler = |build: cc::Build| {
let compiler = build.get_compiler();
assert_eq!(compiler.path(), Path::new(&*bin));
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4 changes: 2 additions & 2 deletions tests/test.rs
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Expand Up @@ -532,8 +532,8 @@ fn gnu_apple_sysroot() {
test.shim("fake-gcc")
.gcc()
.compiler("fake-gcc")
.target(&target)
.host(&target)
.target(target)
.host(target)
.file("foo.c")
.compile("foo");

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Documentation on compile should also be updated to reflect the new renaming rules.

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If we actually want to support shared libraries, we should consider a .linker and .get_linker similar to .archiver and .get_archiver, as well as maybe allowing overriding the linker with an LD env var (?)

Though if we allow using a raw linker (e.g. invoke rust-lld binary instead of cc), we're getting into hairy territory of needing to know how to invoke the linker if it's not a compiler driver.

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(Which again is why I'm really not in favour of it).

Expand Down