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Clarify build.rs C compiler and linker configuration. #1697

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merged 4 commits into from
Oct 6, 2023
Merged

Clarify build.rs C compiler and linker configuration. #1697

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84d41c7
build.rs: Remove empty and useless `LD_FLAGS`.
briansmith Oct 5, 2023
6ca3819
build.rs: Clarify compiler configuration.
briansmith Oct 5, 2023
2eea794
build.rs: Don't try to manually set `-fPIC`.
briansmith Oct 5, 2023
34f6ec8
build.rs: Don't try to set linker flags since we're not linking.
briansmith Oct 5, 2023
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53 changes: 24 additions & 29 deletions build.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -160,8 +160,6 @@ fn cpp_flags(compiler: &cc::Tool) -> &'static [&'static str] {
}
}

const LD_FLAGS: &[&str] = &[];

// None means "any OS" or "any target". The first match in sequence order is
// taken.
const ASM_TARGETS: &[AsmTarget] = &[
Expand Down Expand Up @@ -389,8 +387,9 @@ fn pregenerate_asm_main() {
force_warnings_into_errors: true,
};

let b = new_build(&target, &pregenerated_tmp);
for src in srcs {
compile(&src, &target, &pregenerated_tmp, &pregenerated);
compile(&b, &src, &target, &pregenerated_tmp, &pregenerated);
}
}
}
Expand Down Expand Up @@ -485,37 +484,31 @@ fn build_c_code(
);
}

fn new_build(target: &Target, include_dir: &Path) -> cc::Build {
let mut b = cc::Build::new();
configure_cc(&mut b, target, include_dir);
b
}

fn build_library(
target: &Target,
out_dir: &Path,
lib_name: &str,
srcs: &[PathBuf],
additional_srcs: &[PathBuf],
) {
let mut c = new_build(target, out_dir);

// Compile all the (dirty) source files into object files.
let objs = additional_srcs
.iter()
.chain(srcs.iter())
.map(|f| compile(f, target, out_dir, out_dir))
.map(|f| compile(&c, f, target, out_dir, out_dir))
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Now all the calls to compile() share a single build configuration that is constructed once per library, instead of once per source file.

.collect::<Vec<_>>();

// Rebuild the library if necessary.
let lib_path = PathBuf::from(out_dir).join(format!("lib{}.a", lib_name));

let mut c = cc::Build::new();

for f in LD_FLAGS {
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LD_FLAGS was empty so this wasn't doing anything.

let _ = c.flag(f);
}
match target.os.as_str() {
"macos" => {
let _ = c.flag("-fPIC");
let _ = c.flag("-Wl,-dead_strip");
}
_ => {
let _ = c.flag("-Wl,--gc-sections");
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}
}
for o in objs {
let _ = c.object(o);
}
Expand All @@ -535,14 +528,14 @@ fn build_library(
println!("cargo:rustc-link-lib=static={}", lib_name);
}

fn compile(p: &Path, target: &Target, include_dir: &Path, out_dir: &Path) -> String {
fn compile(b: &cc::Build, p: &Path, target: &Target, include_dir: &Path, out_dir: &Path) -> String {
let ext = p.extension().unwrap().to_str().unwrap();
if ext == "o" {
p.to_str().expect("Invalid path").into()
} else {
let out_file = obj_path(out_dir, p);
let cmd = if target.os != WINDOWS || ext != "asm" {
cc(p, ext, target, include_dir, &out_file)
cc(b, p, ext, &out_file)
} else {
nasm(p, &target.arch, include_dir, &out_file)
};
Expand All @@ -561,9 +554,7 @@ fn obj_path(out_dir: &Path, src: &Path) -> PathBuf {
out_path
}

fn cc(file: &Path, ext: &str, target: &Target, include_dir: &Path, out_file: &Path) -> Command {
let mut c = cc::Build::new();

fn configure_cc(c: &mut cc::Build, target: &Target, include_dir: &Path) {
// FIXME: On Windows AArch64 we currently must use Clang to compile C code
if target.os == WINDOWS && target.arch == AARCH64 && !c.get_compiler().is_like_clang() {
let _ = c.compiler("clang");
Expand All @@ -573,10 +564,6 @@ fn cc(file: &Path, ext: &str, target: &Target, include_dir: &Path, out_file: &Pa

let _ = c.include("include");
let _ = c.include(include_dir);
match ext {
"c" | "S" => (),
e => panic!("Unsupported file extension: {:?}", e),
};
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Moved to the top of the new cc().

for f in cpp_flags(&compiler) {
let _ = c.flag(f);
}
Expand Down Expand Up @@ -635,9 +622,17 @@ fn cc(file: &Path, ext: &str, target: &Target, include_dir: &Path, out_file: &Pa
// http://www.openwall.com/lists/musl/2015/06/17/1
let _ = c.flag("-U_FORTIFY_SOURCE");
}
}

fn cc(b: &cc::Build, file: &Path, ext: &str, out_file: &Path) -> Command {
match ext {
"c" | "S" => (),
e => panic!("Unsupported file extension: {:?}", e),
};

let obj_opt = if compiler.is_like_msvc() { "/Fo" } else { "-o" };
let mut c = c.get_compiler().to_command();
let cc = b.get_compiler();
let obj_opt = if cc.is_like_msvc() { "/Fo" } else { "-o" };
let mut c = cc.to_command();
let _ = c
.arg("-c")
.arg(format!(
Expand Down
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