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cargo_build_script: propagate cdylib and bin link args #4097

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8 changes: 8 additions & 0 deletions cargo/private/cargo_build_script.bzl
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Original file line number Diff line number Diff line change
Expand Up @@ -335,6 +335,8 @@ def _cargo_build_script_impl(ctx):
flags_out = ctx.actions.declare_file(ctx.label.name + ".flags")
link_flags = ctx.actions.declare_file(ctx.label.name + ".linkflags")
link_search_paths = ctx.actions.declare_file(ctx.label.name + ".linksearchpaths") # rustc-link-search, propagated from transitive dependencies
cdylib_link_flags = ctx.actions.declare_file(ctx.label.name + ".cdyliblinkflags") # rustc-cdylib-link-arg, applied to cdylib crates (incl. transitively)
bin_link_flags = ctx.actions.declare_file(ctx.label.name + ".binlinkflags") # rustc-link-arg-bin[s], applied to binary crates
compilation_mode_opt_level = get_compilation_mode_opts(ctx, toolchain).opt_level

script_data = []
Expand Down Expand Up @@ -549,6 +551,8 @@ def _cargo_build_script_impl(ctx):
args.add(flags_out, format = "--flags_out=%s")
args.add(link_flags, format = "--link_flags=%s")
args.add(link_search_paths, format = "--link_search_paths=%s")
args.add(cdylib_link_flags, format = "--cdylib_link_flags=%s")
args.add(bin_link_flags, format = "--bin_link_flags=%s")
args.add(dep_env_out, format = "--dep_env_out=%s")
args.add(ctx.attr.rundir, format = "--rundir=%s")

Expand Down Expand Up @@ -613,6 +617,8 @@ def _cargo_build_script_impl(ctx):
flags_out,
link_flags,
link_search_paths,
cdylib_link_flags,
bin_link_flags,
dep_env_out,
runfiles_dir,
] + extra_output,
Expand Down Expand Up @@ -640,6 +646,8 @@ def _cargo_build_script_impl(ctx):
flags = flags_out,
linker_flags = link_flags,
link_search_paths = link_search_paths,
cdylib_link_flags = cdylib_link_flags,
bin_link_flags = bin_link_flags,
compile_data = depset([runfiles_dir] + extra_output, transitive = script_data),
),
OutputGroupInfo(
Expand Down
20 changes: 20 additions & 0 deletions cargo/private/cargo_build_script_runner/bin.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,8 @@ fn run_buildrs() -> Result<(), String> {
compile_flags_file,
link_flags_file,
link_search_paths_file,
cdylib_link_flags_file,
bin_link_flags_file,
output_dep_env_path,
stdout_path,
stderr_path,
Expand Down Expand Up @@ -215,6 +217,8 @@ fn run_buildrs() -> Result<(), String> {
compile_flags,
link_flags,
link_search_paths,
cdylib_link_flags,
bin_link_flags,
} = BuildScriptOutput::outputs_to_flags(
&buildrs_outputs,
&exec_root.to_string_lossy(),
Expand All @@ -231,6 +235,10 @@ fn run_buildrs() -> Result<(), String> {
link_search_paths_file, e
)
});
write(&cdylib_link_flags_file, cdylib_link_flags.as_bytes())
.unwrap_or_else(|e| panic!("Unable to write file {:?}: {:#?}", cdylib_link_flags_file, e));
write(&bin_link_flags_file, bin_link_flags.as_bytes())
.unwrap_or_else(|e| panic!("Unable to write file {:?}: {:#?}", bin_link_flags_file, e));

if !exec_root_links.is_empty() {
for link in exec_root_links {
Expand Down Expand Up @@ -397,6 +405,8 @@ struct Args {
compile_flags_file: String,
link_flags_file: String,
link_search_paths_file: String,
cdylib_link_flags_file: String,
bin_link_flags_file: String,
output_dep_env_path: String,
stdout_path: Option<String>,
stderr_path: Option<String>,
Expand All @@ -420,6 +430,10 @@ impl Args {
Err("Argument `link_flags_file` not provided".to_owned());
let mut link_search_paths_file: Result<String, String> =
Err("Argument `link_search_paths_file` not provided".to_owned());
let mut cdylib_link_flags_file: Result<String, String> =
Err("Argument `cdylib_link_flags_file` not provided".to_owned());
let mut bin_link_flags_file: Result<String, String> =
Err("Argument `bin_link_flags_file` not provided".to_owned());
let mut output_dep_env_path: Result<String, String> =
Err("Argument `output_dep_env_path` not provided".to_owned());
let mut stdout_path = None;
Expand All @@ -444,6 +458,10 @@ impl Args {
link_flags_file = Ok(arg.split_off("--link_flags=".len()));
} else if arg.starts_with("--link_search_paths=") {
link_search_paths_file = Ok(arg.split_off("--link_search_paths=".len()));
} else if arg.starts_with("--cdylib_link_flags=") {
cdylib_link_flags_file = Ok(arg.split_off("--cdylib_link_flags=".len()));
} else if arg.starts_with("--bin_link_flags=") {
bin_link_flags_file = Ok(arg.split_off("--bin_link_flags=".len()));
} else if arg.starts_with("--dep_env_out=") {
output_dep_env_path = Ok(arg.split_off("--dep_env_out=".len()));
} else if arg.starts_with("--stdout=") {
Expand All @@ -469,6 +487,8 @@ impl Args {
compile_flags_file: compile_flags_file.unwrap(),
link_flags_file: link_flags_file.unwrap(),
link_search_paths_file: link_search_paths_file.unwrap(),
cdylib_link_flags_file: cdylib_link_flags_file.unwrap(),
bin_link_flags_file: bin_link_flags_file.unwrap(),
output_dep_env_path: output_dep_env_path.unwrap(),
stdout_path,
stderr_path,
Expand Down
42 changes: 32 additions & 10 deletions cargo/private/cargo_build_script_runner/lib.rs
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Expand Up @@ -24,6 +24,13 @@ pub struct CompileAndLinkFlags {
pub compile_flags: String,
pub link_flags: String,
pub link_search_paths: String,
/// `-Clink-arg`s that apply only when the crate is built as a cdylib
/// (`cargo::rustc-cdylib-link-arg`). The consuming rule gates these on the
/// crate type, and propagates them transitively to cdylibs (matching cargo).
pub cdylib_link_flags: String,
/// `-Clink-arg`s that apply only when the crate is built as a binary
/// (`cargo::rustc-link-arg-bin[s]`). Gated on the crate type by the rule.
pub bin_link_flags: String,
}

/// Enum containing all the considered return value from the script
Expand All @@ -39,6 +46,10 @@ pub enum BuildScriptOutput {
Flags(String),
/// cargo::rustc-link-arg
LinkArg(String),
/// cargo::rustc-cdylib-link-arg
CdylibLinkArg(String),
/// cargo::rustc-link-arg-bin / cargo::rustc-link-arg-bins
BinLinkArg(String),
/// cargo::rustc-env
Env(String),
/// cargo::VAR=VALUE
Expand Down Expand Up @@ -100,16 +111,17 @@ impl BuildScriptOutput {
Some(BuildScriptOutput::DepEnv(format!("METADATA={}", param)))
}
}
"rustc-cdylib-link-arg" | "rustc-link-arg-bin" | "rustc-link-arg-bins" => {
// cargo::rustc-cdylib-link-arg=FLAG — Passes custom flags to a linker for cdylib crates.
// cargo::rustc-link-arg-bin=BIN=FLAG – Passes custom flags to a linker for the binary BIN.
// cargo::rustc-link-arg-bins=FLAG – Passes custom flags to a linker for binaries.
eprint!(
"Warning: build script returned unsupported directive `{}`",
split[0]
);
None
}
// cargo::rustc-cdylib-link-arg=FLAG — linker flag applied only when the
// crate is built as a cdylib.
"rustc-cdylib-link-arg" => Some(BuildScriptOutput::CdylibLinkArg(param)),
// cargo::rustc-link-arg-bins=FLAG — linker flag applied to binary targets.
"rustc-link-arg-bins" => Some(BuildScriptOutput::BinLinkArg(param)),
// cargo::rustc-link-arg-bin=BIN=FLAG — linker flag for the binary BIN.
// Bazel builds one target per crate, so the BIN selector is dropped and
// the flag applies to the owning crate's binary.
"rustc-link-arg-bin" => Some(BuildScriptOutput::BinLinkArg(
param.split_once('=').map_or(param.clone(), |(_bin, flag)| flag.to_owned()),
)),
_ => {
// cargo::KEY=VALUE — Metadata, used by links scripts.
Some(BuildScriptOutput::DepEnv(format!(
Expand Down Expand Up @@ -208,12 +220,16 @@ impl BuildScriptOutput {
let mut compile_flags = Vec::new();
let mut link_flags = Vec::new();
let mut link_search_paths = Vec::new();
let mut cdylib_link_flags = Vec::new();
let mut bin_link_flags = Vec::new();

for flag in outputs {
match flag {
BuildScriptOutput::Cfg(e) => compile_flags.push(format!("--cfg={e}")),
BuildScriptOutput::Flags(e) => compile_flags.push(e.to_owned()),
BuildScriptOutput::LinkArg(e) => compile_flags.push(format!("-Clink-arg={e}")),
BuildScriptOutput::CdylibLinkArg(e) => cdylib_link_flags.push(format!("-Clink-arg={e}")),
BuildScriptOutput::BinLinkArg(e) => bin_link_flags.push(format!("-Clink-arg={e}")),
BuildScriptOutput::LinkLib(e) => link_flags.push(format!("-l{e}")),
BuildScriptOutput::LinkSearch(e) => link_search_paths.push(format!("-L{e}")),
_ => {}
Expand All @@ -228,6 +244,8 @@ impl BuildScriptOutput {
exec_root,
out_dir,
),
cdylib_link_flags: Self::redact_flags(&cdylib_link_flags.join("\n"), exec_root, out_dir),
bin_link_flags: Self::redact_flags(&bin_link_flags.join("\n"), exec_root, out_dir),
}
}

Expand Down Expand Up @@ -336,6 +354,8 @@ mod tests {
.to_owned(),
link_flags: "-lsdfsdf".to_owned(),
link_search_paths: "-L${pwd}/bleh".to_owned(),
cdylib_link_flags: String::new(),
bin_link_flags: String::new(),
}
);
}
Expand Down Expand Up @@ -489,6 +509,8 @@ cargo::rustc-link-search=/abs/exec_root/other/path
link_flags: "".to_owned(),
link_search_paths:
"-L${pwd}/${bazel-out/cfg/bin/pkg/_bs.out_dir}\n-L${pwd}/other/path".to_owned(),
cdylib_link_flags: String::new(),
bin_link_flags: String::new(),
}
);
}
Expand Down
2 changes: 2 additions & 0 deletions rust/private/providers.bzl
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,8 @@ CrateGroupInfo = provider(
BuildInfo = provider(
doc = "A provider containing `rustc` build settings for a given Crate.",
fields = {
"bin_link_flags": "Optional[File]: file of `-Clink-arg`s to pass to rustc only when the crate is built as a binary (`cargo::rustc-link-arg-bin[s]`).",
"cdylib_link_flags": "Optional[File]: file of `-Clink-arg`s to pass to rustc only when the crate is built as a cdylib (`cargo::rustc-cdylib-link-arg`); propagated transitively to cdylibs.",
"compile_data": "Depset[File]: Compile data provided by the build script that was not copied into `out_dir`.",
"dep_env": "Optional[File]: extra build script environment variables to be set to direct dependencies.",
"flags": "Optional[File]: file containing additional flags to pass to rustc",
Expand Down
15 changes: 15 additions & 0 deletions rust/private/rustc.bzl
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Expand Up @@ -831,6 +831,7 @@ def collect_inputs(
build_script_compile_inputs, out_dir, build_env_file, build_flags_files = _process_build_scripts(
build_info = build_info,
dep_info = dep_info,
crate_type = crate_info.type,
include_link_flags = include_link_flags,
include_transitive_data = not toolchain._incompatible_do_not_include_transitive_data_in_compile_inputs,
)
Expand Down Expand Up @@ -2253,6 +2254,7 @@ def add_edition_flags(args, crate):
def _process_build_scripts(
build_info,
dep_info,
crate_type,
include_link_flags = True,
include_transitive_data = False):
"""Gathers the outputs from a target's `cargo_build_script` action.
Expand Down Expand Up @@ -2297,6 +2299,12 @@ def _process_build_scripts(
build_flags_files.append(build_info.linker_flags)
direct_inputs.append(build_info.linker_flags)

# `cargo::rustc-link-arg-bin[s]` apply only to binary targets, and (like
# cargo) only from the crate's own build script — not transitively.
if crate_type == "bin" and getattr(build_info, "bin_link_flags", None):
build_flags_files.append(build_info.bin_link_flags)
direct_inputs.append(build_info.bin_link_flags)

transitive_inputs.append(build_info.compile_data)

# We include transitive dep build_infos because cargo build scripts may generate files which get linked into the final binary.
Expand All @@ -2306,6 +2314,13 @@ def _process_build_scripts(
direct_inputs.append(dep_build_info.out_dir)
transitive_inputs.append(dep_build_info.compile_data)

# `cargo::rustc-cdylib-link-arg` applies only to cdylib targets, and (like
# cargo, see rust-lang/cargo#9562) propagates transitively to them. The
# crate's own build script is included here via `transitive_build_infos`.
if crate_type in ("cdylib", "dylib") and getattr(dep_build_info, "cdylib_link_flags", None):
build_flags_files.append(dep_build_info.cdylib_link_flags)
direct_inputs.append(dep_build_info.cdylib_link_flags)

out_dir_compile_inputs = depset(
direct_inputs,
transitive = transitive_inputs,
Expand Down
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