Support target-specific rustflags

Author: lu-zero

Cargo.toml

@@ -45,6 +45,7 @@ glob = "0.3"
 itertools = "0.14"
 implib = "0.4.0"
 object = { version = "0.37.1", default-features = false, features = ["std", "read_core", "pe"] }
+cargo-platform = "0.3.1"
 
 [features]
 default = []

README.md

@@ -154,6 +154,10 @@ rustflags = "-Cpanic=abort"
 # Used to disable the generation of additional import library file in platforms
 # that have the concept such as Windows
 import_library = false
+
+[package.metadata.capi.library.target.'cfg(target_os = "linux")']
+# Add target-specific rustflags, the are folded with the main rustflags above
+rustflags = "-Clink-arg=-Wl,--version-script=assets/version.map"
 ```
 
 ### Custom data install

src/build.rs

@@ -2,6 +2,7 @@ use std::collections::HashMap;
 use std::hash::{DefaultHasher, Hash, Hasher};
 use std::io::{ErrorKind, Read};
 use std::path::{Path, PathBuf};
+use std::str::FromStr;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
 
@@ -14,6 +15,7 @@ use cargo::util::interning::InternedString;
 use cargo::{CliResult, GlobalContext};
 
 use anyhow::Context as _;
+use cargo_platform::Platform;
 use cargo_util::paths::{copy, create_dir_all, open, read, read_bytes, write};
 use implib::def::ModuleDef;
 use implib::{Flavor, ImportLibrary, MachineType};
@@ -648,17 +650,39 @@ fn load_manifest_capi_config(
             });
         }
 
+        fn make_args(args: &str) -> impl Iterator<Item = String> + use<'_> {
+            args.split(' ')
+                .map(str::trim)
+                .filter(|s| !s.is_empty())
+                .map(str::to_string)
+        }
+
         import_library = library
             .get("import_library")
             .and_then(|v| v.as_bool())
             .unwrap_or(true);
+
         if let Some(args) = library.get("rustflags").and_then(|v| v.as_str()) {
+            rustflags.extend(make_args(args));
+        }
+
+        if let Some(args) = library.get("target").and_then(|v| v.as_table()) {
             let args = args
-                .split(' ')
-                .map(str::trim)
-                .filter(|s| !s.is_empty())
-                .map(str::to_string);
-            rustflags.extend(args);
+                .iter()
+                .filter_map(|(p, v)| {
+                    if Platform::from_str(&p)
+                        .ok()
+                        .is_some_and(|p| p.matches(name, &rustc_target.cfg))
+                    {
+                        v.as_str()
+                    } else {
+                        None
+                    }
+                })
+                .map(make_args)
+                .flatten();
+
+            rustflags.extend(args)
         }
     }
 

src/target.rs

@@ -1,9 +1,11 @@
 use std::env::consts;
 use std::path::{Path, PathBuf};
-
-use anyhow::*;
+use std::str::FromStr;
 
 use crate::build::CApiConfig;
+use anyhow::*;
+use cargo::core::compiler::CompileTarget;
+use cargo_platform::Cfg;
 
 /// Split a target string to its components
 ///
@@ -16,15 +18,18 @@ pub struct Target {
     // pub vendor: String,
     pub os: String,
     pub env: String,
+    pub target: Option<CompileTarget>,
+    pub cfg: Vec<Cfg>,
 }
 
 impl Target {
-    pub fn new<T: AsRef<std::ffi::OsStr>>(
+    pub fn new<T: AsRef<std::ffi::OsStr> + AsRef<str>>(
         target: Option<T>,
         is_target_overridden: bool,
-    ) -> Result<Self, anyhow::Error> {
+    ) -> Result<Self> {
         let rustc = std::env::var("RUSTC").unwrap_or_else(|_| "rustc".into());
         let mut cmd = std::process::Command::new(rustc);
+        let target = target.as_ref();
 
         cmd.arg("--print").arg("cfg");
         if let Some(target) = target {
@@ -46,18 +51,37 @@ impl Target {
 
             let s = std::str::from_utf8(&out.stdout).unwrap();
 
+            let lines = s.lines();
+
+            let cfg = lines
+                .map(|line| Ok(Cfg::from_str(line)?))
+                .collect::<Result<Vec<_>>>()
+                .with_context(|| {
+                    format!(
+                        "failed to parse the cfg from `rustc --print=cfg`, got:\n{}",
+                        s
+                    )
+                })?;
+
             Ok(Target {
                 arch: match_re(arch_re, s),
                 // vendor: match_re(vendor_re, s),
                 os: match_re(os_re, s),
                 env: match_re(env_re, s),
                 is_target_overridden,
+                target: target.map(|t| CompileTarget::new(t.as_ref())).transpose()?,
+                cfg,
             })
         } else {
             Err(anyhow!("Cannot run {:?}", cmd))
         }
     }
 
+    /// Produce the target name, if known
+    pub fn name(&self) -> Option<&str> {
+        self.target.as_ref().map(|t| t.short_name())
+    }
+
     /// Build a list of linker arguments
     pub fn shared_object_link_args(
         &self,