feat: query xcrun to find the correct location of libc(++) on MacOS

Cargo.toml

@@ -17,8 +17,7 @@ links = "leanshared"
 [features]
 small_allocator = []
 extern = []
-static = []
-default = ["small_allocator", "static"]
+default = ["small_allocator"]
 
 [dependencies]
 libc = { version = "0.2", default-features = false }

build.rs

@@ -1,6 +1,47 @@
 use std::path::PathBuf;
 use std::process::Command;
 
+fn cargo_add_ld_options() {
+    // Run the command 'leanc --print-ldflags'
+    let output = Command::new("leanc")
+        .arg("--print-ldflags")
+        .output()
+        .expect("Failed to execute leanc command");
+
+    // Check if the command was successful
+    if output.status.success() {
+        // Convert the output to a string
+        let output_str = String::from_utf8(output.stdout).expect("Invalid UTF-8 in output");
+
+        // Split the output by '-L' and get the part after '-L'
+        let parts: Vec<&str> = output_str.split("-L").collect();
+        if parts.len() < 2 {
+            eprintln!("Error: No ldflags found after -L");
+            return;
+        }
+        let ld_search_path = parts[1].split_whitespace().next().unwrap_or_default();
+
+        // Pass search_path to Cargo as arguments
+        println!("cargo:rustc-link-search=native={}", ld_search_path);
+
+        let lib_names : Vec<&str> = parts[1].split(" ").skip(2).map(|part| {
+            // drop the '-l' part.
+            part.split_whitespace().next().unwrap_or_default().strip_prefix("-l").unwrap_or_default()
+
+        }).collect();
+
+        for lib_name in lib_names.iter() {
+            println!("cargo:rustc-link-lib={}", lib_name);
+        }
+        println!("cargo::warning=error: lib names: {:?}", lib_names);
+
+    } else {
+        // Print an error message if the command failed
+        println!("cargo::warning='Error: leanc command failed with status {:?}", output.status);
+    }
+}
+
+
 fn main() {
     if let Ok(docs_rs) = std::env::var("DOCS_RS") {
         // Detected build on `docs.rs`, so skip trying to link in Lean and just build docs
@@ -31,53 +72,23 @@ fn main() {
         lean_dir.join("lib/lean")
     };
 
-    if !cfg!(feature = "static") {
-        // Step 2: check libleanshared.so/libleanshared.dylib/libleanshared.dll is actually there, just for cleaner error messages
-        let mut shared_lib = lib_dir.clone();
-        let exists = if cfg!(target_os = "windows") {
-            shared_lib.push("libleanshared.dll");
-            shared_lib.exists()
-        } else if cfg!(target_os = "macos") {
-            shared_lib.push("libleanshared.dylib");
-            shared_lib.exists()
-        } else if cfg!(unix) {
-            shared_lib.push("libleanshared.so");
-            shared_lib.exists()
-        } else {
-            true
-        };
-        if !exists {
-            panic!(
-                "{} was not found. We errored, as this would probably cause a linking failure later",
-                shared_lib.display()
-            );
-        }
-
-        // Step 3: actually link with the library
-        println!("cargo:rustc-link-search={}", lib_dir.display());
-        println!("cargo:rustc-link-lib=leanshared");
-        println!("cargo:rustc-link-arg=-Wl,-rpath,{}", lib_dir.display());
-    } else if cfg!(feature = "extern") {
-        println!("cargo:rustc-link-search={}/lib/lean", lean_dir.display());
-        println!("cargo:rustc-link-search={}/lib", lean_dir.display());
-        for lib in ["Lean", "Init", "leanrt", "leancpp", "gmp", "c++", "c++abi"] {
-            println!("cargo:rustc-link-lib=static={lib}");
-        }
-    } else {
-        println!("cargo:rustc-link-search={}/lib", lean_dir.display());
-        println!("cargo:rustc-link-search={}/lib/lean", lean_dir.display());
-        for libs in [["Lean", "leancpp"], ["Init", "leanrt"]] {
-            println!("cargo:rustc-link-arg=-Wl,--start-group");
-            for lib in libs {
-                println!("cargo:rustc-link-lib=static={lib}");
-            }
-            println!("cargo:rustc-link-arg=-Wl,--end-group");
-        }
-        for lib in ["Lake", "c++", "c++abi"] {
-            println!("cargo:rustc-link-lib=static={lib}");
-        }
-        for lib in ["m", "dl", "gmp"] {
-            println!("cargo:rustc-link-lib=dylib={lib}");
-        }
+    // To find libc++ on macOS, We must find the path to XCode, which apple enjoys
+    // changing each macOS release.
+    // Thus, we do this in a robust fashion by querying `xcrun`.
+    if cfg!(target_os = "macos") {
+        let xcrun_output = Command::new("xcrun")
+          .args(["--show-sdk-path"])
+          .output()
+          .expect("failed to execute `xcrun --show-sdk-path`, which is used to find the location of MacOS platform libraries. Please ensure that XCode is installed.");
+        let libcpp_path = PathBuf::from(String::from_utf8(xcrun_output.stdout)
+            .expect("Path returned by `xcrun --show-sdk-path` is invalid UTF-8. This must never happen.").trim())
+          .join("usr/lib");
+        println!("cargo:rustc-link-search={}", libcpp_path.display());
     }
+
+    println!("cargo:rustc-link-search={}/lib", lean_dir.display());
+    println!("cargo:rustc-link-search={}/lib/lean", lean_dir.display());
+
+    cargo_add_ld_options();
+
 }