fix(build): don't export all symbols to dynamic symbol table (#16171)

Currently, we use `-rdynamic` for exporting Node API symbols to the
symbol table. `-rdynamic` will export *all* symbols, that means
previously unused functions will not be optimized away introducing a lot
of binary bloat. 

This patch uses `-exported_symbol` and `--export-dynamic-symbol` link
flags (not as universal as `-rdynamic`) to only mark Node API symbols to
be put in the dynamic symbol table.

1 files changed, 30 insertions, 1 deletions

diff --git a/cli/build.rs b/cli/build.rs
index aaa29a6d0..c1bc3305e 100644
--- a/cli/build.rs
+++ b/cli/build.rs
@@ -344,7 +344,36 @@ fn main() {
   );
 
   #[cfg(not(target_os = "windows"))]
-  println!("cargo:rustc-link-arg-bin=deno=-rdynamic");
+  {
+    // Load the symbols file generated by the `napi_sym` macro.
+    #[derive(serde::Deserialize)]
+    struct Symbols {
+      symbols: Vec<String>,
+    }
+    let symbols_json =
+      std::fs::read_to_string("../tools/napi/symbol_exports.json").expect(
+        "Missing tools/napi/symbol_exports.json! This is a bug in napi_sym",
+      );
+    let symbols: Symbols = serde_json::from_str(&symbols_json)
+      .expect("tools/napi/symbol_exports.json is not valid JSON");
+
+    // Don't export all symbols into the dynamic symbol table. -rdynamic exports *all* symbols introducing binary bloat.
+    // We only need to export Node API symbols.
+    for symbol in symbols.symbols {
+      // TODO(@littledivy): We _might_ hit an argument size limit?
+      // Maybe use `--export-dynamic-symbol-list` / `--exported_symbols_list` instead? https://reviews.llvm.org/D107317
+      #[cfg(target_os = "macos")]
+      println!(
+        "cargo:rustc-link-arg-bin=deno=-Wl,-exported_symbol,_{}",
+        symbol
+      );
+      #[cfg(target_os = "linux")]
+      println!(
+        "cargo:rustc-link-arg-bin=deno=-Wl,--export-dynamic-symbol={}",
+        symbol
+      );
+    }
+  }
 
   // To debug snapshot issues uncomment:
   // op_fetch_asset::trace_serializer();