build: build v8 with -fvisibility=hidden on macOS

joyeecheung · marco-ippolito · commit cccd2aba6e3d · 2025-03-06T13:23:42.000+01:00
V8 should be built with -fvisibility=hidden, otherwise the resulting binary would contain unnecessary symbols. In particular, on macOS, this leads to 5000+ weak symbols resolved at runtime, leading to a startup regression. On macOS this also reduces the binary size about ~10MB. It's only enabled on macOS in this patch as gcc can time out or run out of memory on some machines in the CI with -fvisibility=hidden. PR-URL: #56275 Fixes: nodejs/performance#180 Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com> Reviewed-By: Daniel Lemire <daniel@lemire.me> Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com> Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com> Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Michaël Zasso <targos@protonmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Chengzhong Wu <legendecas@gmail.com> Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>
diff --git a/tools/v8_gypfiles/v8.gyp b/tools/v8_gypfiles/v8.gyp
@@ -41,6 +41,19 @@
         'AdditionalOptions': ['/utf-8']
       }
     },
+    'conditions': [
+      ['OS=="mac"', {
+        # Hide symbols that are not explicitly exported with V8_EXPORT.
+        # TODO(joyeecheung): enable it on other platforms. Currently gcc times out
+        # or run out of memory with -fvisibility=hidden on some machines in the CI.
+        'xcode_settings': {
+          'GCC_SYMBOLS_PRIVATE_EXTERN': 'YES',  # -fvisibility=hidden
+        },
+        'defines': [
+          'BUILDING_V8_SHARED',  # Make V8_EXPORT visible.
+        ],
+      }],
+    ],
   },
   'targets': [
     {
