GN Don't enable linker version script for components

build/config/BUILDCONFIG.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # =============================================================================
 # PLATFORM SELECTION
 # =============================================================================
 #
 # There are two main things to set: "os" and "cpu". The "toolchain" is the name
 # of the GN thing that encodes combinations of these things.
@@ skipping 531 matching lines @@
 }
 set_defaults("shared_library") {
   configs = _shared_library_configs
 }
 set_defaults("loadable_module") {
   configs = _shared_library_configs
 }
 if (is_component_build) {
   set_defaults("component") {
     configs = _shared_library_configs
+    if (is_android) {
+      configs -= [ "//build/config/android:hide_native_jni_exports" ]
+    }
   }
 }
 
 # Source set defaults (also for components in non-component mode).
 set_defaults("source_set") {
   configs = _native_compiler_configs
 }
 if (!is_component_build) {
   set_defaults("component") {
     configs = _native_compiler_configs
   }
 }
 
 # Test defaults.
 set_defaults("test") {
   if (is_android) {
     configs = _shared_library_configs
   } else {
     configs = _executable_configs
   }
 }
 
 # ==============================================================================
 # COMPONENT SETUP
 # ==============================================================================
 
-if (is_component_build) {
-  _component_mode = "shared_library"
-} else {
-  _component_mode = "source_set"
-}
 template("component") {
+  # Some targets (e.g. //base) should user static_library rather than source_set

[brettw, 2016/01/04 22:24:53]

...rather than source set in non-component builds...

Also, can you document this above the component template instead? It should say
the arguments are the same as a normal library with this addition: <current
thing you have>

[agrieve, 2016/01/05 02:46:47]

Done.

+  # in order to not link unused object files.
+  _never_use_source_set =
+      defined(invoker.never_use_source_set) && invoker.never_use_source_set

[brettw, 2016/01/04 22:24:53]

I'd feel better if this parameter was called
"invoker.component_never_use_source_set" which will make the caller in base more
clear.

[agrieve, 2016/01/05 02:46:47]

Done.

+  assert(_never_use_source_set || true)  # Mark as used.
+  if (is_component_build) {
+    _component_mode = "shared_library"
+  } else if (_never_use_source_set) {

[brettw, 2016/01/04 22:24:53]

Why not just write:
  } else if (defined(invoker.component_never_use_source_set) &&
invoker.component_never_use_source_set) {

and avoid both the temporary and the weird assert thing above? I think mine is
clear enough.

[agrieve, 2016/01/05 02:46:47]

I tried this at first, but it complains of an unused variable when
is_component_build == true (presumably since the else-if never needs to be
evaluated).

+    _component_mode = "static_library"
+  } else {
+    _component_mode = "source_set"
+  }
   target(_component_mode, target_name) {
     forward_variables_from(invoker, "*")
 
     # All shared libraries must have the sanitizer deps to properly link in
     # asan mode (this target will be empty in other cases).
     if (!defined(deps)) {
       deps = []
     }
     deps += [ "//build/config/sanitizers:deps" ]
   }
 }