Don't set -fvisibility=hidden for iOS Debug.

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 454 matching lines @@
     "//build/config/win:nominmax",
     "//build/config/win:unicode",
     "//build/config/win:winver",
   ]
 }
 if (current_os == "winrt_81" || current_os == "winrt_81_phone" ||
     current_os == "winrt_10") {
   _native_compiler_configs += [ "//build/config/win:target_winrt" ]
 }
 if (is_posix) {
-  _native_compiler_configs += [
-    "//build/config/gcc:no_exceptions",
-    "//build/config/gcc:symbol_visibility_hidden",
-  ]
+  _native_compiler_configs += [ "//build/config/gcc:no_exceptions" ]
+
+  # XCTests require symbols to not be hidden.
+  if (!is_ios || is_release) {
+    _native_compiler_configs +=
+        [ "//build/config/gcc:symbol_visibility_hidden" ]

[brettw, 2015/12/12 23:53:18]

Let's do this: make a new config in build/config/gcc like:

config("default_symbol_visibility") {
  if (!is_posix || is_release) {
    configs = [ ":symbol_visibility_hidden" ]
  }
}

Then you can unconditionally reference the default symbol visibility from here.

Can you also write a better comment? I don't know what XCTests are or what this
might have to do with debug vs. release.

[baxley, 2015/12/14 18:46:52]

Done. Thanks for the detailed explanation.

+  }
 }
 
 if (is_android) {
   _native_compiler_configs +=
       [ "//build/config/android:default_cygprofile_instrumentation" ]
 }
 
 if (is_clang && !is_nacl) {
   _native_compiler_configs += [
     "//build/config/clang:find_bad_constructs",
@@ skipping 96 matching lines @@
     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" ]
   }
 }