linux: add -fvisibility=hidden to build flags

build/common.gypi

 # Copyright (c) 2009 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   'variables': {
     # .gyp files should set chromium_code to 1 if they build Chromium-specific
@@ skipping 475 matching lines @@
         # Enable -Werror by default, but put it in a variable so it can
         # be disabled in ~/.gyp/include.gypi on the valgrind builders.
         'variables': {
           'werror%': '-Werror',
           'no_strict_aliasing%': 0,
         },
         'cflags': [
           '<(werror)',  # See note above about the werror variable.
           '-pthread',
           '-fno-exceptions',
+          '-fvisibility=hidden',
           '-Wall',
           '-D_FILE_OFFSET_BITS=64',
         ],
         'cflags_cc': [
           #'-fno-rtti',
           '-fno-threadsafe-statics',
         ],
         'ldflags': [
           '-pthread',
         ],
@@ skipping 181 matching lines @@
           }],
           ['no_strict_aliasing==1', {
             'cflags': [
               '-fno-strict-aliasing',
             ],
           }],
           ['linux_breakpad==1', {
             'cflags': [ '-gstabs' ],
             'defines': ['USE_LINUX_BREAKPAD'],
           }],
+          ['library=="shared_library"', {
+            # When building with shared libraries, remove the visiblity-hiding
+            # flag.
+            'cflags!': [ '-fvisibility=hidden' ],
+          }],
         ],
       },
     }],
     ['OS=="mac"', {
       'target_defaults': {
         'variables': {
           # This should be 'mac_real_dsym%', but there seems to be a bug
           # with % in variables that are intended to be set to different
           # values in different targets, like this one.
           'mac_real_dsym': 0,  # Fake .dSYMs are fine in most cases.
@@ skipping 222 matching lines @@
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }
 
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