build: Updates for AIX npm support - part 1

This PR is the first step enabling support for native modules
for AIX.  The main issue is that unlike linux where all
symbols within the Node executable are available to the shared
library for a native module (npm), on AIX the symbols must
be explicitly exported.  In addition, when the shared library is
built it must be linked using a list of the available symbols.

This patch covers the changes need to:

 1) Export the symbols when building the node executable
 2) Generate the file listing the symbols that can be used when
    building the shared library.

For AIX, it breaks the build process into 2 steps.  The first builds
a static library and then generates a node.exp file which contains
the symbols from that library.  The second builds the node executable
and uses the node.exp file to specify which symbols should be
exported.  In addition, it save the node.exp file so that it can
later be used in the creation of the shared library when building
a native module.

The following additional steps will be required in dependent projects
to fully enable AIX for native modules and are being worked
separately:

 - Updates to node-gyp to use node.exp when creating the
   shared library for a native module
 - Fixes to gyp related to copying files as covered in
      https://codereview.chromium.org/1368133002/patch/1/10001
 - Pulling in updated gyp versions to Node and node-gyp
 - Pulling latest libuv

These changes were done to minimize the change to other platforms
by working within the existing structure to add the 2 step process
for AIX without changing the process for other platforms.

Author: mhdawson

configure

@@ -657,6 +657,10 @@ def configure_node(o):
   elif target_arch in ('mips', 'mipsel'):
     configure_mips(o)
 
+  if flavor == 'aix':
+    o['variables']['node_core_target_name'] = 'node_base'
+    o['variables']['node_target_type'] = 'static_library'
+
   if flavor in ('solaris', 'mac', 'linux', 'freebsd'):
     use_dtrace = not options.without_dtrace
     # Don't enable by default on linux and freebsd

node.gyp

@@ -13,6 +13,7 @@
     'node_shared_openssl%': 'false',
     'node_v8_options%': '',
     'node_target_type%': 'executable',
+    'node_core_target_name%': 'node',
     'library_files': [
       'src/node.js',
       'lib/_debug_agent.js',
@@ -79,7 +80,7 @@
 
   'targets': [
     {
-      'target_name': 'node',
+      'target_name': '<(node_core_target_name)',
       'type': '<(node_target_type)',
 
       'dependencies': [
@@ -666,5 +667,53 @@
         'test/cctest/util.cc',
       ],
     }
-  ] # end targets
+  ], # end targets
+
+  'conditions': [
+    ['OS=="aix"', {
+      'targets': [
+        {
+          'target_name': 'node',
+          'type': 'executable',
+          'dependencies': ['<(node_core_target_name)', 'node_exp'],
+
+          'include_dirs': [
+            'src',
+            'deps/v8/include',
+          ],
+
+          'sources': [
+            'src/node_main.cc',
+            '<@(library_files)',
+            # node.gyp is added to the project by default.
+            'common.gypi',
+          ],
+
+          'ldflags': ['-Wl,-bbigtoc,-bE:<(PRODUCT_DIR)/node.exp'],
+        },
+        {
+          'target_name': 'node_exp',
+          'type': 'none',
+          'dependencies': [
+            '<(node_core_target_name)',
+          ],
+          'actions': [
+            {
+              'action_name': 'expfile',
+              'inputs': [
+                '<(OBJ_DIR)'
+              ],
+              'outputs': [
+                '<(PRODUCT_DIR)/node.exp'
+              ],
+              'action': [
+                'sh', 'tools/create_expfile.sh',
+                      '<@(_inputs)', '<@(_outputs)'
+              ],
+            }
+          ]
+        }
+      ], # end targets
+    }], # end aix section
+  ], # end conditions block
 }

tools/create_expfile.sh

@@ -0,0 +1,48 @@
+#!/bin/sh
+# This script writes out all the exported symbols to a file
+# AIX needs this as sybmols are not exported by an
+# executable by default and we need to list
+# them specifically in order to export them
+# so that they can be used by native add-ons
+#
+# The raw symbol data is objtained by using nm on
+# the .a files which make up the node executable
+#
+# -Xany makes sure we get symbols on both
+# 32 bit and 64 bit as by default we'd only get those
+# for 32 bit
+#
+# -g selects only exported symbols
+#
+# -C, -B and -p ensure the output is in a format we
+# can easily parse and convert into the symbol we need
+#
+# -C suppresses the demangling of C++ names
+# -B gives us output in BSD format
+# -p displays the info in a standard portable output format
+#
+# We only include symbols if they are of the
+# following types and don't start with a dot.
+#
+# T - Global text symbol
+# D - Global data symbol
+# B - Gobal bss symbol.
+#
+# the final sort allows us to remove any duplicates
+#
+# We need to exclude gtest libraries as they are not
+# linked into the node executable
+#
+echo "Searching $1 to write out expfile to $2"
+
+# this special sequence must be at the start of the exp file
+echo "#!." > $2
+
+# pull the symbols from the .a files
+find $1 -name "*.a" | grep -v gtest \
+  | xargs nm -Xany -BCpg \
+  | awk '{
+      if ((($2 == "T") || ($2 == "D") || ($2 == "B")) &&
+          (substr($3,1,1) != ".")) { print $3 }
+    }' \
+  | sort -u >> $2

tools/install.py

@@ -160,6 +160,10 @@ def headers(action):
     'src/node_version.h',
   ], 'include/node/')
 
+  # Add the expfile that is created on AIX
+  if sys.platform.startswith('aix'):
+    action(['out/Release/node.exp'], 'include/node/')
+
   subdir_files('deps/cares/include', 'include/node/', action)
   subdir_files('deps/v8/include', 'include/node/', action)