build: allow linking against system c-ares

configure

@@ -151,6 +151,26 @@ parser.add_option("--shared-http-parser-libname",
     dest="shared_http_parser_libname",
     help="Alternative lib name to link to (default: 'http_parser')")
 
+parser.add_option("--shared-cares",
+    action="store_true",
+    dest="shared_cares",
+    help="Link to a shared cares DLL instead of static linking")
+
+parser.add_option("--shared-cares-includes",
+    action="store",
+    dest="shared_cares_includes",
+    help="Directory containing cares header files")
+
+parser.add_option("--shared-cares-libpath",
+    action="store",
+    dest="shared_cares_libpath",
+    help="A directory to search for the shared cares DLL")
+
+parser.add_option("--shared-cares-libname",
+    action="store",
+    dest="shared_cares_libname",
+    help="Alternative lib name to link to (default: 'cares')")
+
 parser.add_option("--with-dtrace",
     action="store_true",
     dest="with_dtrace",
@@ -456,6 +476,20 @@ def configure_http_parser(o):
         o['include_dirs'] += [options.shared_http_parser_includes]
 
 
+def configure_cares(o):
+    o['variables']['node_shared_cares'] = b(options.shared_cares)
+
+    # assume shared cares if one of these is set?
+    if options.shared_cares_libpath:
+        o['libraries'] += ['-L%s' % options.shared_cares_libpath]
+    if options.shared_cares_libname:
+        o['libraries'] += ['-l%s' % options.shared_cares_libname]
+    elif options.shared_cares:
+        o['libraries'] += ['-lcares']
+    if options.shared_cares_includes:
+        o['include_dirs'] += [options.shared_cares_includes]
+
+
 def configure_v8(o):
   o['variables']['v8_use_snapshot'] = b(not options.without_snapshot)
   o['variables']['node_shared_v8'] = b(options.shared_v8)
@@ -510,6 +544,7 @@ output = {
 configure_node(output)
 configure_libz(output)
 configure_http_parser(output)
+configure_cares(output)
 configure_v8(output)
 configure_openssl(output)
 

doc/api/process.markdown

@@ -299,6 +299,7 @@ An example of the possible output looks like:
        { host_arch: 'x64',
          node_install_npm: 'true',
          node_prefix: '',
+         node_shared_cares: 'false',
          node_shared_http_parser: 'false',
          node_shared_v8: 'false',
          node_shared_zlib: 'false',

node.gyp

@@ -9,6 +9,7 @@
     'node_shared_v8%': 'false',
     'node_shared_zlib%': 'false',
     'node_shared_http_parser%': 'false',
+    'node_shared_cares%': 'false',
     'node_use_openssl%': 'true',
     'node_use_systemtap%': 'false',
     'node_shared_openssl%': 'false',
@@ -59,7 +60,6 @@
       'type': 'executable',
 
       'dependencies': [
-        'deps/cares/cares.gyp:cares',
         'deps/uv/uv.gyp:libuv',
         'node_js2c#host',
       ],
@@ -205,6 +205,10 @@
           'dependencies': [ 'deps/http_parser/http_parser.gyp:http_parser' ],
         }],
 
+        [ 'node_shared_cares=="false"', {
+          'dependencies': [ 'deps/cares/cares.gyp:cares' ],
+        }],
+
         [ 'OS=="win"', {
           'sources': [
             'src/res/node.rc',