build: enable V8's shared read-only heap

It is what V8's build config does by default.

PR-URL: nodejs#42809
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>

configure.py

@@ -1458,6 +1458,7 @@ def configure_v8(o):
   o['variables']['v8_use_siphash'] = 0 if options.without_siphash else 1
   o['variables']['v8_enable_pointer_compression'] = 1 if options.enable_pointer_compression else 0
   o['variables']['v8_enable_31bit_smis_on_64bit_arch'] = 1 if options.enable_pointer_compression else 0
+  o['variables']['v8_enable_shared_ro_heap'] = 0 if options.enable_pointer_compression else 1
   o['variables']['v8_trace_maps'] = 1 if options.trace_maps else 0
   o['variables']['node_use_v8_platform'] = b(not options.without_v8_platform)
   o['variables']['node_use_bundled_v8'] = b(not options.without_bundled_v8)

test/parallel/test-worker-nearheaplimit-deadlock.js

@@ -1,3 +1,7 @@
+// Flags: --no-node-snapshot
+// With node snapshot the OOM can occur during the deserialization of the
+// context, so disable it since we want the OOM to occur during the creation of
+// the message port.
 'use strict';
 const common = require('../common');
 const assert = require('assert');
@@ -11,10 +15,6 @@ if (!process.env.HAS_STARTED_WORKER) {
       maxYoungGenerationSizeMb: 0,
       maxOldGenerationSizeMb: 0
     },
-    // With node snapshot the OOM can occur during the deserialization of
-    // the context, so disable it since we want the OOM to occur during
-    // the creation of the message port.
-    execArgv: [ ...process.execArgv, '--no-node-snapshot']
   };
 
   const worker = new Worker(__filename, opts);

tools/v8_gypfiles/features.gypi

@@ -179,6 +179,10 @@
     # Controls the threshold for on-heap/off-heap Typed Arrays.
     'v8_typed_array_max_size_in_heap%': 64,
 
+    # Enable sharing read-only space across isolates.
+    # Sets -DV8_SHARED_RO_HEAP.
+    'v8_enable_shared_ro_heap%': 0,
+
     # Enable lazy source positions by default.
     'v8_enable_lazy_source_positions%': 1,
 
@@ -396,6 +400,9 @@
       ['v8_use_siphash==1', {
         'defines': ['V8_USE_SIPHASH',],
       }],
+      ['v8_enable_shared_ro_heap==1', {
+        'defines': ['V8_SHARED_RO_HEAP',],
+      }],
       ['dcheck_always_on!=0', {
         'defines': ['DEBUG',],
       }],

tools/v8_gypfiles/v8.gyp

@@ -1757,6 +1757,7 @@
               'v8_enable_verify_csa=<(v8_enable_verify_csa)',
               'v8_enable_lite_mode=<(v8_enable_lite_mode)',
               'v8_enable_pointer_compression=<(v8_enable_pointer_compression)',
+              'v8_enable_shared_ro_heap=<(v8_enable_shared_ro_heap)',
               'v8_enable_webassembly=<(v8_enable_webassembly)',
               # Not available in gyp.
               'v8_control_flow_integrity=0',