From 30b29d8f8745263475d67576c4b81ff164482676 Mon Sep 17 00:00:00 2001
From: Ben Noordhuis <info@bnoordhuis.nl>
Date: Fri, 2 Mar 2012 02:14:27 +0100
Subject: [PATCH] build: disable -fstrict-aliasing if gcc < 4.6.0

A compiler bug in older versions of gcc makes it do unsafe optimizations at -O1
and higher. This manifested itself with (at least) gcc 4.5.2 on SmartOS because
it made V8 hang in a busy loop.

See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45883
---
 common.gypi | 17 ++++++++---------
 configure   | 31 +++++++++++++++++++------------
 2 files changed, 27 insertions(+), 21 deletions(-)

diff --git a/common.gypi b/common.gypi
index 699230ac337..6e13b6091ad 100644
--- a/common.gypi
+++ b/common.gypi
@@ -1,5 +1,6 @@
 {
   'variables': {
+    'strict_aliasing%': 'false',     # turn on/off -fstrict-aliasing
     'visibility%': 'hidden',         # V8's visibility setting
     'target_arch%': 'ia32',          # set v8's target architecture
     'host_arch%': 'ia32',            # set v8's host architecture
@@ -34,19 +35,17 @@
         },
       },
       'Release': {
+        'cflags': [ '-O3', '-fdata-sections', '-ffunction-sections' ],
         'conditions': [
-          [ 'OS!="solaris"', {
-              'cflags': [ '-O3','-fomit-frame-pointer', '-fdata-sections', '-ffunction-sections' ],
-          }],
-          [ 'OS=="solaris" and gcc_optimize_level =="-O3"', {
-              'cflags': [ '-O3', '-fdata-sections', '-ffunction-sections' ],	
-          }],
-          [ 'OS=="solaris" and gcc_optimize_level =="-O"', {
-              'cflags': [ '-O', '-fdata-sections', '-ffunction-sections' ], # For bug fix of #2830	
-          }],
           ['target_arch=="x64"', {
             'msvs_configuration_platform': 'x64',
           }],
+          ['OS=="solaris"', {
+            'cflags': [ '-fno-omit-frame-pointer' ],
+          }],
+          ['strict_aliasing!="true"', {
+            'cflags': [ '-fno-strict-aliasing' ],
+          }],
         ],
         'msvs_settings': {
           'VCCLCompilerTool': {
diff --git a/configure b/configure
index 0b5254e1b2b..42ea12e9cb8 100755
--- a/configure
+++ b/configure
@@ -2,6 +2,7 @@
 import optparse
 import os
 import pprint
+import re
 import subprocess
 import sys
 from distutils.version import StrictVersion
@@ -185,17 +186,17 @@ def host_arch():
 def target_arch():
   return host_arch()
 
-def gcc_optimize_level():
-  cc = ['gcc']
-  cmd = cc + [ '-dumpversion' ]
-  p = subprocess.Popen(cmd, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-  p.stdin.write('\n')
-  out = p.communicate()[0]
-  gcc_version = (str(out).split('\n'))[0]
-  if StrictVersion(gcc_version) >= '4.6.1':
-    return '-O3'
-  else:
-    return '-O'
+
+def gcc_version():
+  try:
+    proc = subprocess.Popen('gcc -v'.split(), stderr=subprocess.PIPE)
+  except OSError:
+    return None
+  version = proc.communicate()[1].split('\n')[-2]
+  match = re.match('gcc version (\d+)\.(\d+)\.(\d+)', version)
+  assert match, 'Failed to parse gcc version `%s`' % version
+  return ['LLVM' in version] + map(int, match.groups())
+
 
 def configure_node(o):
   # TODO add gdb
@@ -207,10 +208,16 @@ def configure_node(o):
   o['variables']['target_arch'] = options.dest_cpu or target_arch()
   o['default_configuration'] = 'Debug' if options.debug else 'Release'
 
+  # turn off strict aliasing if gcc < 4.6.0 unless it's llvm-gcc
+  # see http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45883
+  # see http://code.google.com/p/v8/issues/detail?id=884
+  # TODO handle CC=clang
+  o['variables']['strict_aliasing'] = b(gcc_version() >= (False, 4, 6, 0))
+
   # TODO move to node.gyp
   if sys.platform == 'sunos5':
     o['variables']['visibility'] = '' # FIXME -fvisibility=hidden, should be a gcc check
-    o['variables']['gcc_optimize_level'] = gcc_optimize_level() # For bug fix of #2830
+
 
 def configure_libz(o):
   o['variables']['node_shared_zlib'] = b(options.shared_zlib)