--- a/build/moz.configure/init.configure
+++ b/build/moz.configure/init.configure
@@ -363,16 +363,18 @@ def split_triplet(triplet):
     elif os.startswith('dragonfly'):
         canonical_os = canonical_kernel = 'DragonFly'
     elif os.startswith('freebsd'):
         canonical_os = canonical_kernel = 'FreeBSD'
     elif os.startswith('netbsd'):
         canonical_os = canonical_kernel = 'NetBSD'
     elif os.startswith('openbsd'):
         canonical_os = canonical_kernel = 'OpenBSD'
+    elif os.startswith('solaris'):
+        canonical_os = canonical_kernel = 'SunOS'
     else:
         die('Unknown OS: %s' % os)
 
     # The CPU granularity is probably not enough. Moving more things from
     # old-configure will tell us if we need more
     if cpu.endswith('86') or (cpu.startswith('i') and '86' in cpu):
         canonical_cpu = 'x86'
         endianness = 'little'
@@ -621,16 +623,23 @@ set_define('XP_MACOSX', target_is_osx)
 
 @depends(target)
 def target_is_linux(target):
     if target.kernel == 'Linux':
         return True
 
 set_define('XP_LINUX', target_is_linux)
 
+@depends(target)
+def target_is_solaris(target):
+    if target.kernel == 'SunOS':
+        return True
+
+set_define('XP_SOLARIS', target_is_solaris)
+
 # The application/project to build
 # ==============================================================
 option('--enable-application', nargs=1, env='MOZ_BUILD_APP',
        help='Application to build. Same as --enable-project.')
 
 @depends('--enable-application', '--help')
 def application(app, help):
     if app:

--- a/ipc/chromium/chromium-config.mozbuild
+++ b/ipc/chromium/chromium-config.mozbuild
@@ -35,16 +35,19 @@ if CONFIG['OS_ARCH'] == 'WINNT':
         DEFINES['COMPILER_MSVC'] = True
 
 else:
     DEFINES['OS_POSIX'] = 1
 
     if CONFIG['OS_ARCH'] == 'Darwin':
         DEFINES['OS_MACOSX'] = 1
 
+    elif CONFIG['OS_ARCH'] == 'SunOS':
+        DEFINES['OS_SOLARIS'] = 1
+
     elif CONFIG['OS_ARCH'] == 'DragonFly':
         DEFINES.update({
             'OS_DRAGONFLY': 1,
             'OS_BSD': 1,
         })
 
     elif CONFIG['OS_ARCH'] == 'FreeBSD' or CONFIG['OS_ARCH'] == 'GNU_kFreeBSD':
         DEFINES.update({

--- a/ipc/chromium/src/build/build_config.h
+++ b/ipc/chromium/src/build/build_config.h
@@ -27,32 +27,34 @@
 #elif defined(__DragonFly__)
 #define OS_DRAGONFLY 1
 #elif defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
 #define OS_FREEBSD 1
 #elif defined(__NetBSD__)
 #define OS_NETBSD 1
 #elif defined(__OpenBSD__)
 #define OS_OPENBSD 1
+#elif defined(__sun__)
+#define OS_SOLARIS 1
 #elif defined(_WIN32)
 #define OS_WIN 1
 #else
 #error Please add support for your platform in build/build_config.h
 #endif
 
 // For access to standard BSD features, use OS_BSD instead of a
 // more specific macro.
 #if defined(OS_DRAGONFLY) || defined(OS_FREEBSD)	\
   || defined(OS_NETBSD) || defined(OS_OPENBSD)
 #define OS_BSD 1
 #endif
 
 // For access to standard POSIX features, use OS_POSIX instead of a more
 // specific macro.
-#if defined(OS_MACOSX) || defined(OS_LINUX) || defined(OS_BSD)
+#if defined(OS_MACOSX) || defined(OS_LINUX) || defined(OS_BSD) || defined(OS_SOLARIS)
 #define OS_POSIX 1
 #endif
 
 // Compiler detection.
 #if defined(__GNUC__)
 #define COMPILER_GCC 1
 #elif defined(_MSC_VER)
 #define COMPILER_MSVC 1

--- a/python/mozbuild/mozbuild/configure/constants.py
+++ b/python/mozbuild/mozbuild/configure/constants.py
@@ -19,27 +19,29 @@ OS = EnumString.subclass(
     'Android',
     'DragonFly',
     'FreeBSD',
     'GNU',
     'iOS',
     'NetBSD',
     'OpenBSD',
     'OSX',
+    'SunOS',
     'WINNT',
 )
 
 Kernel = EnumString.subclass(
     'Darwin',
     'DragonFly',
     'FreeBSD',
     'kFreeBSD',
     'Linux',
     'NetBSD',
     'OpenBSD',
+    'SunOS',
     'WINNT',
 )
 
 CPU_bitness = {
     'aarch64': 64,
     'Alpha': 64,
     'arm': 32,
     'hppa': 32,
@@ -94,12 +96,13 @@ assert sorted(CPU_preprocessor_checks.ke
 kernel_preprocessor_checks = {
     'Darwin': '__APPLE__',
     'DragonFly': '__DragonFly__',
     'FreeBSD': '__FreeBSD__',
     'kFreeBSD': '__FreeBSD_kernel__',
     'Linux': '__linux__',
     'NetBSD': '__NetBSD__',
     'OpenBSD': '__OpenBSD__',
+    'SunOS': '__sun__',
     'WINNT': '_WIN32 || __CYGWIN__',
 }
 
 assert sorted(kernel_preprocessor_checks.keys()) == sorted(Kernel.POSSIBLE_VALUES)

--- a/toolkit/crashreporter/moz.build
+++ b/toolkit/crashreporter/moz.build
@@ -83,20 +83,16 @@ if CONFIG['OS_TARGET'] == 'Android':
     DEFINES['ANDROID_PACKAGE_NAME'] = '"%s"' % CONFIG['ANDROID_PACKAGE_NAME']
     # NDK5 workarounds
     DEFINES['_STLP_CONST_CONSTRUCTOR_BUG'] = True
     DEFINES['_STLP_NO_MEMBER_TEMPLATES'] = True
     LOCAL_INCLUDES += [
         '/toolkit/crashreporter/google-breakpad/src/common/android/include',
     ]
 
-if CONFIG['OS_ARCH'] == 'SunOS':
-    # there's no define for this normally
-    DEFINES['XP_SOLARIS'] = True
-
 DEFINES['UNICODE'] = True
 DEFINES['_UNICODE'] = True
 
 JAR_MANIFESTS += ['jar.mn']
 
 LOCAL_INCLUDES += [
     'google-breakpad/src',
 ]

--- a/xpcom/ds/nsMathUtils.h
+++ b/xpcom/ds/nsMathUtils.h
@@ -6,17 +6,17 @@
 
 #ifndef nsMathUtils_h__
 #define nsMathUtils_h__
 
 #include "nscore.h"
 #include <cmath>
 #include <float.h>
 
-#ifdef SOLARIS
+#if defined(XP_SOLARIS)
 #include <ieeefp.h>
 #endif
 
 /*
  * round
  */
 inline double
 NS_round(double aNum)