Support for building Chrome using Clang.

To build, set the clang=1 gyp_define.

This patch is the culmination of many months of effort and many
patches.  It contains the minimal changes to Chrome that
are Clang-specific.

With this, I can build the "chrome" target.  Once this patch
is in, we can incrementally fix bits of Chrome and various
tests and remove the Clang-specific workarounds.

Review URL: http://codereview.chromium.org/522020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@59882 0039d316-1c4b-4281-b951-d872f2087c98

8 files changed, 62 insertions, 7 deletions

diff --git a/base/linked_list.h b/base/linked_list.h
index 0626025..d91a1f8 100644
--- a/base/linked_list.h
+++ b/base/linked_list.h
@@ -126,6 +126,13 @@ class LinkNode {
     return static_cast<T*>(this);
   }
 
+  // Work around a Clang bug reported upstream:
+  //   http://llvm.org/bugs/show_bug.cgi?id=7974
+  // TODO(evanm): remove this and its sole caller.
+  void set(LinkNode<T>* prev, LinkNode<T>* next) {
+    previous_ = prev; next_ = next;
+  }
+
  private:
   LinkNode<T>* previous_;
   LinkNode<T>* next_;
@@ -137,7 +144,7 @@ class LinkedList {
   // The "root" node is self-referential, and forms the basis of a circular
   // list (root_.next() will point back to the start of the list,
   // and root_->previous() wraps around to the end of the list).
-  LinkedList() : root_(&root_, &root_) {}
+  LinkedList() { root_.set(&root_, &root_); }
 
   // Appends |e| to the end of the linked list.
   void Append(LinkNode<T>* e) {
diff --git a/build/common.gypi b/build/common.gypi
index 0f721ed..d81c567 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -251,6 +251,12 @@
     # Set this to true to enable SELinux support.
     'selinux%': 0,
 
+    # Set this to true when building with Clang.
+    # See http://code.google.com/p/chromium/wiki/Clang for details.
+    # TODO: eventually clang should behave identically to gcc, and this
+    # won't be necessary.
+    'clang%': 0,
+
     # Override whether we should use Breakpad on Linux. I.e. for Chrome bot.
     'linux_breakpad%': 0,
     # And if we want to dump symbols for Breakpad-enabled builds.
@@ -1114,6 +1120,23 @@
                 ],
               }]]
           }],
+          ['clang==1', {
+            'cflags': [
+              # Don't warn about unused variables, due to a common pattern:
+              #   scoped_deleter unused_variable(&thing_to_delete);
+              '-Wno-unused-variable',
+              # Clang spots more unused functions.
+              '-Wno-unused-function',
+              # gtest confuses clang.
+              '-Wno-bool-conversions',
+              # Don't die on dtoa code that uses a char as an array index.
+              '-Wno-char-subscripts',
+            ],
+            'cflags!': [
+              # Clang doesn't seem to know know this flag.
+              '-mfpmath=sse',
+            ],
+          }],
           ['no_strict_aliasing==1', {
             'cflags': [
               '-fno-strict-aliasing',
diff --git a/chrome/browser/zygote_main_linux.cc b/chrome/browser/zygote_main_linux.cc
index 20b0352..b4dd7be 100644
--- a/chrome/browser/zygote_main_linux.cc
+++ b/chrome/browser/zygote_main_linux.cc
@@ -50,9 +50,10 @@
 
 #include "unicode/timezone.h"
 
-#if defined(ARCH_CPU_X86_FAMILY) && !defined(CHROMIUM_SELINUX)
+#if defined(ARCH_CPU_X86_FAMILY) && !defined(CHROMIUM_SELINUX) && \
+    !defined(__clang__)
 // The seccomp sandbox is enabled on all ia32 and x86-64 processor as long as
-// we aren't using SELinux.
+// we aren't using SELinux or clang.
 #define SECCOMP_SANDBOX
 #endif
 
diff --git a/chrome/nacl/nacl_main_platform_delegate_linux.cc b/chrome/nacl/nacl_main_platform_delegate_linux.cc
index 0932c08..9e3acef 100644
--- a/chrome/nacl/nacl_main_platform_delegate_linux.cc
+++ b/chrome/nacl/nacl_main_platform_delegate_linux.cc
@@ -34,7 +34,8 @@ void NaClMainPlatformDelegate::EnableSandbox() {
   //
   // The seccomp sandbox is started in the renderer.
   // http://code.google.com/p/seccompsandbox/
-#if defined(ARCH_CPU_X86_FAMILY) && !defined(CHROMIUM_SELINUX)
+#if defined(ARCH_CPU_X86_FAMILY) && !defined(CHROMIUM_SELINUX) && \
+    !defined(__clang__)
   // N.b. SupportsSeccompSandbox() returns a cached result, as we already
   // called it earlier in the zygote. Thus, it is OK for us to not pass in
   // a file descriptor for "/proc".
diff --git a/chrome/renderer/renderer_main_platform_delegate_linux.cc b/chrome/renderer/renderer_main_platform_delegate_linux.cc
index a965ede..ad43330 100644
--- a/chrome/renderer/renderer_main_platform_delegate_linux.cc
+++ b/chrome/renderer/renderer_main_platform_delegate_linux.cc
@@ -36,7 +36,8 @@ bool RendererMainPlatformDelegate::EnableSandbox() {
   //
   // The seccomp sandbox is started in the renderer.
   // http://code.google.com/p/seccompsandbox/
-#if defined(ARCH_CPU_X86_FAMILY) && !defined(CHROMIUM_SELINUX)
+#if defined(ARCH_CPU_X86_FAMILY) && !defined(CHROMIUM_SELINUX) && \
+    !defined(__clang__)
   // N.b. SupportsSeccompSandbox() returns a cached result, as we already
   // called it earlier in the zygote. Thus, it is OK for us to not pass in
   // a file descriptor for "/proc".
diff --git a/sandbox/sandbox.gyp b/sandbox/sandbox.gyp
index 1150261..692e526 100644
--- a/sandbox/sandbox.gyp
+++ b/sandbox/sandbox.gyp
@@ -135,7 +135,7 @@
         },
       ],
     }],
-    [ 'OS=="linux" and selinux==0', {
+    [ 'OS=="linux" and selinux==0 and clang==0', {
       'targets': [
         {
           'target_name': 'chrome_sandbox',
@@ -168,7 +168,7 @@
         },
       ],
     }],
-    [ 'OS=="linux" and selinux==1', {
+    [ 'OS=="linux" and (selinux==1 or clang==1)', {
       # GYP requires that each file have at least one target defined.
       'targets': [
         {
diff --git a/skia/skia.gyp b/skia/skia.gyp
index c627925..20e593d 100644
--- a/skia/skia.gyp
+++ b/skia/skia.gyp
@@ -592,6 +592,14 @@
             '../third_party/skia/src/opts/opts_check_SSE2.cpp'
           ],
         }],
+        ['clang==1', {
+          'defines': [
+            # Remove all use of __restrict__ -- skia uses it incorrectly,
+            # and clang is more strict about it.
+            # http://code.google.com/p/skia/issues/detail?id=63
+            'SK_RESTRICT=',
+          ],
+        }],
         [ 'OS == "linux" or OS == "freebsd" or OS == "openbsd" or OS == "solaris"', {
           'dependencies': [
             '../build/linux/system.gyp:gdk',
diff --git a/testing/gtest.gyp b/testing/gtest.gyp
index e813b49..da95f42 100644
--- a/testing/gtest.gyp
+++ b/testing/gtest.gyp
@@ -79,6 +79,20 @@
             ],
           },
         }],
+        ['clang==1', {
+          # We want gtest features that use tr1::tuple, but clang currently
+          # doesn't support the variadic templates used by libstdc++'s
+          # implementation.  gtest supports this scenario by providing its
+          # own implementation but we must opt in to it.
+          'defines': [
+            'GTEST_USE_OWN_TR1_TUPLE=1',
+          ],
+          'direct_dependent_settings': {
+            'defines': [
+              'GTEST_USE_OWN_TR1_TUPLE=1',
+            ],
+          },
+        }],
       ],
       'direct_dependent_settings': {
         'defines': [