Fix for building ARM/linux using clang.

src/include/concurrency_ops.h

 /*
  * Copyright (c) 2012 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef NATIVE_CLIENT_SRC_INCLUDE_CONCURRENCY_OPS_H_
 #define NATIVE_CLIENT_SRC_INCLUDE_CONCURRENCY_OPS_H_ 1
 
@@ skipping 70 matching lines @@
    *     We need to do this for writable_addr.
    *  2) It clears the instruction cache for the address range.
    *     We need to do this for executable_addr.
    *
    * We do not need apply (1) to executable_addr or apply (2) to
    * writable_addr, but the Linux kernel does not expose (1) and (2)
    * as separate operations; it just provides a single syscall that
    * does both.  For background, see:
    * http://code.google.com/p/nativeclient/issues/detail?id=2443
    */
-  __builtin___clear_cache(writable_addr, writable_addr + size);
-  __builtin___clear_cache(executable_addr, executable_addr + size);
+  __builtin___clear_cache((char*)writable_addr, (char*)writable_addr + size);

[Mark Seaborn, 2014/07/23 19:13:41]

What version of Clang did you test against?

It looks like Clang has been fixed to use void* and so match GCC:
http://llvm.org/viewvc/llvm-project?view=revision&revision=181810

[Sam Clegg, 2014/07/23 19:21:52]

clang is coming from the chrome tree: third_party/llvm-build/Release+Asserts

I assume its very recent.

[Mark Seaborn, 2014/07/24 18:45:35]

Ah, the issue is that __clear_cache() and __builtin___clear_cache() have
different types:

include/clang/Basic/Builtins.def:BUILTIN(__builtin___clear_cache, "vc*c*", "n")
include/clang/Basic/BuiltinsARM.def:BUILTIN(__clear_cache, "vv*v*", "i")

It should be OK to change this to use __clear_cache() instead.  Aside from the
type, they appear to behave the same on both GCC and Clang.  They both call
libgcc's __clear_cache().

Can you do a standalone change to change this part?

+  __builtin___clear_cache((char*)executable_addr,
+                          (char*)executable_addr + size);
 #else
   /*
    * Give an error in case we ever target a non-gcc compiler for ARM
    * or for some other architecture that we might support in the
    * future.
    */
 # error "Don't know how to clear the icache on this architecture"
 #endif
 }
 
 
 #endif  /* NATIVE_CLIENT_SRC_INCLUDE_CONCURRENCY_OPS_H_ */