Errors compiling using Clang

[jefvel]

I am trying to compile bullet using webidl with Clang, but I'm getting these errors:

/Users/jefvel/project/libs/bullet/src/bullet.cpp:35:21: error: pasting formed 'u"delete() is not allowed on const value."', an invalid preprocessing token
        if( !r->finalize ) hl_error("delete() is not allowed on const value.");
                           ^
/Users/jefvel/project/libs/bullet/../../hashlink/src/hl.h:586:55: note: expanded from macro 'hl_error'
#define hl_error(msg, ...) hl_throw(hl_alloc_strbytes(USTR(msg), ## __VA_ARGS__))
                                                      ^
/Users/jefvel/project/libs/bullet/../../hashlink/src/hl.h:234:21: note: expanded from macro 'USTR'
#       define USTR(str)        u##str
                                 ^
/Users/jefvel/project/libs/bullet/src/bullet.cpp:35:21: error: use of undeclared identifier 'u'
/Users/jefvel/project/libs/bullet/../../hashlink/src/hl.h:586:55: note: expanded from macro 'hl_error'
#define hl_error(msg, ...) hl_throw(hl_alloc_strbytes(USTR(msg), ## __VA_ARGS__))
                                                      ^
/Users/jefvel/project/libs/bullet/../../hashlink/src/hl.h:234:20: note: expanded from macro 'USTR'
#       define USTR(str)        u##str
                                ^
/Users/jefvel/project/libs/bullet/../../hashlink/src/hl.h:234:20: note: expanded from macro 'u'
/Users/jefvel/project/libs/bullet/src/bullet.cpp:43:16: error: assigning to 'void *' from incompatible type 'void (*)(pref<btVector3> *)'
        r->finalize = finalize;
                      ^~~~~~~~
/Users/jefvel/project/libs/bullet/src/bullet.cpp:557:9: note: in instantiation of function template specialization '_alloc_ref<btVector3>' requested here
        return alloc_ref((new btVector3()),btVector3);
               ^
/Users/jefvel/project/libs/bullet/src/bullet.cpp:30:24: note: expanded from macro 'alloc_ref'
#define alloc_ref(r,t) _alloc_ref(r,finalize_##t)

...

(It continues with a lot more error: assigning to 'void *' from incompatible type ' X errors.)

I managed to circumvent this and successfully compile by using gcc and setting the flag -fpermissive, but I'm wondering if there could be some way to make it work in Clang directly.