Looking at
http://clang.llvm.org/doxygen/CXString_8h_source.html
it seems that CXString as returned by clang_getCursorSpelling() is not
a pointer:
typedef struct {
const void *data;
unsigned private_flags;
} CXString;
If that's right, I'm a little surprised that `cursor-spelling` works
--- but when you get representation wrong, strange things can happen,
including something working when it shouldn't.
Am I looking at the right library/definitions?
At Sun, 28 Sep 2014 10:48:06 -0700, Eric Dobson wrote:
> I'm trying to debug an FFI crash that I'm seeing, and because it is
> dealing with C code the error just presents as a segfault. I believe I
> have tracked down what is causing the problem, but don't understand
> how it could be doing so.
>
> I have two racket functions which take a "cursor" (the foreign
> libraries object) and return a string representation of it, which I'm
> trying to use for debugging.
>
> (define raw-clang-get-cstring
> (get-ffi-obj "clang_getCString" lib-clang
> (_fun _pointer -> _string)))
>
> (define raw-cursor-spelling
> (get-ffi-obj "clang_getCursorSpelling" lib-clang
> (_fun _CXCursor -> _pointer)))
>
> (define (cursor-spelling c)
> (raw-clang-get-cstring (raw-cursor-spelling c)))
>
> (define cursor-spelling2
> (get-ffi-obj "clang_getCursorSpelling" lib-clang
> (_fun _CXCursor -> (make-ctype _pointer values (λ (v)
> (raw-clang-get-cstring v))))))
>
> If I use cursor-spelling, I have not been able to trigger a crash. But
> if I use cursor-spelling2 I can reliably trigger a crash.
>
> Is there anything obvious on how these functions are different?
> Because they look to me like they should be doing the same thing. If
> it would be helpful I can try to get my code in a portable enough
> shape so that it will work/crash on another machine.
>
> ____________________
> Racket Users list:
> http://lists.racket-lang.org/users
____________________
Racket Users list:
http://lists.racket-lang.org/users
