[cffi-devel] Re: usage question

[Bruce Butterfield]

Still having a problem and I think it's related to the allocation of the 
buffer. Here is C code that works fine:

(BTW, I'm running SBCL 0.9.5, cffi-luis-051002-1333, on Ubuntu Hoary/x86)

=================================
typedef struct
{
     unsigned char* bp;
     unsigned int size;
     unsigned int allocated;
     unsigned int next;
} TidyBuffer;

typedef void* TidyDoc;

TidyDoc tidyCreate(void);
int tidyParseString(TidyDoc tdoc, const char* str);
int tidySaveBuffer(TidyDoc tdoc, TidyBuffer* buf);

int main(int argc, char **argv )
{
   const char* input = "<title>Foo</title><p>Foo!";
   TidyBuffer output = {0};

   TidyDoc tdoc = tidyCreate();
   tidyParseString( tdoc, input );           // Parse the input
   tidySaveBuffer( tdoc, &output );          // Pretty Print

   printf( "\n%s\n", output.bp );
}

===========================

and my lisp equivalent:

;;;;;;;;;;;;;;;;;;;;;;;
(cffi:load-foreign-library "/usr/lib/libtidy.so")

(cffi:defcstruct tidy-buffer
   (bp :pointer)
   (size :unsigned-int)
   (allocated :unsigned-int)
   (next :unsigned-int))

(cffi:defcfun ("tidyCreate" tidy-create) :pointer)

(cffi:defcfun ("tidyParseString" tidy-parse-string) :int
   (doc :pointer)
   (input :pointer))

(cffi:defcfun ("tidySaveBuffer" tidy-save-buffer) :int
   (doc :pointer)
   (output tidy-buffer))

(defun tidy-string (str)
   (cffi:with-foreign-object (output tidy-buffer)
	(let ((tdoc (tidy-create)))
	  (cffi:with-foreign-string (s str)
		(tidy-parse-string tdoc s)
		(tidy-save-buffer tdoc output)))))

(tidy-string "<title>Foo</title><p>Foo!")
;;;;;;;;;;;;;;;;;;;;;;;;

when it gets to the call to tidy-save-buffer I get a stack trace:

memory fault
    [Condition of type SB-KERNEL::MEMORY-FAULT-ERROR]

Restarts:
   0: [ABORT] Abort SLIME compilation.
   1: [ABORT-REQUEST] Abort handling SLIME request.
   2: [TERMINATE-THREAD] Terminate this thread (#<THREAD "worker" 
{9E2F069}>)

Backtrace:
   0: (SB-KERNEL::MEMORY-FAULT-ERROR)
   1: ("foreign function: call_into_lisp")
   2: ("foreign function: post_signal_tramp")
   3: ("foreign function: tidyBufPutByte")
   4: ("foreign function: #xB5EF69F7")
   5: ("foreign function: tidyPutByte")
   6: ("foreign function: #xB5EF8359")
   7: ("foreign function: WriteChar")
   8: ("foreign function: PFlushLine")
   9: ("foreign function: PPrintTree")
  10: ("foreign function: PPrintTree")
  11: ("foreign function: tidyDocSaveStream")
  12: ("foreign function: tidyDocSaveBuffer")
  13: ("foreign function: tidySaveBuffer")
  14: (TIDY-SAVE-BUFFER #.(SB-SYS:INT-SAP #X0827B590) #.(SB-SYS:INT-SAP 
#XB5A3DFEC))
  15: (TIDY-STRING "<title>Foo</title><p>Foo!")
  16: ((SB-PCL::FAST-METHOD SWANK-BACKEND:SWANK-COMPILE-STRING (T)) 
#<unused argument> #<unused argument> "(tidy-string 
\"<title>Foo</title><p>Foo!\")
" (:BUFFER "tinytidy.lisp" :POSITION 624 :DIRECTORY "/home/bruce/src/cl/"))