From: Peter Teeson <pteeson@me.com>

Subject: Re: bug#13342: Errors trying to build Guile 2.0.7

Date: 7 January, 2013 8:21:59 PM EST

To: Ludovic Courtès <ludo@gnu.org>

Hi Ludo:

On 2013-01-04, at 12:23 PM, Ludovic Courtès wrote:

bad return from expression `(f-sum -1 2000 -30000 40000000000)': expected 39999971999; got 39999972255

FAIL: test-ffi

This is a known issue when building Guile with LLVM/Clang:

http://bugs.gnu.org/10015

http://bugs.gnu.org/10681

It would be great if you could investigate.

Here is the result of my investigation - do you agree?

My hypothesis is that the scheme interpreter is not calculating the sum correctly based on the following:

(0) First observe this

"In Apple's version of GCC, both cc and gcc are actually symbolic links to the llvm-gcc compiler.  Similarly, c++ and g++ are links to llvm-g++."

(1) Also we note that 39999972255 - 39999971999 = 256!

(2) This program

//

//  main.c

//  testffi

//

//  Created by Peter Teeson on 13-01-07.

//  Copyright (c) 2013 PHT Software. All rights reserved.

//

#include <stdio.h>

#include <inttypes.h>

int64_t test_ffi_sum (int8_t a, int16_t b,

                          int32_t c, int64_t d);

int64_t test_ffi_sum (int8_t a, int16_t b,

                      int32_t c, int64_t d)

{

    printf("int64 d %" PRId64 " %#llX \n", d,d);

    printf("int32 c %" PRId32 " %#X \n", c,c);

    printf("int16 b %" PRId16 " %#X \n", b,b);

    printf("int08 a %" PRId8 " %#X \n", a,a);

    int64_t sum = d + c + b + a;

    printf("int64 sum %" PRId64 " %#llX \n", sum,sum);

    return sum;

}

int main(int argc, const char * argv[])

{

    test_ffi_sum(-1, 2000, -30000, 40000000000);

    return 0;

}

(3) produces this output

int64 d 40000000000 0X9502F9000 

int32 c -30000 0XFFFF8AD0 

int16 b 2000 0X7D0 

int08 a -1 0XFFFFFFFF 

int64 sum 39999971999 0X9502F229F 

(4) This function in  /guile-2.0.7/test-suite/standalone/test-ffi 

;;

;; Multiple int args of differing types

;;

(define f-sum

  (pointer->procedure int64 (dynamic-func "test_ffi_sum" lib)

                      (list int8 int16 int32 int64)))

(test (f-sum -1 2000 -30000 40000000000)

      (+ -1 2000 -30000 40000000000))

might be the culprit and I am guessing that it is this expression

(+ -1 2000 -30000 40000000000) 

which the scheme interpreter is calculating incorrectly. Probably related to -1;

Since I am not familiar with the scheme/guile language I can't go any further than this without help.

Let me know if I can do more.

respect…..

Peter