bug#13342: [PARTIALLY SOLVED] bug#13342: Errors trying to build Guile 2.0.7
Hi Ludo:
I think the reason that we get this error is that the "a" argument is declared
to be only 8 bits wide
but is passed in as -1 which is correctly represented as 0x
However an 8-bit representation is 0xFF which is only 255.
Here is how I tracked it down:
(0) Took the printf's from my test program and placed them in
scm_t_int64 test_ffi_sum (scm_t_int8 a, scm_t_int16 b,
scm_t_int32 c, scm_t_int64 d);
scm_t_int64 test_ffi_sum (scm_t_int8 a, scm_t_int16 b,
scm_t_int32 c, scm_t_int64 d)
{
scm_t_int64 sum;
printf("scm_t_int64 d %" "ll" "d" " %#llX \n", d,d);
printf("scm_t_int32 c %" "d" " %#X \n", c,c);
printf("scm_t_int16 b %" "hd" " %#X \n", b,b);
printf("scm_t_int8 a %" "hh" "d" " %#X \n", a,a);
sum = d + c + b + a;
printf("scm_t_int64 sum %" "ll" "d" " %#llX \n", sum,sum);
a = -1; // NOTE:re-assign of a
printf("scm_t_int16 a %" "hd" " %#X \n", a,a);
return d + c + b + a;
}
(1) Did make and make check with the following result
scm_t_int64 d 400 0X9502F9000
scm_t_int32 c -3 0X8AD0
scm_t_int16 b 2000 0X7D0
scm_t_int8 a -1 0XFF
scm_t_int64 sum 3972255 0X9502F239F
scm_t_int16 a -1 0X
PASS: test-ffi
(2) Observe that the test passed.
So I think my original suspicion seems to have been confirmed.
I do not know where to go from here but await your further instructions.
respect
Peter
bug#13386: Fwd: bug#13342: Errors trying to build Guile 2.0.7
Begin forwarded message:
> From: Peter Teeson
> Subject: Re: bug#13342: Errors trying to build Guile 2.0.7
> Date: 7 January, 2013 8:21:59 PM EST
> To: Ludovic Courtès
>
> Hi Ludo:
>
> On 2013-01-04, at 12:23 PM, Ludovic Courtès wrote:
> bad return from expression `(f-sum -1 2000 -3 400)': expected
> 3971999; got 3972255
> 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 3972255 - 3971999 = 256!
>
> (2) This program
> //
> // main.c
> // testffi
> //
> // Created by Peter Teeson on 13-01-07.
> // Copyright (c) 2013 PHT Software. All rights reserved.
> //
>
> #include
> #include
>
> 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, -3, 400);
> return 0;
> }
>
> (3) produces this output
>
> int64 d 400 0X9502F9000
> int32 c -3 0X8AD0
> int16 b 2000 0X7D0
> int08 a -1 0X
> int64 sum 3971999 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 -3 400)
> (+ -1 2000 -3 400))
>
> might be the culprit and I am guessing that it is this expression
>
> (+ -1 2000 -3 400)
>
> 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
bug#13342: Errors trying to build Guile 2.0.7 [PARTIALLY SOLVED]
Hi Ludo:
I believe my conjecture that -1 was correct based on the following:
(0) I took the printf statements from my test program and placed them in
test-ffi-sum:
scm_t_int64 test_ffi_sum (scm_t_int8 a, scm_t_int16 b,
scm_t_int32 c, scm_t_int64 d);
scm_t_int64 test_ffi_sum (scm_t_int8 a, scm_t_int16 b,
scm_t_int32 c, scm_t_int64 d)
{
scm_t_int64 sum;
printf("scm_t_int64 d %" "ll" "d" " %#llX \n", d,d);
printf("scm_t_int32 c %" "d" " %#X \n", c,c);
printf("scm_t_int16 b %" "hd" " %#X \n", b,b);
printf("scm_t_int8 a %" "hh" "d" " %#X \n", a,a);
sum = d + c + b + a;
printf("scm_t_int64 sum %" "ll" "d" " %#llX \n", sum,sum);
a = -1; // NOTE re-assinging of a!
printf("scm_t_int16 a %" "hd" " %#X \n", a,a);
return d + c + b + a;
}
(1) Ran make
Making all in standalone
make all-am
CC libtest_ffi_la-test-ffi-lib.lo
CCLD libtest-ffi.la
and then make check
scm_t_int64 d 400 0X9502F9000
scm_t_int32 c -3 0X8AD0
scm_t_int16 b 2000 0X7D0
scm_t_int8 a -1 0XFF
scm_t_int64 sum 3972255 0X9502F239F
scm_t_int16 a -1 0X
PASS: test-ffi
(2) Since scm_t_int8 is only 8 bits wide it's maximum value is 0xFF <=> 255
Reassigning "a" to be -1 allowed it to pass the test.
(3) Therefore I conclude that this is why the test fails (correctly IMHO).
You can only get a litre of milk into a litre jar!
(4) Where do we go from here?
respect
Peter
