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FFI: Return the right alignment for structures.

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* libguile/foreign.c (scm_alignof): Fix handling of structure alignment.
  Reported by Aidan Gauland <aidalgol@no8wireless.co.nz>.

* test-suite/tests/foreign.test ("structs")["alignof { int8, double,
  int8 }", "int8, { int8, double, int8 }, int16"]: New tests.
This commit is contained in:
Ludovic Courtès 2011-03-10 22:24:23 +01:00
parent dd36ce77cd
commit d82f8518b9
2 changed files with 30 additions and 2 deletions
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20
libguile/foreign.c
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@ -402,8 +402,24 @@ SCM_DEFINE (scm_alignof, "alignof", 1, 0, 0, (SCM type),
/* a pointer */
return scm_from_size_t (alignof (void*));
else if (scm_is_pair (type))
/* a struct, yo */
return scm_alignof (scm_car (type));
{
/* TYPE is a structure. Section 3-3 of the i386, x86_64, PowerPC,
and SPARC P.S. of the System V ABI all say: "Aggregates
(structures and arrays) and unions assume the alignment of
their most strictly aligned component." */
size_t max;
for (max = 0; scm_is_pair (type); type = SCM_CDR (type))
{
size_t align;
align = scm_to_size_t (scm_alignof (SCM_CAR (type)));
if (align > max)
max = align;
}
return scm_from_size_t (max);
}
else
scm_wrong_type_arg (FUNC_NAME, 1, type);
}

12
test-suite/tests/foreign.test
View file

@ -228,6 +228,11 @@
(>= (sizeof layout)
(reduce + 0.0 (map sizeof layout)))))
(pass-if "alignof { int8, double, int8 }"
;; alignment of the most strictly aligned component
(let ((layout (list int8 double int8)))
(= (alignof layout) (alignof double))))
(pass-if "parse-c-struct"
(let ((layout (list int64 uint8))
(data (list -300 43)))
@ -266,6 +271,13 @@
(pass-if "int8, pointer, short, double"
(let ((layout (list int8 '* short double))
(data (list 77 %null-pointer -42 3.14)))
(equal? (parse-c-struct (make-c-struct layout data)
layout)
data)))
(pass-if "int8, { int8, double, int8 }, int16"
(let ((layout (list int8 (list int8 double int8) int16))
(data (list 77 (list 42 4.2 55) 88)))
(equal? (parse-c-struct (make-c-struct layout data)
layout)
data))))