I get the following warnings, when building on Mac OS X.
(It should show up for all platforms, though):
In file included from
/Users/jens/open-source/Source/guile-2.0.12/libguile/numbers.c:9731:
/Users/jens/open-source/Source/guile-2.0.12/libguile/conv-integer.i.c: In
function 'scm_to_int8':
/Users/jens/open-source/Source/guile-2.0.12/libguile/conv-integer.i.c:94:
warning: comparison is always true due to limited range of data type
/Users/jens/open-source/Source/guile-2.0.12/libguile/conv-integer.i.c:94:
warning: comparison is always true due to limited range of data type
In file included from
/Users/jens/open-source/Source/guile-2.0.12/libguile/numbers.c:9747:
/Users/jens/open-source/Source/guile-2.0.12/libguile/conv-integer.i.c: In
function 'scm_to_int16':
/Users/jens/open-source/Source/guile-2.0.12/libguile/conv-integer.i.c:94:
warning: comparison is always true due to limited range of data type
/Users/jens/open-source/Source/guile-2.0.12/libguile/conv-integer.i.c:94:
warning: comparison is always true due to limited range of data type
Notice that it's only from line 94, which reads...
if (n >= TYPE_MIN && n <= TYPE_MAX)
... looking at the top of the file, it says: "It is only for signed types", so
I look in ...
numbers.c:9731
numbers.c:9747
... which is int8 and int16 (signed integers); this should be as intended.
The variable 'n' is declared as scm_t_signed_bits, which is a scm_t_intptr,
which is an intptr_t, which is just a 'long'.
So my guess is that the problem must be with TYPE_MIN and TYPE_MAX.
In numbers.c, line 9742, they're defined as follows:
#define TYPE scm_t_int16
#define TYPE_MIN SCM_T_INT16_MIN
#define TYPE_MAX SCM_T_INT16_MAX
... looks good to me, but where's the definition of SCM_T_INT16_MIN and
SCM_T_INT16_MAX ?
-It seems to be in __scm.h:
#define SCM_I_UTYPE_MAX(type) ((type)-1)
#define SCM_I_TYPE_MAX(type,umax) ((type)((umax)/2))
#define SCM_I_TYPE_MIN(type,umax) (-((type)((umax)/2))-1)
#define SCM_T_UINT8_MAX SCM_I_UTYPE_MAX(scm_t_uint8)
#define SCM_T_INT8_MIN SCM_I_TYPE_MIN(scm_t_int8,SCM_T_UINT8_MAX)
#define SCM_T_INT8_MAX SCM_I_TYPE_MAX(scm_t_int8,SCM_T_UINT8_MAX)
#define SCM_T_UINT16_MAX SCM_I_UTYPE_MAX(scm_t_uint16)
#define SCM_T_INT16_MIN SCM_I_TYPE_MIN(scm_t_int16,SCM_T_UINT16_MAX)
#define SCM_T_INT16_MAX SCM_I_TYPE_MAX(scm_t_int16,SCM_T_UINT16_MAX)
Now, this is where things get interesting. The macros are cool, but I think the
use seems to be incorrect.
Let's try an example (SCM_T_INT16_MIN):
SCM_T_INT16_MIN = SCM_I_TYPE_MIN(scm_t_int16,SCM_T_UINT16_MAX)
Expands to ...
SCM_T_INT16_MIN = (-((scm_t_int16)((-1)/2))-1)
... which can be cleaned up ...
SCM_T_INT16_MIN = (-(((-1)/2))-1)
A signed integer of value -1 divided by 2, is the same as bitshifting to the
right by using ASR; the result will be -1.
SCM_T_INT16_MIN = (-(((-1)))-1)
SCM_T_INT16_MIN = (-((-1))-1)
SCM_T_INT16_MIN = (-(-1)-1)
SCM_T_INT16_MIN = (+1-1)
SCM_T_INT16_MIN = (0)
... Ehm ... Did I do something wrong ?
I expected the value -32768, but got 0.
Wouldn't it be correct to typecast as scm_t_uint16 instead of scm_t_int16 (and
thus scm_t_uint8 instead of scm_t_int8) ?
Love
Jens
