> On Jul 13, 2018, at 9:36 AM, Janus Weil <ja...@gcc.gnu.org> wrote:
>
> Hi Paul,
>
> Fortran problems are best discussed on fort...@gcc.gnu.org
> <mailto:fort...@gcc.gnu.org> (in CC) ...
>
> 2018-07-12 21:22 GMT+02:00 Paul Koning <paulkon...@comcast.net
> <mailto:paulkon...@comcast.net>>:
>> I tried to rebuild for target pdp11 with fortran enabled (in the past I've
>> just enabled C). It builds fine but the resulting compiler crashes at
>> startup:
>>
>> Paul-Konings-MacBook-Pro:gcc pkoning$ ./xgcc -B. -O2 -S ../../hello.f
>> f951: internal compiler error: gfc_validate_kind(): Got bad kind
>> libbacktrace could not find executable to open
>> Please submit a full bug report,
>> with preprocessed source if appropriate.
>> See <https://gcc.gnu.org/bugs/> for instructions.
>>
>> "hello.f" is the typical "hello world" program. Some debugging got me to
>> here:
>>
>> * thread #1, queue = 'com.apple.main-thread', stop reason = step over
>> frame #0: 0x00000001001c1c93 f951`gfc_init_kinds() [inlined]
>> gfc_validate_kind(type=BT_REAL, kind=<unavailable>, may_fail=false) at
>> trans-types.c:814 [opt]
>> 811 }
>> 812
>> 813 if (rc < 0 && !may_fail)
>> -> 814 gfc_internal_error ("gfc_validate_kind(): Got bad kind");
>> 815
>> 816 return rc;
>> 817 }
>> Target 0: (f951) stopped.
>>
>> So it's unhappy about some "kind", for BT_REAL. I'm not sure what that
>> means. Is it mapping the available data types to Fortran "KIND" values? If
>> so, is there something the target has to do for this to work? Note that
>> this isn't an IEEE target, so if the initialization is expecting IEEE float
>> then that may account for it. But I have no idea what to do here, and the
>> manual offers no clue.
>
> A "kind" in Fortran is the size of the data type in bytes. E.g.
> "real(kind=4)" would be a 'single-precision' 32-bit float number,
> while "real(kind=8)" would be a 'double-precision' 64-bit float
> number. The default kind for REAL variables is 4 in gfortran, see:
>
> https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gfortran/KIND-Type-Parameters.html
> <https://gcc.gnu.org/onlinedocs/gcc-8.1.0/gfortran/KIND-Type-Parameters.html>
>
> Since pdp-11 seems to be a 16-bit platform, such a 32-bit
> floating-point type might not be available there? Possibly it makes
> sense to set the default REAL kind to 2 for such a target?
No, because there isn't a 16 bit float type on that machine. But your answer
pointed me straight to the problem.
The pdp11 back end has a command line option to choose whether the C "float"
type is SFmode or DFmode (32 bit or 64 bit). For various reasons, it defaults
to 64, which of course means that "float" and "double" are the same machine
type -- the only float is "real(kind=8)". If I override the default with
-mfloat32, Fortran is happy. Maybe the right answer is to change the default,
at least once I take away the historic reason for it.
Thanks!
paul
