https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101104
--- Comment #14 from Segher Boessenkool <segher at gcc dot gnu.org> ---
(In reply to Patrick McGehearty from comment #13)
> I may be mistaken about the source of the issue being glibc.
> Perhaps it is a system include file issue? Here are some
> more details.
>
> Here are some of the error messages I got when building with
> __LIBGCC_KF_MAX__ of gcc135.fsffrance.org using the installed
> gcc (gcc version 4.8.5 20150623 (Red Hat 4.8.5-44) (GCC))
>
> - - - - - -
> ../../../libgcc/config/rs6000/_divkc3.c: In function ‘__divkc3’:
> ../../../libgcc/config/rs6000/_divkc3.c:41:17: error:
> ‘__LIBGCC_KF_MAX__’ undeclared (first use in this function)
> 41 | #define RBIG (__LIBGCC_KF_MAX__ / 2)
> | ^~~~~~~~~~~~~~~~~
> ../../../libgcc/config/rs6000/_divkc3.c:68:23: note: in expansion of
> macro ‘RBIG’
> 68 | if (FABS (d) >= RBIG)
> | ^~~~
> ... repeated for ‘__LIBGCC_KF_EPSILON__ and __LIBGCC_KF_MIN__
> - - - - - -
This is defined be GCC itself. But not in the configuration you built.
This requires VSX (currently).
The problem is in the _divkc3.c code.
> __LIBGCC_KF_MAX__ should have been defined in the file
> gcc/c-family/c-cppbuiltin.c
> in the loop starting at line 1274:
> /* Properties of floating-point modes for libgcc2.c. */
> opt_scalar_float_mode mode_iter;
> FOR_EACH_MODE_IN_CLASS (mode_iter, MODE_FLOAT)
> {
> scalar_float_mode mode = mode_iter.require ();
The mode does not exist in this config. The macro should not have been
defined.
> KF is not available with this particular compiler/glibc
> combination.
KF is not available if you use -mno-vsx. This is the default in most
configurations.
> I did some digging in the latest sources and could not find a specific file
> which defined KF, TF, IF, etc. I assume it exists and I just did not
> look in the
> right places.
rs6000-modes.def . You need TARGET_FLOAT128_TYPE set to be able to use it;
you normally get
TARGET_FLOAT128_TYPE = TARGET_FLOAT128_ENABLE_TYPE && TARGET_VSX;
> In any case, it is moot since Joseph Myers stated that I should not
> include the
> "if compiling for ibm doubledouble" code in _divkc3.c because _divkc3.c
> is only
> used for ieee128 code. Since he is the one who guided me in my changes
> to c-cppbuiltin.c,
> I assume he knows more than I on this topic.
Ah :-) That is essential context. I did not know you hadn't done this yet.
