math.h has a macro _Mlong_double_ for the type to use when declaring
long double functions, and similar macros for other types.
math/Makefile uses -D_Mlong_double_=double in the case of long double
having the same ABI as double.
This originates with:
Mon Jul 8 13:37:40 1996 Roland McGrath <roland@delasyd.gnu.ai.mit.edu>
* math/math.h (_Mfloat_, _Mlong_double_): New macros, defined iff not
already defined to float, long double. Use those macros for _Mdouble_
defns when including mathcalls.h.
* math/Makefile [$(long-double-fcts) != yes] (CPPFLAGS): Append
-D_Mlong_double_=double.
However, math.h stopped declaring long double functions in the case of
long double having the same ABI as double (and thus probably stopped
actually needing the Makefile definition of _Mlong_double_) with:
1998-11-05 Ulrich Drepper <drepper@cygnus.com>
* math/math.h: Unconditionally include bits/mathdef.h. Declare
long double functions only if __NO_LONG_DOUBLE_MATH is not
defined.
* sysdeps/generic/bits/mathdef.h: Define only if __USE_ISOC9X.
Define __NO_LONG_DOUBLE_MATH.
* sysdeps/m68k/fpu/bits/mathdef.h: Define only if __USE_ISOC9X.
* sysdeps/i386/fpu/bits/mathdef.h: Likewise.
The declarations were since restored for compiling user code, but
remain absent when _LIBC is defined, which is sufficient to avoid
problems declaring function aliases of incompatible types. Thus the
indirection through the _Mlong_double_ macro is not needed (probably
since that 1998 patch), and this patch removes _Mlong_double_ and
associated macros for other types, leaving only the macro _Mdouble_
which is actually used as the type for which a given inclusion of
<bits/mathcalls.h> should declared functions.
Tested for x86_64, and tested with build-many-glibcs.py that installed
stripped shared libraries are unchanged by this patch.
* math/math.h [!_Mfloat_] (_Mfloat_): Do not define.
[!_Mlong_double_] (_Mlong_double_): Likewise.
[!_Mfloat16_] (_Mfloat16_): Likewise.
[!_Mfloat32_] (_Mfloat32_): Likewise.
[!_Mfloat64_] (_Mfloat64_): Likewise.
[!_Mfloat128_] (_Mfloat128_): Likewise.
[!_Mfloat32x_] (_Mfloat32x_): Likewise.
[!_Mfloat64x_] (_Mfloat64x_): Likewise.
[!_Mfloat128x_] (_Mfloat128x_): Likewise.
(_Mdouble_): Define without indirection through those macros.
* math/complex.h [!_Mfloat_] (_Mfloat_): Do not define.
[!_Mfloat128_] (_Mfloat128_): Likewise.
[_Mlong_double_] (_Mlong_double_): Likewise.
(_Mdouble_): Define without indirection through those macros.
* math/Makefile [$(long-double-fcts) != yes] (math-CPPFLAGS): Do
not add -D_Mlong_double_=double.
* include/math.h [_ISOMAC] (_Mlong_double_): Do not undefine.
* math/test-signgam-finite-c99.c (_Mlong_double_): Likewise.
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