fix compilation errors on HP-UX 11/ia64

[Bruno Haible]

On HP-UX 11.31/ia64 I'm seeing these errors:

DEPDIR=.deps depmode=hp2 /bin/sh ../../build-aux/depcomp \
cc +DD64 -AC99 -D_XOPEN_SOURCE=500 -DHAVE_CONFIG_H -I. -I../../gllib -I..  
-DGNULIB_STRICT_CHECKING=1 -I/home/haible/prefix-hpux113ia64-64-cc/include  -g 
-c -o math.o ../../gllib/math.c
"./math.h", line 977: error #2040: expected an identifier
  _GL_FUNCDECL_SYS (copysignf, float, (float x, float y));
  ^

"./math.h", line 977: error #2018: expected a ")"
  _GL_FUNCDECL_SYS (copysignf, float, (float x, float y));
  ^

"./math.h", line 1388: error #2040: expected an identifier
  _GL_FUNCDECL_SYS (fmaf, float, (float x, float y, float z));
  ^

"./math.h", line 1388: error #2018: expected a ")"
  _GL_FUNCDECL_SYS (fmaf, float, (float x, float y, float z));
  ^

"./math.h", line 1411: error #2040: expected an identifier
  _GL_FUNCDECL_SYS (fma, double, (double x, double y, double z));
  ^

"./math.h", line 1411: error #2018: expected a ")"
  _GL_FUNCDECL_SYS (fma, double, (double x, double y, double z));
  ^

6 errors detected in the compilation of "../../gllib/math.c".
gmake[4]: *** [math.o] Error 2


This patch fixes it.


2019-12-08  Bruno Haible  <br...@clisp.org>

        Fix compilation errors on HP-UX 11/ia64.
        * lib/math.in.h (copysignf, fmaf, fma): Undefine before
        _GL_FUNCDECL_SYS.

diff --git a/lib/math.in.h b/lib/math.in.h
index 55130ab..18f8ff3 100644
--- a/lib/math.in.h
+++ b/lib/math.in.h
@@ -500,6 +500,7 @@ _GL_WARN_ON_USE (ceill, "ceill is unportable - "
 
 #if @GNULIB_COPYSIGNF@
 # if !@HAVE_DECL_COPYSIGNF@
+#  undef copysignf
 _GL_FUNCDECL_SYS (copysignf, float, (float x, float y));
 # endif
 _GL_CXXALIAS_SYS (copysignf, float, (float x, float y));
@@ -911,6 +912,7 @@ _GL_FUNCDECL_RPL (fmaf, float, (float x, float y, float z));
 _GL_CXXALIAS_RPL (fmaf, float, (float x, float y, float z));
 # else
 #  if !@HAVE_FMAF@
+#   undef fmaf
 _GL_FUNCDECL_SYS (fmaf, float, (float x, float y, float z));
 #  endif
 _GL_CXXALIAS_SYS (fmaf, float, (float x, float y, float z));
@@ -934,6 +936,7 @@ _GL_FUNCDECL_RPL (fma, double, (double x, double y, double 
z));
 _GL_CXXALIAS_RPL (fma, double, (double x, double y, double z));
 # else
 #  if !@HAVE_FMA@
+#   undef fma
 _GL_FUNCDECL_SYS (fma, double, (double x, double y, double z));
 #  endif
 _GL_CXXALIAS_SYS (fma, double, (double x, double y, double z));