isnanf, isnand, isnanl: Fix link errors on AIX 7.1 with xlc

[Bruno Haible]

In a testdir for modules totalorder, totalorderf, totalorderl on AIX 7.1
with xlc, I see these link errors:

xlc -q64 -qthreaded -qtls  -g  -L/home/haible/prefix64/lib -o 
test-isnand-nolibm test-isnand-nolibm.o libtests.a ../gllib/libgnu.a libtests.a 
../gllib/libgnu.a libtests.a  
ld: 0711-317 ERROR: Undefined symbol: ._isnan
ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more information.
gmake[4]: *** [Makefile:1821: test-isnand-nolibm] Error 8
xlc -q64 -qthreaded -qtls  -g  -L/home/haible/prefix64/lib -o 
test-isnanf-nolibm test-isnanf-nolibm.o libtests.a ../gllib/libgnu.a libtests.a 
../gllib/libgnu.a libtests.a  
ld: 0711-317 ERROR: Undefined symbol: ._isnanf
ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more information.
gmake[4]: *** [Makefile:1829: test-isnanf-nolibm] Error 8
xlc -q64 -qthreaded -qtls  -g  -L/home/haible/prefix64/lib -o 
test-isnanl-nolibm test-isnanl-nolibm.o libtests.a ../gllib/libgnu.a libtests.a 
../gllib/libgnu.a libtests.a  
ld: 0711-317 ERROR: Undefined symbol: ._isnan
ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more information.
gmake[4]: *** [Makefile:1837: test-isnanl-nolibm] Error 8

The cause it that <math.h> undoes the macro definitions done by
isnan?-nolibm.h.

This patch fixes it.


2024-06-02  Bruno Haible  <bruno@clisp.org>

        isnanf, isnand, isnanl: Fix link errors on AIX 7.1 with xlc.
        * lib/isnanf-nolibm.h (HAVE_ISNANF_NOLIBM): New macro.
        * lib/isnand-nolibm.h (HAVE_ISNAND_NOLIBM): New macro.
        * lib/isnanl-nolibm.h (HAVE_ISNANL_NOLIBM): New macro.
        * lib/math.h (isnanf): Don't define via isnan if HAVE_ISNANF_NOLIBM is
        defined.
        (isnand): Don't define via isnan if HAVE_ISNAND_NOLIBM is defined.
        (isnanl): Don't define via isnan if HAVE_ISNANL_NOLIBM is defined.

diff --git a/lib/isnand-nolibm.h b/lib/isnand-nolibm.h
index 925e71d17a..1a0f27b412 100644
--- a/lib/isnand-nolibm.h
+++ b/lib/isnand-nolibm.h
@@ -40,3 +40,6 @@ extern
 # endif
 int isnand (double x);
 #endif
+
+/* Tell <math.h> that our isnand does not need libm.  */
+#define HAVE_ISNAND_NOLIBM 1
diff --git a/lib/isnanf-nolibm.h b/lib/isnanf-nolibm.h
index 06f0cbb70d..d004bbe8fe 100644
--- a/lib/isnanf-nolibm.h
+++ b/lib/isnanf-nolibm.h
@@ -52,3 +52,6 @@ extern
 # endif
 int isnanf (float x);
 #endif
+
+/* Tell <math.h> that our isnanf does not need libm.  */
+#define HAVE_ISNANF_NOLIBM 1
diff --git a/lib/isnanl-nolibm.h b/lib/isnanl-nolibm.h
index 0b6755cd82..f0219dea88 100644
--- a/lib/isnanl-nolibm.h
+++ b/lib/isnanl-nolibm.h
@@ -41,3 +41,6 @@ extern
 # endif
 int isnanl (long double x);
 #endif
+
+/* Tell <math.h> that our isnanl does not need libm.  */
+#define HAVE_ISNANL_NOLIBM 1
diff --git a/lib/math.in.h b/lib/math.in.h
index 96d0da44fd..a1ae4e7328 100644
--- a/lib/math.in.h
+++ b/lib/math.in.h
@@ -2557,7 +2557,7 @@ _GL_EXTERN_C int isnanf (float x);
        GCC >= 4.0 also provides __builtin_isnanf, but clang doesn't.  */
 #    undef isnanf
 #    define isnanf(x) __builtin_isnan ((float)(x))
-#   elif defined isnan
+#   elif defined isnan && !defined HAVE_ISNANF_NOLIBM
 #    undef isnanf
 #    define isnanf(x) isnan ((float)(x))
 #   endif
@@ -2586,7 +2586,7 @@ _GL_EXTERN_C int isnand (double x);
     /* GCC >= 4.0 and clang provide a type-generic built-in for isnan.  */
 #    undef isnand
 #    define isnand(x) __builtin_isnan ((double)(x))
-#   else
+#   elif !defined HAVE_ISNAND_NOLIBM
 #    undef isnand
 #    define isnand(x) isnan ((double)(x))
 #   endif
@@ -2609,7 +2609,7 @@ _GL_EXTERN_C int isnand (double x);
        GCC >= 4.0 also provides __builtin_isnanl, but clang doesn't.  */
 #   undef isnanl
 #   define isnanl(x) __builtin_isnan ((long double)(x))
-#  elif defined isnan
+#  elif defined isnan && !defined HAVE_ISNANL_NOLIBM
 #   undef isnanl
 #   define isnanl(x) isnan ((long double)(x))
 #  endif