Fix invalid use of __builtin_isnanf and __builtin_isnanl

[Bruno Haible]

Tim Rühsen wrote:
> - gcc-10 with unset CFLAGS (*.gcc-10)
> - clang-10 with unset CFLAGS (*.clang-10)

Another difference between these test results is this:

-gl_cv_func_isnanf_no_libm=${gl_cv_func_isnanf_no_libm=yes}
-gl_cv_func_isnanf_works=${gl_cv_func_isnanf_works=yes}
-gl_cv_func_isnanl_no_libm=${gl_cv_func_isnanl_no_libm=yes}
-gl_cv_func_isnanl_works=${gl_cv_func_isnanl_works=yes}
+gl_cv_func_isnanf_in_libm=${gl_cv_func_isnanf_in_libm=no}
+gl_cv_func_isnanf_no_libm=${gl_cv_func_isnanf_no_libm=no}
+gl_cv_func_isnanl_in_libm=${gl_cv_func_isnanl_in_libm=no}
+gl_cv_func_isnanl_no_libm=${gl_cv_func_isnanl_no_libm=no}

config.log shows that clang has no __builtin_isnanf and __builtin_isnanl,
although it defines __GNUC__ to a value >= 4. This patch fixes it.


2020-05-23  Bruno Haible  <address@hidden>

        isnanf, isnanl, isnan: Don't use nonexistent builtins with clang.
        * m4/isnanf.m4 (gl_HAVE_ISNANF_NO_LIBM, gl_HAVE_ISNANF_IN_LIBM,
        gl_ISNANF_WORKS): Don't use __builtin_isnanf on clang versions that
        don't have it.
        * m4/isnanl.m4 (gl_HAVE_ISNANL_NO_LIBM, gl_HAVE_ISNANL_IN_LIBM,
        gl_FUNC_ISNANL_WORKS): Don't use __builtin_isnanl on clang versions that
        don't have it.
        * lib/isnanf-nolibm.h (__has_builtin): New macro.
        (isnanf): Don't use __builtin_isnanf on clang versions that don't have
        it.
        * lib/isnanl-nolibm.h (__has_builtin): New macro.
        (isnanl): Don't use __builtin_isnanl on clang versions that don't have
        it.
        * lib/math.in.h (__has_builtin): New macro.
        (isnanf): Don't use __builtin_isnanf on clang versions that don't have
        it.
        (isnanl): Don't use __builtin_isnanl on clang versions that don't have
        it.
        (isnan): Don't use the builtins on clang versions that don't have
        __builtin_isnanf and __builtin_isnanl.

diff --git a/lib/isnanf-nolibm.h b/lib/isnanf-nolibm.h
index 647ffed..17a2f5e 100644
--- a/lib/isnanf-nolibm.h
+++ b/lib/isnanf-nolibm.h
@@ -17,7 +17,10 @@
 #if HAVE_ISNANF_IN_LIBC
 /* Get declaration of isnan macro or (older) isnanf function.  */
 # include <math.h>
-# if __GNUC__ >= 4
+# ifndef __has_builtin
+#  define __has_builtin(name) 0
+# endif
+# if __GNUC__ >= 4 && (!defined __clang__ || __has_builtin (__builtin_isnanf))
    /* GCC 4.0 and newer provides three built-ins for isnan.  */
 #  undef isnanf
 #  define isnanf(x) __builtin_isnanf ((float)(x))
diff --git a/lib/isnanl-nolibm.h b/lib/isnanl-nolibm.h
index c45e3ab..103d31a 100644
--- a/lib/isnanl-nolibm.h
+++ b/lib/isnanl-nolibm.h
@@ -17,7 +17,10 @@
 #if HAVE_ISNANL_IN_LIBC
 /* Get declaration of isnan macro or (older) isnanl function.  */
 # include <math.h>
-# if __GNUC__ >= 4
+# ifndef __has_builtin
+#  define __has_builtin(name) 0
+# endif
+# if __GNUC__ >= 4 && (!defined __clang__ || __has_builtin (__builtin_isnanl))
    /* GCC 4.0 and newer provides three built-ins for isnan.  */
 #  undef isnanl
 #  define isnanl(x) __builtin_isnanl ((long double)(x))
diff --git a/lib/math.in.h b/lib/math.in.h
index e5e37d6..30465f8 100644
--- a/lib/math.in.h
+++ b/lib/math.in.h
@@ -127,6 +127,12 @@ static void (*_gl_math_fix_itold) (long double *, int) = 
_Qp_itoq;
 #endif
 
 
+/* For clang: Use __has_builtin to determine whether a builtin is available.  
*/
+#ifndef __has_builtin
+# define __has_builtin(name) 0
+#endif
+
+
 /* POSIX allows platforms that don't support NAN.  But all major
    machines in the past 15 years have supported something close to
    IEEE NaN, so we define this unconditionally.  We also must define
@@ -2318,7 +2324,7 @@ _GL_WARN_REAL_FLOATING_DECL (isinf);
 # if @HAVE_ISNANF@
 /* The original <math.h> included above provides a declaration of isnan macro
    or (older) isnanf function.  */
-#  if __GNUC__ >= 4
+#  if __GNUC__ >= 4 && (!defined __clang__ || __has_builtin (__builtin_isnanf))
     /* GCC 4.0 and newer provides three built-ins for isnan.  */
 #   undef isnanf
 #   define isnanf(x) __builtin_isnanf ((float)(x))
@@ -2362,7 +2368,7 @@ _GL_EXTERN_C int isnand (double x);
 # if @HAVE_ISNANL@
 /* The original <math.h> included above provides a declaration of isnan
    macro or (older) isnanl function.  */
-#  if __GNUC__ >= 4
+#  if __GNUC__ >= 4 && (!defined __clang__ || __has_builtin (__builtin_isnanl))
     /* GCC 4.0 and newer provides three built-ins for isnan.  */
 #   undef isnanl
 #   define isnanl(x) __builtin_isnanl ((long double)(x))
@@ -2385,7 +2391,7 @@ _GL_EXTERN_C int isnanl (long double x) 
_GL_ATTRIBUTE_CONST;
    isnanf.h (e.g.) here, because those may end up being macros
    that recursively expand back to isnan.  So use the gnulib
    replacements for them directly. */
-#  if @HAVE_ISNANF@ && __GNUC__ >= 4
+#  if @HAVE_ISNANF@ && __GNUC__ >= 4 && (!defined __clang__ || __has_builtin 
(__builtin_isnanf))
 #   define gl_isnan_f(x) __builtin_isnanf ((float)(x))
 #  else
 _GL_EXTERN_C int rpl_isnanf (float x);
@@ -2397,7 +2403,7 @@ _GL_EXTERN_C int rpl_isnanf (float x);
 _GL_EXTERN_C int rpl_isnand (double x);
 #   define gl_isnan_d(x) rpl_isnand (x)
 #  endif
-#  if @HAVE_ISNANL@ && __GNUC__ >= 4
+#  if @HAVE_ISNANL@ && __GNUC__ >= 4 && (!defined __clang__ || __has_builtin 
(__builtin_isnanl))
 #   define gl_isnan_l(x) __builtin_isnanl ((long double)(x))
 #  else
 _GL_EXTERN_C int rpl_isnanl (long double x) _GL_ATTRIBUTE_CONST;
@@ -2408,7 +2414,7 @@ _GL_EXTERN_C int rpl_isnanl (long double x) 
_GL_ATTRIBUTE_CONST;
    (sizeof (x) == sizeof (long double) ? gl_isnan_l (x) : \
     sizeof (x) == sizeof (double) ? gl_isnan_d (x) : \
     gl_isnan_f (x))
-# elif __GNUC__ >= 4
+# elif __GNUC__ >= 4 && (!defined __clang__ || (__has_builtin 
(__builtin_isnanf) && __has_builtin (__builtin_isnanl)))
 #  undef isnan
 #  define isnan(x) \
    (sizeof (x) == sizeof (long double) ? __builtin_isnanl ((long double)(x)) : 
\
diff --git a/m4/isnanf.m4 b/m4/isnanf.m4
index 4e9fb48..7dd67bd 100644
--- a/m4/isnanf.m4
+++ b/m4/isnanf.m4
@@ -1,4 +1,4 @@
-# isnanf.m4 serial 15
+# isnanf.m4 serial 16
 dnl Copyright (C) 2007-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -74,7 +74,10 @@ AC_DEFUN([gl_HAVE_ISNANF_NO_LIBM],
       AC_LINK_IFELSE(
         [AC_LANG_PROGRAM(
            [[#include <math.h>
-             #if __GNUC__ >= 4
+             #ifndef __has_builtin
+             # define __has_builtin(name) 0
+             #endif
+             #if __GNUC__ >= 4 && (!defined __clang__ || __has_builtin 
(__builtin_isnanf))
              # undef isnanf
              # define isnanf(x) __builtin_isnanf ((float)(x))
              #elif defined isnan
@@ -99,7 +102,10 @@ AC_DEFUN([gl_HAVE_ISNANF_IN_LIBM],
       AC_LINK_IFELSE(
         [AC_LANG_PROGRAM(
            [[#include <math.h>
-             #if __GNUC__ >= 4
+             #ifndef __has_builtin
+             # define __has_builtin(name) 0
+             #endif
+             #if __GNUC__ >= 4 && (!defined __clang__ || __has_builtin 
(__builtin_isnanf))
              # undef isnanf
              # define isnanf(x) __builtin_isnanf ((float)(x))
              #elif defined isnan
@@ -127,7 +133,10 @@ AC_DEFUN([gl_ISNANF_WORKS],
       AC_RUN_IFELSE(
         [AC_LANG_SOURCE([[
 #include <math.h>
-#if __GNUC__ >= 4
+#ifndef __has_builtin
+# define __has_builtin(name) 0
+#endif
+#if __GNUC__ >= 4 && (!defined __clang__ || __has_builtin (__builtin_isnanf))
 # undef isnanf
 # define isnanf(x) __builtin_isnanf ((float)(x))
 #elif defined isnan
diff --git a/m4/isnanl.m4 b/m4/isnanl.m4
index 9874418..75d54629 100644
--- a/m4/isnanl.m4
+++ b/m4/isnanl.m4
@@ -1,4 +1,4 @@
-# isnanl.m4 serial 20
+# isnanl.m4 serial 21
 dnl Copyright (C) 2007-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -68,7 +68,10 @@ AC_DEFUN([gl_HAVE_ISNANL_NO_LIBM],
       AC_LINK_IFELSE(
         [AC_LANG_PROGRAM(
            [[#include <math.h>
-             #if __GNUC__ >= 4
+             #ifndef __has_builtin
+             # define __has_builtin(name) 0
+             #endif
+             #if __GNUC__ >= 4 && (!defined __clang__ || __has_builtin 
(__builtin_isnanl))
              # undef isnanl
              # define isnanl(x) __builtin_isnanl ((long double)(x))
              #elif defined isnan
@@ -93,7 +96,10 @@ AC_DEFUN([gl_HAVE_ISNANL_IN_LIBM],
       AC_LINK_IFELSE(
         [AC_LANG_PROGRAM(
            [[#include <math.h>
-             #if __GNUC__ >= 4
+             #ifndef __has_builtin
+             # define __has_builtin(name) 0
+             #endif
+             #if __GNUC__ >= 4 && (!defined __clang__ || __has_builtin 
(__builtin_isnanl))
              # undef isnanl
              # define isnanl(x) __builtin_isnanl ((long double)(x))
              #elif defined isnan
@@ -123,7 +129,10 @@ AC_DEFUN([gl_FUNC_ISNANL_WORKS],
 #include <float.h>
 #include <limits.h>
 #include <math.h>
-#if __GNUC__ >= 4
+#ifndef __has_builtin
+# define __has_builtin(name) 0
+#endif
+#if __GNUC__ >= 4 && (!defined __clang__ || __has_builtin (__builtin_isnanl))
 # undef isnanl
 # define isnanl(x) __builtin_isnanl ((long double)(x))
 #elif defined isnan