Add isinf module.

[gnulib.git] / m4 / isinf.m4

diff --git a/m4/isinf.m4 b/m4/isinf.m4
new file mode 100644 (file)
index 0000000..1b9e45a
--- /dev/null
+++ b/m4/isinf.m4
@@ -0,0 +1,49 @@
+# isinf.m4 serial 1
+dnl Copyright (C) 2007-2008 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_ISINF],
+[
+  AC_REQUIRE([gl_MATH_H_DEFAULTS])
+  dnl Persuade glibc <math.h> to declare isinf.
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+  AC_CHECK_DECLS([isinf], , , [#include <math.h>])
+  if test "$ac_cv_have_decl_isinf" = yes; then
+    gl_CHECK_MATH_LIB([ISINF_LIBM], [x = isinf (x);])
+    if test "$ISINF_LIBM" != missing; then
+      dnl Test whether isinf() on 'long double' works.
+      gl_ISINFL_WORKS
+      case "$gl_cv_func_isinfl_works" in
+        *yes) ;;
+        *)    ISINF_LIBM=missing;;
+      esac
+    fi
+  fi
+  if test "$ac_cv_have_decl_isinf" != yes ||
+     test "$ISINF_LIBM" = missing; then
+    REPLACE_ISINF=1
+    AC_LIBOBJ([isinf])
+    ISINF_LIBM=
+  fi
+  AC_SUBST([REPLACE_ISINF])
+  AC_SUBST([ISINF_LIBM])
+])
+
+dnl Test whether isinf() correctly returns false for LDBL_MAX.
+AC_DEFUN([gl_ISINFL_WORKS],
+[
+  AC_REQUIRE([AC_PROG_CC])
+  AC_REQUIRE([AC_C_BIGENDIAN])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  AC_CACHE_CHECK([whether isinf(long double) works], [gl_cv_func_isinfl_works],
+    [
+      AC_RUN_IFELSE([AC_LANG_PROGRAM([[#include <float.h>
+                                       #include <math.h>]],
+                                     [[return !!isinf(LDBL_MAX);]])],
+                    [gl_cv_func_isinfl_works=yes],
+                    [gl_cv_func_isinfl_works=no],
+                   [gl_cv_func_isinfl_works="guessing no"])
+    ])
+])