remainderf: Override buggy system function on IRIX 6.5.

[gnulib.git] / m4 / logb.m4

diff --git a/m4/logb.m4 b/m4/logb.m4
index c5b6803..ee23e24 100644 (file)
--- a/m4/logb.m4
+++ b/m4/logb.m4
@@ -1,5 +1,5 @@
-# logb.m4 serial 1
-dnl Copyright (C) 2010 Free Software Foundation, Inc.
+# logb.m4 serial 5
+dnl Copyright (C) 2010-2012 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.
@@ -7,33 +7,47 @@ dnl with or without modifications, as long as this notice is preserved.
 AC_DEFUN([gl_FUNC_LOGB],
 [
   AC_REQUIRE([gl_MATH_H_DEFAULTS])
+
+  dnl Persuade glibc <math.h> to declare logb().
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+
   dnl Test whether logb() is declared.
-  AC_CHECK_DECLS([logb], , , [#include <math.h>])
+  AC_CHECK_DECLS([logb], , , [[#include <math.h>]])
   if test "$ac_cv_have_decl_logb" != yes; then
     HAVE_DECL_LOGB=0
   fi
   dnl Test whether logb() can be used without libm.
   LOGB_LIBM=?
-  AC_TRY_LINK([
-     #ifndef __NO_MATH_INLINES
-     # define __NO_MATH_INLINES 1 /* for glibc */
-     #endif
-     #include <math.h>
-     extern double logb (double x);
-     double x;],
-    [x = logb(x);],
+  AC_LINK_IFELSE(
+    [AC_LANG_PROGRAM(
+       [[#ifndef __NO_MATH_INLINES
+         # define __NO_MATH_INLINES 1 /* for glibc */
+         #endif
+         #include <math.h>
+         extern
+         #ifdef __cplusplus
+         "C"
+         #endif
+         double logb (double x);
+         double x;]],
+       [[x = logb(x);]])],
     [LOGB_LIBM=])
   if test "$LOGB_LIBM" = "?"; then
     save_LIBS="$LIBS"
     LIBS="$LIBS -lm"
-    AC_TRY_LINK([
-       #ifndef __NO_MATH_INLINES
-       # define __NO_MATH_INLINES 1 /* for glibc */
-       #endif
-       #include <math.h>
-       extern double logb (double x);
-       double x;],
-      [x = logb(x);],
+    AC_LINK_IFELSE(
+      [AC_LANG_PROGRAM(
+         [[#ifndef __NO_MATH_INLINES
+           # define __NO_MATH_INLINES 1 /* for glibc */
+           #endif
+           #include <math.h>
+           extern
+           #ifdef __cplusplus
+           "C"
+           #endif
+           double logb (double x);
+           double x;]],
+         [[x = logb(x);]])],
       [LOGB_LIBM="-lm"])
     LIBS="$save_LIBS"
   fi