build-sys: improve detection of the "isnan" function in uClibc

Since commit beceb14b450ded6560ed743634a5e80604a8edf3, MATH_LIBS is set
to "-lm" when the isnan function is detected. In uClibc, however, isnan
is a macro that calls __isnan, __isnanf, or __isnanl, depending on the
size of the argument (double, float or long double).

Fixes:
  http://autobuild.buildroot.net/results/2c2/2c29a78ed81ca844a87dcd076ab3e14ea080296d/
  http://autobuild.buildroot.net/results/404/404b10f359b2ae8a7216729fa1bab37fed2d3d4c/

Signed-off-by: Carlos Santos <casantos@datacom.ind.br>

diff --git a/configure.ac b/configure.ac
index cc0563b9a0705dd0f9ea1c952b1cc28812271661..d03469c9c624f71c6bc6c29b7bc9f3949812887e 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -428,7 +428,8 @@ AC_CHECK_FUNCS([reboot], [have_reboot=yes],[have_reboot=no])
 AM_CONDITIONAL([HAVE_OPENAT], [test "x$have_openat" = xyes])
 
 AC_CHECK_FUNCS([isnan], [],
-       [AC_CHECK_LIB([m], [isnan], [MATH_LIBS="-lm"])]
+       [AC_CHECK_LIB([m], [isnan], [MATH_LIBS="-lm"])]
+       [AC_CHECK_LIB([m], [__isnan], [MATH_LIBS="-lm"])]
 )
 AC_SUBST([MATH_LIBS])