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 37599212cef04b18a2c783f526b302e6f0e314b4..3bb3ba8100f1260003f6a13420b71078c3c4580b 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -435,6 +435,7 @@ 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_SUBST([MATH_LIBS])