commit fa632b0019ad32dc1e45143d1f95cb91e32a00fc
Author: Peter TB Brett <peter.brett@livecode.com>
Date:   Wed Sep 21 05:37:44 2016 +0100

    build: Ensure config.h does not undefine `sqrtf`
    
    On Windows, `sqrtf` is a macro.  Previously, `configure` was detecting
    `sqrtf`'s availability, but then undefining it in `config.h`,
    resulting in link failures.
    
    This patch modifies `configure` to use `HAVE_SQRTF` as a feature macro
    for the `sqrtf()` function, and adds an additional stanza to
    `config.h` which defines a suitable alternative when `HAVE_SQRTF` is
    not defined.
    
    Signed-off-by: Peter TB Brett <peter.brett@livecode.com>

diff --git a/configure.ac b/configure.ac
index e833e45..b70e32d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -932,9 +932,16 @@ fi
 dnl =====================================
 dnl Check for missing sqrtf() as, e.g., for Solaris 9
 
-AC_SEARCH_LIBS([sqrtf], [m], [],
-               [AC_DEFINE([sqrtf], [sqrt],
-                          [Define to sqrt if you do not have the `sqrtf' function.])])
+AC_SEARCH_LIBS([sqrtf], [m],
+               [AC_DEFINE([HAVE_SQRTF], [1],
+                          [Whether we have sqrtf()])],
+               [])
+
+AH_VERBATIM([HAVE_SQRTF_MISSING],
+            [/* If sqrtf() is missing, use sqrt(). */
+#ifndef HAVE_SQRTF
+#define sqrtf sqrt
+#endif /* HAVE_SQRTF */])
 
 dnl =====================================
 dnl Thread local storage