GTK: Fix build for pre-C99 compilers

Some compilers we support, such as pre-2013 Visual Studio, does not support
for INIFINITY, log2() and exp2(), so check for exp2() and log2() during
configure, and use fallbacks for them and INIFINTY if they are not found.

https://bugzilla.gnome.org/show_bug.cgi?id=766207

config.h.win32.in

@@ -50,6 +50,11 @@
 /* Define to 1 if you have the <dlfcn.h> header file. */
 /* #undef HAVE_DLFCN_H */
 
+/* Define to 1 if you have the `exp2' function. */
+#if !defined (_MSC_VER) || (_MSC_VER >= 1800)
+#define HAVE_EXP2 1
+#endif
+
 /* Define to 1 if you have the `flockfile' function. */
 #undef HAVE_FLOCKFILE
 
@@ -105,6 +110,11 @@
 /* Define to 1 if you have the `localtime_r' function. */
 /* #undef HAVE_LOCALTIME_R */
 
+/* Define to 1 if you have the `log2' function. */
+#if !defined (_MSC_VER) || (_MSC_VER >= 1800)
+#define HAVE_LOG2 1
+#endif
+
 /* Define to 1 if you have the `lstat' function. */
 /* #undef HAVE_LSTAT */
 

configure.ac

@@ -897,7 +897,7 @@ AC_TYPE_UID_T
 
 # Check for round(), rint(), isnan(), isinf() and nearbyint()
 AC_CHECK_LIB(m,round,,)
-AC_CHECK_FUNCS(round rint nearbyint sincos)
+AC_CHECK_FUNCS(round rint nearbyint sincos exp2 log2)
 AC_CHECK_DECLS([isnan, isinf], [], [], [[#include <math.h>]])
 
 # Checks for gdkspawn

gtk/fallback-c89.c

@@ -77,3 +77,30 @@ isinf (double x)
   return (!_finite (x) && !_isnan (x));
 }
 #endif
+
+#ifndef INFINITY
+/* define INFINITY for compilers that lack support for it */
+# ifdef HUGE_VALF
+#  define INFINITY HUGE_VALF
+# else
+#  define INFINITY (float)HUGE_VAL
+# endif
+#endif
+
+#ifndef HAVE_LOG2
+/* Use a simple implementation for log2() for compilers that lack it */
+static inline double
+log2 (double x)
+{
+  return log (x) / log (2.0);
+}
+#endif
+
+#ifndef HAVE_EXP2
+/* Use a simple implementation for exp2() for compilers that lack it */
+static inline double
+exp2 (double x)
+{
+  return pow (2.0, x);
+}
+#endif

gtk/gtkprogressbar.c

@@ -25,7 +25,6 @@
 #include "config.h"
 
 #include <string.h>
-#include <math.h>
 
 #include "gtkprogressbar.h"
 #include "gtkorientableprivate.h"
@@ -42,6 +41,8 @@
 
 #include "a11y/gtkprogressbaraccessible.h"
 
+#include "fallback-c89.c"
+
 /**
  * SECTION:gtkprogressbar
  * @Short_description: A widget which indicates progress visually

gtk/inspector/visual.c

@@ -31,7 +31,7 @@
 #include "gtkwindow.h"
 #include "gtkcssproviderprivate.h"
 
-#include <math.h>
+#include "fallback-c89.c"
 
 #ifdef GDK_WINDOWING_X11
 #include "x11/gdkx.h"