[gtk+] GTK: Fix build for pre-C99 compilers

[Chun-wei Fan <fanchunwei src gnome org>]

commit 092cb9e202a9f654152bc5fbb276521817346d11
Author: Chun-wei Fan <fanchunwei src gnome org>
Date:   Mon May 9 16:37:39 2016 +0800

    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      |   10 ++++++++++
 configure.ac           |    2 +-
 gtk/fallback-c89.c     |   27 +++++++++++++++++++++++++++
 gtk/gtkprogressbar.c   |    3 ++-
 gtk/inspector/visual.c |    2 +-
 5 files changed, 41 insertions(+), 3 deletions(-)
---
diff --git a/config.h.win32.in b/config.h.win32.in
index 8269db7..a73067e 100644
--- a/config.h.win32.in
+++ b/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 */
 
diff --git a/configure.ac b/configure.ac
index 3718dbf..2d4df24 100644
--- a/configure.ac
+++ b/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
diff --git a/gtk/fallback-c89.c b/gtk/fallback-c89.c
index e87bf76..df28048 100644
--- a/gtk/fallback-c89.c
+++ b/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
diff --git a/gtk/gtkprogressbar.c b/gtk/gtkprogressbar.c
index 9ba2c86..86c57a5 100644
--- a/gtk/gtkprogressbar.c
+++ b/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
diff --git a/gtk/inspector/visual.c b/gtk/inspector/visual.c
index f56f66e..b3da229 100644
--- a/gtk/inspector/visual.c
+++ b/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"