Use atexit() only if it's safe to call from shared library
Apparently they are not (advertised as?) safe on BSD systems.
We ignore the case of static libraries.
Whitelisted on glibc, Android, and MSVC / mingw.
https://bugs.freedesktop.org/show_bug.cgi?id=82246
diff --git a/src/hb-private.hh b/src/hb-private.hh
index 5a4ca69..1b39e57 100644
--- a/src/hb-private.hh
+++ b/src/hb-private.hh
@@ -130,6 +130,31 @@
# define STRICT
#endif
+#if HAVE_ATEXIT
+/* atexit() is only safe to be called from shared libraries on certain
+ * platforms. Whitelist.
+ * https://bugs.freedesktop.org/show_bug.cgi?id=82246 */
+# if defined(__linux) && defined(__GLIBC_PREREQ)
+# if __GLIBC_PREREQ(2,3)
+/* From atexit() manpage, it's safe with glibc 2.2.3 on Linux. */
+# define HB_USE_ATEXIT 1
+# endif
+# elif defined(_MSC_VER) || defined(__MINGW32__)
+/* For MSVC:
+ * http://msdn.microsoft.com/en-ca/library/tze57ck3.aspx
+ * http://msdn.microsoft.com/en-ca/library/zk17ww08.aspx
+ * mingw32 headers say atexit is safe to use in shared libraries.
+ */
+# define HB_USE_ATEXIT 1
+# elif defined(__ANDROID__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6))
+/* This was fixed in Android NKD r8 or r8b:
+ * https://code.google.com/p/android/issues/detail?id=6455
+ * which introduced GCC 4.6:
+ * https://developer.android.com/tools/sdk/ndk/index.html
+ */
+# define HB_USE_ATEXIT 1
+# endif
+#endif
/* Basics */
