--- sysroot.orig/usr/include/sys/cdefs.h	2019-07-30 14:14:11.386945311 -0400
+++ sysroot/usr/include/sys/cdefs.h	2019-07-30 14:12:44.446936650 -0400
@@ -46,6 +46,18 @@
 #define __END_DECLS
 #endif
 
+/* GCC keyword fixes */
+#ifndef __has_builtin
+#   define __has_builtin(x) 0
+#endif
+#ifndef __has_feature
+#   define __has_feature(x) 0
+#endif
+#ifndef __clang__
+#  define _Nullable
+#  define _Nonnull
+#endif
+
 #define __strong_alias(alias, sym) \
     __asm__(".global " #alias "\n" \
             #alias " = " #sym);
@@ -176,7 +188,11 @@
  * _FILE_OFFSET_BITS 64 support.
  * See https://android.googlesource.com/platform/bionic/+/master/docs/32-bit-abi.md
  */
-#if !defined(__LP64__) && defined(_FILE_OFFSET_BITS) && _FILE_OFFSET_BITS == 64
+/* Using _FILE_OFFSET_BITS=64 does not work well on Android
+ * and can cause problems when mixing libraries, which is why
+ * Termux hides away this unless TERMUX_EXPOSE_FILE_OFFSET64
+ * is defined. */
+#if !defined(__LP64__) && defined(_FILE_OFFSET_BITS) && _FILE_OFFSET_BITS == 64 && defined(TERMUX_EXPOSE_FILE_OFFSET64)
 #  define __USE_FILE_OFFSET64 1
 /*
  * Note that __RENAME_IF_FILE_OFFSET64 is only valid if the off_t and off64_t
@@ -243,6 +259,14 @@
 #  endif
 #endif
 
+/* GCC does not fare well with fortify headers. */
+#if !defined(__clang__) && (defined(__BIONIC_FORTIFY) || defined(__BIONIC_DECLARE_FORTIFY_HELPERS))
+#   warning "Disabling _FORTIFY_SOURCE, it requires Clang."
+#   undef _FORTIFY_SOURCE
+#   undef __BIONIC_FORTIFY
+#   undef __BIONIC_DECLARE_FORTIFY_HEADERS
+#endif
+
 // As we move some FORTIFY checks to be always on, __bos needs to be
 // always available.
 #if defined(__BIONIC_FORTIFY)
@@ -292,7 +316,11 @@
 #  define __BIONIC_INCLUDE_FORTIFY_HEADERS 1
 #endif
 
-#define __overloadable __attribute__((overloadable))
+#ifdef __clang__
+#  define __overloadable __attribute__((overloadable))
+#else
+#  define __overloadable
+#endif
 
 /* Used to tag non-static symbols that are private and never exposed by the shared library. */
 #define __LIBC_HIDDEN__ __attribute__((visibility("hidden")))
@@ -310,7 +338,7 @@
 /* Used to rename functions so that the compiler emits a call to 'x' rather than the function this was applied to. */
 #define __RENAME(x) __asm__(#x)
 
-#if __has_builtin(__builtin_umul_overflow) || __GNUC__ >= 5
+#if __GNUC__ >= 5 || __has_builtin(__builtin_umul_overflow)
 #if defined(__LP64__)
 #define __size_mul_overflow(a, b, result) __builtin_umull_overflow(a, b, result)
 #else