-AS_IF([test "x$def_compiler_tls" = "xyes"], AC_DEFINE([CONFIG_RCU_TLS], [1]), [:])
+# Make sure the C compiler supports C99
+AS_IF([test "$ac_cv_prog_cc_c99" = "no"], [AC_MSG_ERROR([The compiler does not support C99])])
+
+# Enable available system extensions and LFS support
+AC_USE_SYSTEM_EXTENSIONS
+AC_SYS_LARGEFILE
+
+# Make sure the C compiler supports __attribute__
+AX_C___ATTRIBUTE__
+AS_IF([test "x$ax_cv___attribute__" != "xyes"],
+ [AC_MSG_ERROR([The compiler does not support __attribute__ extensions])])
+
+# Make sure we have pthread support
+AX_PTHREAD([], [AC_MSG_ERROR([Could not configure pthread support])])
+
+# Make sure the C compiler supports weak symbols
+AX_SYS_WEAK_ALIAS
+AS_IF([test "x$ax_cv_sys_weak_alias" = "xno"],
+ [AC_MSG_ERROR([Your platform doesn't support weak symbols.])])
+
+# Checks for typedefs, structures, and compiler characteristics.
+AC_C_INLINE
+AC_C_TYPEOF
+AC_TYPE_INT32_T
+AC_TYPE_PID_T
+AC_TYPE_SIZE_T
+AC_TYPE_SSIZE_T
+AC_TYPE_UINT16_T
+AC_TYPE_UINT32_T
+AC_TYPE_UINT64_T
+AC_TYPE_UINT8_T
+
+
+## ##
+## Header checks ##
+## ##
+
+AC_HEADER_STDBOOL
+AC_CHECK_HEADERS([ \
+ limits.h \
+ stddef.h \
+ sys/param.h \
+ sys/time.h \
+])
+
+
+## ##
+## Programs checks ##
+## ##