-#if defined __need_sig_atomic_t || defined __need_sigset_t
-/* Special invocation convention inside glibc header files. */
+#if defined __need_sig_atomic_t || defined __need_sigset_t || defined _GL_ALREADY_INCLUDING_SIGNAL_H || (defined _SIGNAL_H && !defined __SIZEOF_PTHREAD_MUTEX_T)
+/* Special invocation convention:
+ - Inside glibc header files.
+ - On glibc systems we have a sequence of nested includes
+ <signal.h> -> <ucontext.h> -> <signal.h>.
+ In this situation, the functions are not yet declared, therefore we cannot
+ provide the C++ aliases.
+ - On glibc systems with GCC 4.3 we have a sequence of nested includes
+ <csignal> -> </usr/include/signal.h> -> <sys/ucontext.h> -> <signal.h>.
+ In this situation, some of the functions are not yet declared, therefore
+ we cannot provide the C++ aliases. */