Add PL_shutdownhook

Author: Leont

embed.fnc

@@ -2353,6 +2353,7 @@ p	|void	|no_bareword_filehandle 				\
 				|NN const char *fhname
 Tefprv	|void	|noperl_die	|NN const char *pat			\
 				|...
+CGTdp	|void	|noshutdownhook
 Adp	|int	|nothreadhook
 p	|void	|notify_parser_that_encoding_changed
 : Used in perly.y

embed.h

@@ -452,6 +452,7 @@
 # define new_stackinfo(a,b)                     Perl_new_stackinfo(aTHX_ a,b)
 # define new_stackinfo_flags(a,b,c)             Perl_new_stackinfo_flags(aTHX_ a,b,c)
 # define new_version(a)                         Perl_new_version(aTHX_ a)
+# define noshutdownhook                         Perl_noshutdownhook
 # define nothreadhook()                         Perl_nothreadhook(aTHX)
 # define op_append_elem(a,b,c)                  Perl_op_append_elem(aTHX_ a,b,c)
 # define op_append_list(a,b,c)                  Perl_op_append_list(aTHX_ a,b,c)

perl.c

@@ -480,6 +480,19 @@ Perl_nothreadhook(pTHX)
     return 0;
 }
 
+/*
+=for apidoc noshutdownhook
+
+Stub that provides shutdown hook.
+
+=cut
+*/
+
+void
+Perl_noshutdownhook()
+{
+}
+
 #ifdef DEBUG_LEAKING_SCALARS_FORK_DUMP
 void
 Perl_dump_sv_child(pTHX_ SV *sv)

perl.h

@@ -5350,6 +5350,7 @@ typedef int  (*thrhook_proc_t) (pTHX);
 typedef OP* (*PPADDR_t[]) (pTHX);
 typedef bool (*destroyable_proc_t) (pTHX_ SV *sv);
 typedef void (*despatch_signals_proc_t) (pTHX);
+typedef void (*shutdown_proc_t)();
 
 #if defined(__DYNAMIC__) && defined(PERL_DARWIN) && defined(PERL_CORE)
 #  include <crt_externs.h>	/* for the env array */

perlvars.h

@@ -380,6 +380,12 @@ PERLVAR(G, user_prop_mutex, perl_mutex)    /* Mutex for manipulating
                                               PL_user_defined_properties */
 #endif
 
+/* This hook is called during system termination (PERL_SYS_TERM).
+ * This is needed for tearing down threads::shared and probably
+ * not be used for anything else.
+ */
+PERLVARI(G, shutdownhook, shutdown_proc_t, &Perl_noshutdownhook);
+
 /* these record the best way to perform certain IO operations while
  * atomically setting FD_CLOEXEC. On the first call, a probe is done
  * and the result recorded for use by subsequent calls.