X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=perlio.c;h=9e06ef1856f50dc9c9b2fb8a4682fc2e8587be21;hb=51254d33a14eeacb273f244a97f13b86d9e56aa2;hp=86cc827ce5df5c47a44f9afb2561e1fe1cbbdb7c;hpb=93c2c2ecd9924225ba4c26762e3e59cf95458982;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/perlio.c b/perlio.c
index 86cc827..9e06ef1 100644
--- a/perlio.c
+++ b/perlio.c
@@ -1,5 +1,5 @@
 /*
- * perlio.c Copyright (c) 1996-2005, Nick Ing-Simmons You may distribute
+ * perlio.c Copyright (c) 1996-2006, Nick Ing-Simmons You may distribute
  * under the terms of either the GNU General Public License or the
  * Artistic License, as specified in the README file.
  */
@@ -30,7 +30,11 @@
 #ifdef PERL_MICRO
 #   include "uconfig.h"
 #else
-#   include "config.h"
+#   ifndef USE_CROSS_COMPILE
+#       include "config.h"
+#   else
+#       include "xconfig.h"
+#   endif
 #endif
 
 #define PERLIO_NOT_STDIO 0
@@ -56,8 +60,6 @@
 
 #include "XSUB.h"
 
-#define PERLIO_MAX_REFCOUNTABLE_FD 2048
-
 #ifdef __Lynx__
 /* Missing proto on LynxOS */
 int mkstemp(char*);
@@ -122,11 +124,11 @@ perlsio_binmode(FILE *fp, int iotype, int mode)
 #ifdef DOSISH
 #  if defined(atarist) || defined(__MINT__)
     if (!fflush(fp)) {
-	if (mode & O_BINARY)
-	    ((FILE *) fp)->_flag |= _IOBIN;
-	else
-	    ((FILE *) fp)->_flag &= ~_IOBIN;
-	return 1;
+        if (mode & O_BINARY)
+            ((FILE *) fp)->_flag |= _IOBIN;
+        else
+            ((FILE *) fp)->_flag &= ~_IOBIN;
+        return 1;
     }
     return 0;
 #  else
@@ -137,31 +139,34 @@ perlsio_binmode(FILE *fp, int iotype, int mode)
     if (PerlLIO_setmode(fileno(fp), mode) != -1) {
 #endif
 #    if defined(WIN32) && defined(__BORLANDC__)
-	/*
-	 * The translation mode of the stream is maintained independent of
-	 * the translation mode of the fd in the Borland RTL (heavy
-	 * digging through their runtime sources reveal).  User has to set
-	 * the mode explicitly for the stream (though they don't document
-	 * this anywhere). GSAR 97-5-24
-	 */
-	fseek(fp, 0L, 0);
-	if (mode & O_BINARY)
-	    fp->flags |= _F_BIN;
-	else
-	    fp->flags &= ~_F_BIN;
+        /*
+         * The translation mode of the stream is maintained independent 
+of
+         * the translation mode of the fd in the Borland RTL (heavy
+         * digging through their runtime sources reveal).  User has to 
+set
+         * the mode explicitly for the stream (though they don't 
+document
+         * this anywhere). GSAR 97-5-24
+         */
+        fseek(fp, 0L, 0);
+        if (mode & O_BINARY)
+            fp->flags |= _F_BIN;
+        else
+            fp->flags &= ~_F_BIN;
 #    endif
-	return 1;
+        return 1;
     }
     else
-	return 0;
+        return 0;
 #  endif
 #else
 #  if defined(USEMYBINMODE)
     dTHX;
     if (my_binmode(fp, iotype, mode) != FALSE)
-	return 1;
+        return 1;
     else
-	return 0;
+        return 0;
 #  else
     PERL_UNUSED_ARG(fp);
     PERL_UNUSED_ARG(iotype);
@@ -260,7 +265,7 @@ PerlIO_binmode(pTHX_ PerlIO *fp, int iotype, int mode, const char *names)
 PerlIO *
 PerlIO_fdupopen(pTHX_ PerlIO *f, CLONE_PARAMS *param, int flags)
 {
-#if defined(PERL_MICRO) || defined(SYMBIAN)
+#if defined(PERL_MICRO) || defined(__SYMBIAN32__)
     return NULL;
 #else
 #ifdef PERL_IMPLICIT_SYS
@@ -273,9 +278,10 @@ PerlIO_fdupopen(pTHX_ PerlIO *f, CLONE_PARAMS *param, int flags)
 	const int fd = PerlLIO_dup(PerlIO_fileno(f));
 	if (fd >= 0) {
 	    char mode[8];
-	    int omode = fcntl(fd, F_GETFL);
 #ifdef DJGPP
-	    omode = djgpp_get_stream_mode(f);
+	    const int omode = djgpp_get_stream_mode(f);
+#else
+	    const int omode = fcntl(fd, F_GETFL);
 #endif
 	    PerlIO_intmode2str(omode,mode,NULL);
 	    /* the r+ is a hack */
@@ -334,7 +340,7 @@ XS(XS_PerlIO__Layer__find)
     if (items < 2)
 	Perl_croak(aTHX_ "Usage class->find(name[,load])");
     else {
-	const char *name = SvPV_nolen_const(ST(1));
+	const char * const name = SvPV_nolen_const(ST(1));
 	ST(0) = (strEQ(name, "crlf")
 		 || strEQ(name, "raw")) ? &PL_sv_yes : &PL_sv_undef;
 	XSRETURN(1);
@@ -356,6 +362,7 @@ Perl_boot_core_PerlIO(pTHX)
 void
 PerlIO_init(pTHX)
 {
+    PERL_UNUSED_CONTEXT;
     /*
      * Does nothing (yet) except force this file to be included in perl
      * binary. That allows this file to force inclusion of other functions
@@ -393,6 +400,7 @@ PerlIO_tmpfile(void)
 void
 PerlIO_init(pTHX)
 {
+    PERL_UNUSED_CONTEXT;
     /*
      * Force this file to be included in perl binary. Which allows this
      * file to force inclusion of other functions that may be required by
@@ -458,7 +466,7 @@ PerlIO_debug(const char *fmt, ...)
     dSYS;
     va_start(ap, fmt);
     if (!PL_perlio_debug_fd && !PL_tainting && PL_uid == PL_euid && PL_gid == PL_egid) {
-        const char *s = PerlEnv_getenv("PERLIO_DEBUG");
+	const char * const s = PerlEnv_getenv("PERLIO_DEBUG");
 	if (s && *s)
 	    PL_perlio_debug_fd = PerlLIO_open3(s, O_WRONLY | O_CREAT | O_APPEND, 0666);
 	else
@@ -466,21 +474,18 @@ PerlIO_debug(const char *fmt, ...)
     }
     if (PL_perlio_debug_fd > 0) {
 	dTHX;
-	const char *s = CopFILE(PL_curcop);
-	STRLEN len;
 #ifdef USE_ITHREADS
+	const char * const s = CopFILE(PL_curcop);
 	/* Use fixed buffer as sv_catpvf etc. needs SVs */
 	char buffer[1024];
-	if (!s)
-	    s = "(none)";
-	len = sprintf(buffer, "%.40s:%" IVdf " ", s, (IV) CopLINE(PL_curcop));
-	vsprintf(buffer+len, fmt, ap);
-	PerlLIO_write(PL_perlio_debug_fd, buffer, strlen(buffer));
+	const STRLEN len = my_sprintf(buffer, "%.40s:%" IVdf " ", s ? s : "(none)", (IV) CopLINE(PL_curcop));
+	const STRLEN len2 = my_vsnprintf(buffer+len, sizeof(buffer) - len, fmt, ap);
+	PerlLIO_write(PL_perlio_debug_fd, buffer, len + len2);
 #else
-	SV *sv = newSVpvn("", 0);
-	if (!s)
-	    s = "(none)";
-	Perl_sv_catpvf(aTHX_ sv, "%s:%" IVdf " ", s,
+	const char *s = CopFILE(PL_curcop);
+	STRLEN len;
+	SV * const sv = newSVpvs("");
+	Perl_sv_catpvf(aTHX_ sv, "%s:%" IVdf " ", s ? s : "(none)",
 		       (IV) CopLINE(PL_curcop));
 	Perl_sv_vcatpvf(aTHX_ sv, fmt, &ap);
 
@@ -506,6 +511,7 @@ PerlIO_debug(const char *fmt, ...)
 PerlIO *
 PerlIO_allocate(pTHX)
 {
+    dVAR;
     /*
      * Find a free slot in the table, allocating new table as necessary
      */
@@ -551,12 +557,12 @@ PerlIO_fdupopen(pTHX_ PerlIO *f, CLONE_PARAMS *param, int flags)
 void
 PerlIO_cleantable(pTHX_ PerlIO **tablep)
 {
-    PerlIO *table = *tablep;
+    PerlIO * const table = *tablep;
     if (table) {
 	int i;
 	PerlIO_cleantable(aTHX_(PerlIO **) & (table[0]));
 	for (i = PERLIO_TABLE_SIZE - 1; i > 0; i--) {
-	    PerlIO *f = table + i;
+	    PerlIO * const f = table + i;
 	    if (*f) {
 		PerlIO_close(f);
 	    }
@@ -571,6 +577,7 @@ PerlIO_list_t *
 PerlIO_list_alloc(pTHX)
 {
     PerlIO_list_t *list;
+    PERL_UNUSED_CONTEXT;
     Newxz(list, 1, PerlIO_list_t);
     list->refcnt = 1;
     return list;
@@ -597,7 +604,10 @@ PerlIO_list_free(pTHX_ PerlIO_list_t *list)
 void
 PerlIO_list_push(pTHX_ PerlIO_list_t *list, PerlIO_funcs *funcs, SV *arg)
 {
+    dVAR;
     PerlIO_pair_t *p;
+    PERL_UNUSED_CONTEXT;
+
     if (list->cur >= list->len) {
 	list->len += 8;
 	if (list->array)
@@ -608,19 +618,19 @@ PerlIO_list_push(pTHX_ PerlIO_list_t *list, PerlIO_funcs *funcs, SV *arg)
     p = &(list->array[list->cur++]);
     p->funcs = funcs;
     if ((p->arg = arg)) {
-	(void)SvREFCNT_inc(arg);
+	SvREFCNT_inc_simple_void_NN(arg);
     }
 }
 
 PerlIO_list_t *
 PerlIO_clone_list(pTHX_ PerlIO_list_t *proto, CLONE_PARAMS *param)
 {
-    PerlIO_list_t *list = (PerlIO_list_t *) NULL;
+    PerlIO_list_t *list = NULL;
     if (proto) {
 	int i;
 	list = PerlIO_list_alloc(aTHX);
 	for (i=0; i < proto->cur; i++) {
-	    SV *arg = Nullsv;
+	    SV *arg = NULL;
 	    if (proto->array[i].arg)
 		arg = PerlIO_sv_dup(aTHX_ proto->array[i].arg,param);
 	    PerlIO_list_push(aTHX_ list, proto->array[i].funcs, arg);
@@ -639,7 +649,7 @@ PerlIO_clone(pTHX_ PerlInterpreter *proto, CLONE_PARAMS *param)
     PL_known_layers = PerlIO_clone_list(aTHX_ proto->Iknown_layers, param);
     PL_def_layerlist = PerlIO_clone_list(aTHX_ proto->Idef_layerlist, param);
     PerlIO_allocate(aTHX); /* root slot is never used */
-    PerlIO_debug("Clone %p from %p\n",aTHX,proto);
+    PerlIO_debug("Clone %p from %p\n",(void*)aTHX,(void*)proto);
     while ((f = *table)) {
 	    int i;
 	    table = (PerlIO **) (f++);
@@ -651,6 +661,7 @@ PerlIO_clone(pTHX_ PerlInterpreter *proto, CLONE_PARAMS *param)
 	    }
 	}
 #else
+    PERL_UNUSED_CONTEXT;
     PERL_UNUSED_ARG(proto);
     PERL_UNUSED_ARG(param);
 #endif
@@ -659,17 +670,18 @@ PerlIO_clone(pTHX_ PerlInterpreter *proto, CLONE_PARAMS *param)
 void
 PerlIO_destruct(pTHX)
 {
+    dVAR;
     PerlIO **table = &PL_perlio;
     PerlIO *f;
 #ifdef USE_ITHREADS
-    PerlIO_debug("Destruct %p\n",aTHX);
+    PerlIO_debug("Destruct %p\n",(void*)aTHX);
 #endif
     while ((f = *table)) {
 	int i;
 	table = (PerlIO **) (f++);
 	for (i = 1; i < PERLIO_TABLE_SIZE; i++) {
 	    PerlIO *x = f;
-	    PerlIOl *l;
+	    const PerlIOl *l;
 	    while ((l = *x)) {
 		if (l->tab->kind & PERLIO_K_DESTRUCT) {
 		    PerlIO_debug("Destruct popping %s\n", l->tab->name);
@@ -688,7 +700,7 @@ PerlIO_destruct(pTHX)
 void
 PerlIO_pop(pTHX_ PerlIO *f)
 {
-    PerlIOl *l = *f;
+    const PerlIOl *l = *f;
     if (l) {
 	PerlIO_debug("PerlIO_pop f=%p %s\n", (void*)f, l->tab->name);
 	if (l->tab->Popped) {
@@ -714,24 +726,25 @@ PerlIO_pop(pTHX_ PerlIO *f)
 AV *
 PerlIO_get_layers(pTHX_ PerlIO *f)
 {
-     AV *av = newAV();
+    dVAR;
+    AV * const av = newAV();
 
-     if (PerlIOValid(f)) {
-	  PerlIOl *l = PerlIOBase(f);
-
-	  while (l) {
-	       SV *name = l->tab && l->tab->name ?
-		    newSVpv(l->tab->name, 0) : &PL_sv_undef;
-	       SV *arg = l->tab && l->tab->Getarg ?
-		    (*l->tab->Getarg)(aTHX_ &l, 0, 0) : &PL_sv_undef;
-	       av_push(av, name);
-	       av_push(av, arg);
-	       av_push(av, newSViv((IV)l->flags));
-	       l = l->next;
-	  }
-     }
+    if (PerlIOValid(f)) {
+	PerlIOl *l = PerlIOBase(f);
+
+	while (l) {
+	    SV * const name = l->tab && l->tab->name ?
+	    newSVpv(l->tab->name, 0) : &PL_sv_undef;
+	    SV * const arg = l->tab && l->tab->Getarg ?
+	    (*l->tab->Getarg)(aTHX_ &l, 0, 0) : &PL_sv_undef;
+	    av_push(av, name);
+	    av_push(av, arg);
+	    av_push(av, newSViv((IV)l->flags));
+	    l = l->next;
+	}
+    }
 
-     return av;
+    return av;
 }
 
 /*--------------------------------------------------------------------------------------*/
@@ -759,21 +772,20 @@ PerlIO_find_layer(pTHX_ const char *name, STRLEN len, int load)
 	    Perl_croak(aTHX_ "Recursive call to Perl_load_module in PerlIO_find_layer");
 	    return NULL;
 	} else {
-	    SV * const pkgsv = newSVpvn("PerlIO", 6);
+	    SV * const pkgsv = newSVpvs("PerlIO");
 	    SV * const layer = newSVpvn(name, len);
 	    CV * const cv    = get_cv("PerlIO::Layer::NoWarnings", FALSE);
 	    ENTER;
 	    SAVEINT(PL_in_load_module);
 	    if (cv) {
 		SAVEGENERICSV(PL_warnhook);
-		(void)SvREFCNT_inc(cv);
-		PL_warnhook = (SV *) cv;
+		PL_warnhook = (SV *) (SvREFCNT_inc_simple_NN(cv));
 	    }
 	    PL_in_load_module++;
 	    /*
 	     * The two SVs are magically freed by load_module
 	     */
-	    Perl_load_module(aTHX_ 0, pkgsv, Nullsv, layer, Nullsv);
+	    Perl_load_module(aTHX_ 0, pkgsv, NULL, layer, NULL);
 	    PL_in_load_module--;
 	    LEAVE;
 	    return PerlIO_find_layer(aTHX_ name, len, 0);
@@ -789,9 +801,9 @@ static int
 perlio_mg_set(pTHX_ SV *sv, MAGIC *mg)
 {
     if (SvROK(sv)) {
-	IO *io = GvIOn((GV *) SvRV(sv));
-	PerlIO *ifp = IoIFP(io);
-	PerlIO *ofp = IoOFP(io);
+	IO * const io = GvIOn((GV *) SvRV(sv));
+	PerlIO * const ifp = IoIFP(io);
+	PerlIO * const ofp = IoOFP(io);
 	Perl_warn(aTHX_ "set %" SVf " %p %p %p", sv, io, ifp, ofp);
     }
     return 0;
@@ -801,9 +813,9 @@ static int
 perlio_mg_get(pTHX_ SV *sv, MAGIC *mg)
 {
     if (SvROK(sv)) {
-	IO *io = GvIOn((GV *) SvRV(sv));
-	PerlIO *ifp = IoIFP(io);
-	PerlIO *ofp = IoOFP(io);
+	IO * const io = GvIOn((GV *) SvRV(sv));
+	PerlIO * const ifp = IoIFP(io);
+	PerlIO * const ofp = IoOFP(io);
 	Perl_warn(aTHX_ "get %" SVf " %p %p %p", sv, io, ifp, ofp);
     }
     return 0;
@@ -834,8 +846,8 @@ MGVTBL perlio_vtab = {
 XS(XS_io_MODIFY_SCALAR_ATTRIBUTES)
 {
     dXSARGS;
-    SV *sv = SvRV(ST(1));
-    AV *av = newAV();
+    SV * const sv = SvRV(ST(1));
+    AV * const av = newAV();
     MAGIC *mg;
     int count = 0;
     int i;
@@ -847,10 +859,10 @@ XS(XS_io_MODIFY_SCALAR_ATTRIBUTES)
     Perl_warn(aTHX_ "attrib %" SVf, sv);
     for (i = 2; i < items; i++) {
 	STRLEN len;
-	const char *name = SvPV_const(ST(i), len);
-	SV *layer = PerlIO_find_layer(aTHX_ name, len, 1);
+	const char * const name = SvPV_const(ST(i), len);
+	SV * const layer = PerlIO_find_layer(aTHX_ name, len, 1);
 	if (layer) {
-	    av_push(av, SvREFCNT_inc(layer));
+	    av_push(av, SvREFCNT_inc_simple_NN(layer));
 	}
 	else {
 	    ST(count) = ST(i);
@@ -866,7 +878,7 @@ XS(XS_io_MODIFY_SCALAR_ATTRIBUTES)
 SV *
 PerlIO_tab_sv(pTHX_ PerlIO_funcs *tab)
 {
-    HV * const stash = gv_stashpv("PerlIO::Layer", TRUE);
+    HV * const stash = gv_stashpvs("PerlIO::Layer", TRUE);
     SV * const sv = sv_bless(newRV_noinc(newSViv(PTR2IV(tab))), stash);
     return sv;
 }
@@ -876,6 +888,7 @@ XS(XS_PerlIO__Layer__NoWarnings)
     /* This is used as a %SIG{__WARN__} handler to supress warnings
        during loading of layers.
      */
+    dVAR;
     dXSARGS;
     if (items)
     	PerlIO_debug("warning:%s\n",SvPV_nolen_const(ST(0)));
@@ -884,6 +897,7 @@ XS(XS_PerlIO__Layer__NoWarnings)
 
 XS(XS_PerlIO__Layer__find)
 {
+    dVAR;
     dXSARGS;
     if (items < 2)
 	Perl_croak(aTHX_ "Usage class->find(name[,load])");
@@ -902,15 +916,17 @@ XS(XS_PerlIO__Layer__find)
 void
 PerlIO_define_layer(pTHX_ PerlIO_funcs *tab)
 {
+    dVAR;
     if (!PL_known_layers)
 	PL_known_layers = PerlIO_list_alloc(aTHX);
-    PerlIO_list_push(aTHX_ PL_known_layers, tab, Nullsv);
+    PerlIO_list_push(aTHX_ PL_known_layers, tab, NULL);
     PerlIO_debug("define %s %p\n", tab->name, (void*)tab);
 }
 
 int
 PerlIO_parse_layers(pTHX_ PerlIO_list_t *av, const char *names)
 {
+    dVAR;
     if (names) {
 	const char *s = names;
 	while (*s) {
@@ -919,7 +935,7 @@ PerlIO_parse_layers(pTHX_ PerlIO_list_t *av, const char *names)
 	    if (*s) {
 		STRLEN llen = 0;
 		const char *e = s;
-		const char *as = Nullch;
+		const char *as = NULL;
 		STRLEN alen = 0;
 		if (!isIDFIRST(*s)) {
 		    /*
@@ -1004,6 +1020,7 @@ PerlIO_parse_layers(pTHX_ PerlIO_list_t *av, const char *names)
 void
 PerlIO_default_buffer(pTHX_ PerlIO_list_t *av)
 {
+    dVAR;
     PERLIO_FUNCS_DECL(*tab) = &PerlIO_perlio;
 #ifdef PERLIO_USING_CRLF
     tab = &PerlIO_crlf;
@@ -1083,8 +1100,9 @@ PERLIO_FUNCS_DECL(PerlIO_remove) = {
 PerlIO_list_t *
 PerlIO_default_layers(pTHX)
 {
+    dVAR;
     if (!PL_def_layerlist) {
-	const char *s = (PL_tainting) ? Nullch : PerlEnv_getenv("PERLIO");
+	const char * const s = (PL_tainting) ? NULL : PerlEnv_getenv("PERLIO");
 	PERLIO_FUNCS_DECL(*osLayer) = &PerlIO_unix;
 	PL_def_layerlist = PerlIO_list_alloc(aTHX);
 	PerlIO_define_layer(aTHX_ PERLIO_FUNCS_CAST(&PerlIO_unix));
@@ -1134,6 +1152,7 @@ Perl_boot_core_PerlIO(pTHX)
 PerlIO_funcs *
 PerlIO_default_layer(pTHX_ I32 n)
 {
+    dVAR;
     PerlIO_list_t * const av = PerlIO_default_layers(aTHX);
     if (n < 0)
 	n += av->cur;
@@ -1146,6 +1165,7 @@ PerlIO_default_layer(pTHX_ I32 n)
 void
 PerlIO_stdstreams(pTHX)
 {
+    dVAR;
     if (!PL_perlio) {
 	PerlIO_allocate(aTHX);
 	PerlIO_fdopen(0, "Ir" PERLIO_STDTEXT);
@@ -1167,19 +1187,26 @@ PerlIO_push(pTHX_ PerlIO *f, PERLIO_FUNCS_DECL(*tab), const char *mode, SV *arg)
 	    goto mismatch;
 	}
 	/* Real layer with a data area */
-	Newxc(l,tab->size,char,PerlIOl);
-	if (l && f) {
-	    Zero(l, tab->size, char);
-	    l->next = *f;
-	    l->tab = (PerlIO_funcs*) tab;
-	    *f = l;
-	    PerlIO_debug("PerlIO_push f=%p %s %s %p\n", (void*)f, tab->name,
-			(mode) ? mode : "(Null)", (void*)arg);
-	    if (*l->tab->Pushed &&
-		(*l->tab->Pushed) (aTHX_ f, mode, arg, (PerlIO_funcs*) tab) != 0) {
-		PerlIO_pop(aTHX_ f);
-		return NULL;
+	if (f) {
+	    char *temp;
+	    Newxz(temp, tab->size, char);
+	    l = (PerlIOl*)temp;
+	    if (l) {
+		l->next = *f;
+		l->tab = (PerlIO_funcs*) tab;
+		*f = l;
+		PerlIO_debug("PerlIO_push f=%p %s %s %p\n",
+			     (void*)f, tab->name,
+			     (mode) ? mode : "(Null)", (void*)arg);
+		if (*l->tab->Pushed &&
+		    (*l->tab->Pushed)
+		      (aTHX_ f, mode, arg, (PerlIO_funcs*) tab) != 0) {
+		    PerlIO_pop(aTHX_ f);
+		    return NULL;
+		}
 	    }
+	    else
+		return NULL;
 	}
     }
     else if (f) {
@@ -1295,9 +1322,10 @@ PerlIO_apply_layers(pTHX_ PerlIO *f, const char *mode, const char *names)
 int
 PerlIO_binmode(pTHX_ PerlIO *f, int iotype, int mode, const char *names)
 {
-    PerlIO_debug("PerlIO_binmode f=%p %s %c %x %s\n",
-		 (void*)f, PerlIOBase(f)->tab->name, iotype, mode,
-		 (names) ? names : "(Null)");
+    PerlIO_debug("PerlIO_binmode f=%p %s %c %x %s\n", (void*)f,
+                 (PerlIOBase(f)) ? PerlIOBase(f)->tab->name : "(Null)",
+                 iotype, mode, (names) ? names : "(Null)");
+
     if (names) {
 	/* Do not flush etc. if (e.g.) switching encodings.
 	   if a pushed layer knows it needs to flush lower layers
@@ -1343,7 +1371,7 @@ PerlIO_binmode(pTHX_ PerlIO *f, int iotype, int mode, const char *names)
 	/* Legacy binmode is now _defined_ as being equivalent to pushing :raw
 	   So code that used to be here is now in PerlIORaw_pushed().
 	 */
-	return PerlIO_push(aTHX_ f, PERLIO_FUNCS_CAST(&PerlIO_raw), Nullch, Nullsv) ? TRUE : FALSE;
+	return PerlIO_push(aTHX_ f, PERLIO_FUNCS_CAST(&PerlIO_raw), NULL, NULL) ? TRUE : FALSE;
     }
 }
 
@@ -1376,18 +1404,20 @@ Perl_PerlIO_close(pTHX_ PerlIO *f)
 int
 Perl_PerlIO_fileno(pTHX_ PerlIO *f)
 {
+    dVAR;
      Perl_PerlIO_or_Base(f, Fileno, fileno, -1, (aTHX_ f));
 }
 
 static const char *
 PerlIO_context_layers(pTHX_ const char *mode)
 {
+    dVAR;
     const char *type = NULL;
     /*
      * Need to supply default layer info from open.pm
      */
     if (PL_curcop) {
-	SV *layers = PL_curcop->cop_io;
+	SV * const layers = PL_curcop->cop_io;
 	if (layers) {
 	    STRLEN len;
 	    type = SvPV_const(layers, len);
@@ -1395,7 +1425,7 @@ PerlIO_context_layers(pTHX_ const char *mode)
 		/*
 		 * Skip to write part
 		 */
-		const char *s = strchr(type, 0);
+		const char * const s = strchr(type, 0);
 		if (s && (STRLEN)(s - type) < len) {
 		    type = s + 1;
 		}
@@ -1408,24 +1438,25 @@ PerlIO_context_layers(pTHX_ const char *mode)
 static PerlIO_funcs *
 PerlIO_layer_from_ref(pTHX_ SV *sv)
 {
+    dVAR;
     /*
      * For any scalar type load the handler which is bundled with perl
      */
     if (SvTYPE(sv) < SVt_PVAV)
-	return PerlIO_find_layer(aTHX_ "scalar", 6, 1);
+	return PerlIO_find_layer(aTHX_ STR_WITH_LEN("scalar"), 1);
 
     /*
      * For other types allow if layer is known but don't try and load it
      */
     switch (SvTYPE(sv)) {
     case SVt_PVAV:
-	return PerlIO_find_layer(aTHX_ "Array", 5, 0);
+	return PerlIO_find_layer(aTHX_ STR_WITH_LEN("Array"), 0);
     case SVt_PVHV:
-	return PerlIO_find_layer(aTHX_ "Hash", 4, 0);
+	return PerlIO_find_layer(aTHX_ STR_WITH_LEN("Hash"), 0);
     case SVt_PVCV:
-	return PerlIO_find_layer(aTHX_ "Code", 4, 0);
+	return PerlIO_find_layer(aTHX_ STR_WITH_LEN("Code"), 0);
     case SVt_PVGV:
-	return PerlIO_find_layer(aTHX_ "Glob", 4, 0);
+	return PerlIO_find_layer(aTHX_ STR_WITH_LEN("Glob"), 0);
     }
     return NULL;
 }
@@ -1434,12 +1465,13 @@ PerlIO_list_t *
 PerlIO_resolve_layers(pTHX_ const char *layers,
 		      const char *mode, int narg, SV **args)
 {
+    dVAR;
     PerlIO_list_t *def = PerlIO_default_layers(aTHX);
     int incdef = 1;
     if (!PL_perlio)
 	PerlIO_stdstreams(aTHX);
     if (narg) {
-	SV *arg = *args;
+	SV * const arg = *args;
 	/*
 	 * If it is a reference but not an object see if we have a handler
 	 * for it
@@ -1458,7 +1490,7 @@ PerlIO_resolve_layers(pTHX_ const char *layers,
 	     */
 	}
     }
-    if (!layers)
+    if (!layers || !*layers)
 	layers = PerlIO_context_layers(aTHX_ mode);
     if (layers && *layers) {
 	PerlIO_list_t *av;
@@ -1478,7 +1510,7 @@ PerlIO_resolve_layers(pTHX_ const char *layers,
 	}
 	else {
 	    PerlIO_list_free(aTHX_ av);
-	    return (PerlIO_list_t *) NULL;
+	    return NULL;
 	}
     }
     else {
@@ -1492,9 +1524,10 @@ PerlIO *
 PerlIO_openn(pTHX_ const char *layers, const char *mode, int fd,
 	     int imode, int perm, PerlIO *f, int narg, SV **args)
 {
+    dVAR;
     if (!f && narg == 1 && *args == &PL_sv_undef) {
 	if ((f = PerlIO_tmpfile())) {
-	    if (!layers)
+	    if (!layers || !*layers)
 		layers = PerlIO_context_layers(aTHX_ mode);
 	    if (layers && *layers)
 		PerlIO_apply_layers(aTHX_ f, mode, layers);
@@ -1545,8 +1578,8 @@ PerlIO_openn(pTHX_ const char *layers, const char *mode, int fd,
 		Perl_croak(aTHX_ "More than one argument to open(,':%s')",tab->name);
 	    }
 	    PerlIO_debug("openn(%s,'%s','%s',%d,%x,%o,%p,%d,%p)\n",
-			 tab->name, layers, mode, fd, imode, perm,
-			 (void*)f, narg, (void*)args);
+			 tab->name, layers ? layers : "(Null)", mode, fd,
+			 imode, perm, (void*)f, narg, (void*)args);
 	    if (tab->Open)
 		 f = (*tab->Open) (aTHX_ tab, layera, n, mode, fd, imode, perm,
 				   f, narg, args);
@@ -1607,6 +1640,7 @@ Perl_PerlIO_tell(pTHX_ PerlIO *f)
 int
 Perl_PerlIO_flush(pTHX_ PerlIO *f)
 {
+    dVAR;
     if (f) {
 	if (*f) {
 	    const PerlIO_funcs *tab = PerlIOBase(f)->tab;
@@ -1648,6 +1682,7 @@ Perl_PerlIO_flush(pTHX_ PerlIO *f)
 void
 PerlIOBase_flush_linebuf(pTHX)
 {
+    dVAR;
     PerlIO **table = &PL_perlio;
     PerlIO *f;
     while ((f = *table)) {
@@ -1814,6 +1849,7 @@ Perl_PerlIO_set_ptrcnt(pTHX_ PerlIO *f, STDCHAR * ptr, int cnt)
 IV
 PerlIOUtf8_pushed(pTHX_ PerlIO *f, const char *mode, SV *arg, PerlIO_funcs *tab)
 {
+    PERL_UNUSED_CONTEXT;
     PERL_UNUSED_ARG(mode);
     PERL_UNUSED_ARG(arg);
     if (PerlIOValid(f)) {
@@ -1981,6 +2017,7 @@ IV
 PerlIOBase_pushed(pTHX_ PerlIO *f, const char *mode, SV *arg, PerlIO_funcs *tab)
 {
     PerlIOl * const l = PerlIOBase(f);
+    PERL_UNUSED_CONTEXT;
     PERL_UNUSED_ARG(arg);
 
     l->flags &= ~(PERLIO_F_CANREAD | PERLIO_F_CANWRITE |
@@ -2039,6 +2076,7 @@ PerlIOBase_pushed(pTHX_ PerlIO *f, const char *mode, SV *arg, PerlIO_funcs *tab)
 IV
 PerlIOBase_popped(pTHX_ PerlIO *f)
 {
+    PERL_UNUSED_CONTEXT;
     PERL_UNUSED_ARG(f);
     return 0;
 }
@@ -2050,7 +2088,7 @@ PerlIOBase_unread(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
      * Save the position as current head considers it
      */
     const Off_t old = PerlIO_tell(f);
-    PerlIO_push(aTHX_ f, PERLIO_FUNCS_CAST(&PerlIO_pending), "r", Nullsv);
+    PerlIO_push(aTHX_ f, PERLIO_FUNCS_CAST(&PerlIO_pending), "r", NULL);
     PerlIOSelf(f, PerlIOBuf)->posn = old;
     return PerlIOBuf_unread(aTHX_ f, vbuf, count);
 }
@@ -2071,7 +2109,7 @@ PerlIOBase_read(pTHX_ PerlIO *f, void *vbuf, Size_t count)
 	    SSize_t avail = PerlIO_get_cnt(f);
 	    SSize_t take = 0;
 	    if (avail > 0)
-		take = ((SSize_t)count < avail) ? count : avail;
+		take = ((SSize_t)count < avail) ? (SSize_t)count : avail;
 	    if (take > 0) {
 		STDCHAR *ptr = PerlIO_get_ptr(f);
 		Copy(ptr, buf, take, STDCHAR);
@@ -2095,6 +2133,7 @@ PerlIOBase_read(pTHX_ PerlIO *f, void *vbuf, Size_t count)
 IV
 PerlIOBase_noop_ok(pTHX_ PerlIO *f)
 {
+    PERL_UNUSED_CONTEXT;
     PERL_UNUSED_ARG(f);
     return 0;
 }
@@ -2102,6 +2141,7 @@ PerlIOBase_noop_ok(pTHX_ PerlIO *f)
 IV
 PerlIOBase_noop_fail(pTHX_ PerlIO *f)
 {
+    PERL_UNUSED_CONTEXT;
     PERL_UNUSED_ARG(f);
     return -1;
 }
@@ -2138,6 +2178,7 @@ PerlIOBase_close(pTHX_ PerlIO *f)
 IV
 PerlIOBase_eof(pTHX_ PerlIO *f)
 {
+    PERL_UNUSED_CONTEXT;
     if (PerlIOValid(f)) {
 	return (PerlIOBase(f)->flags & PERLIO_F_EOF) != 0;
     }
@@ -2147,6 +2188,7 @@ PerlIOBase_eof(pTHX_ PerlIO *f)
 IV
 PerlIOBase_error(pTHX_ PerlIO *f)
 {
+    PERL_UNUSED_CONTEXT;
     if (PerlIOValid(f)) {
 	return (PerlIOBase(f)->flags & PERLIO_F_ERROR) != 0;
     }
@@ -2157,7 +2199,7 @@ void
 PerlIOBase_clearerr(pTHX_ PerlIO *f)
 {
     if (PerlIOValid(f)) {
-	PerlIO *n = PerlIONext(f);
+	PerlIO * const n = PerlIONext(f);
 	PerlIOBase(f)->flags &= ~(PERLIO_F_ERROR | PERLIO_F_EOF);
 	if (PerlIOValid(n))
 	    PerlIO_clearerr(n);
@@ -2167,6 +2209,7 @@ PerlIOBase_clearerr(pTHX_ PerlIO *f)
 void
 PerlIOBase_setlinebuf(pTHX_ PerlIO *f)
 {
+    PERL_UNUSED_CONTEXT;
     if (PerlIOValid(f)) {
 	PerlIOBase(f)->flags |= PERLIO_F_LINEBUF;
     }
@@ -2176,7 +2219,7 @@ SV *
 PerlIO_sv_dup(pTHX_ SV *arg, CLONE_PARAMS *param)
 {
     if (!arg)
-	return Nullsv;
+	return NULL;
 #ifdef sv_dup
     if (param) {
 	return sv_dup(arg, param);
@@ -2202,7 +2245,7 @@ PerlIOBase_dup(pTHX_ PerlIO *f, PerlIO *o, CLONE_PARAMS *param, int flags)
 	    f = PerlIOBase_dup(aTHX_ f, nexto, param, flags);
     }
     if (f) {
-	PerlIO_funcs *self = PerlIOBase(o)->tab;
+	PerlIO_funcs * const self = PerlIOBase(o)->tab;
 	SV *arg;
 	char buf[8];
 	PerlIO_debug("PerlIOBase_dup %s f=%p o=%p param=%p\n",
@@ -2210,7 +2253,7 @@ PerlIOBase_dup(pTHX_ PerlIO *f, PerlIO *o, CLONE_PARAMS *param, int flags)
 	if (self->Getarg)
 	    arg = (*self->Getarg)(aTHX_ o, param, flags);
 	else {
-	    arg = Nullsv;
+	    arg = NULL;
 	}
 	f = PerlIO_push(aTHX_ f, self, PerlIO_modestr(o,buf), arg);
 	if (arg) {
@@ -2226,12 +2269,55 @@ perl_mutex PerlIO_mutex;
 
 /* PL_perlio_fd_refcnt[] is in intrpvar.h */
 
+/* Must be called with PerlIO_mutex locked.  */
+static void
+S_more_refcounted_fds(pTHX_ const int new_fd) {
+    dVAR;
+    const int old_max = PL_perlio_fd_refcnt_size;
+    const int new_max = 16 + (new_fd & ~15);
+    int *new_array;
+
+    PerlIO_debug("More fds - old=%d, need %d, new=%d\n",
+		 old_max, new_fd, new_max);
+
+    if (new_fd < old_max) {
+	return;
+    }
+
+    assert (new_max > new_fd);
+
+    new_array
+	= PerlMemShared_realloc(PL_perlio_fd_refcnt, new_max * sizeof(int));
+
+    if (!new_array) {
+#ifdef USE_THREADS
+	MUTEX_UNLOCK(&PerlIO_mutex);
+#endif
+	/* Can't use PerlIO to write as it allocates memory */
+	PerlLIO_write(PerlIO_fileno(Perl_error_log),
+		      PL_no_mem, strlen(PL_no_mem));
+	my_exit(1);
+    }
+
+    PL_perlio_fd_refcnt_size = new_max;
+    PL_perlio_fd_refcnt = new_array;
+
+    PerlIO_debug("Zeroing %p, %d\n",
+		 (void*)(new_array + old_max),
+		 new_max - old_max);
+
+    Zero(new_array + old_max, new_max - old_max, int);
+}
+
+
 void
 PerlIO_init(pTHX)
 {
  /* Place holder for stdstreams call ??? */
 #ifdef USE_THREADS
     MUTEX_INIT(&PerlIO_mutex);
+#else
+    PERL_UNUSED_CONTEXT;
 #endif
 }
 
@@ -2239,12 +2325,18 @@ void
 PerlIOUnix_refcnt_inc(int fd)
 {
     dTHX;
-    if (fd >= 0 && fd < PERLIO_MAX_REFCOUNTABLE_FD) {
+    if (fd >= 0) {
+	dVAR;
+
 #ifdef USE_THREADS
 	MUTEX_LOCK(&PerlIO_mutex);
 #endif
+	if (fd >= PL_perlio_fd_refcnt_size)
+	    S_more_refcounted_fds(aTHX_ fd);
+
 	PL_perlio_fd_refcnt[fd]++;
 	PerlIO_debug("fd %d refcnt=%d\n",fd,PL_perlio_fd_refcnt[fd]);
+
 #ifdef USE_THREADS
 	MUTEX_UNLOCK(&PerlIO_mutex);
 #endif
@@ -2256,10 +2348,16 @@ PerlIOUnix_refcnt_dec(int fd)
 {
     dTHX;
     int cnt = 0;
-    if (fd >= 0 && fd < PERLIO_MAX_REFCOUNTABLE_FD) {
+    if (fd >= 0) {
+	dVAR;
 #ifdef USE_THREADS
 	MUTEX_LOCK(&PerlIO_mutex);
 #endif
+	/* XXX should this be a panic?  */
+	if (fd >= PL_perlio_fd_refcnt_size)
+	    S_more_refcounted_fds(aTHX_ fd);
+
+	/* XXX should this be a panic if it drops below 0?  */
 	cnt = --PL_perlio_fd_refcnt[fd];
 	PerlIO_debug("fd %d refcnt=%d\n",fd,cnt);
 #ifdef USE_THREADS
@@ -2272,9 +2370,10 @@ PerlIOUnix_refcnt_dec(int fd)
 void
 PerlIO_cleanup(pTHX)
 {
+    dVAR;
     int i;
 #ifdef USE_ITHREADS
-    PerlIO_debug("Cleanup layers for %p\n",aTHX);
+    PerlIO_debug("Cleanup layers for %p\n",(void*)aTHX);
 #else
     PerlIO_debug("Cleanup layers\n");
 #endif
@@ -2368,6 +2467,7 @@ PerlIOUnix_oflags(const char *mode)
 IV
 PerlIOUnix_fileno(pTHX_ PerlIO *f)
 {
+    PERL_UNUSED_CONTEXT;
     return PerlIOSelf(f, PerlIOUnix)->fd;
 }
 
@@ -2390,6 +2490,7 @@ PerlIOUnix_setfd(pTHX_ PerlIO *f, int fd, int imode)
     s->fd = fd;
     s->oflags = imode;
     PerlIOUnix_refcnt_inc(fd);
+    PERL_UNUSED_CONTEXT;
 }
 
 IV
@@ -2417,6 +2518,7 @@ PerlIOUnix_seek(pTHX_ PerlIO *f, Off_t offset, int whence)
 {
     const int fd = PerlIOSelf(f, PerlIOUnix)->fd;
     Off_t new_loc;
+    PERL_UNUSED_CONTEXT;
     if (PerlIOBase(f)->flags & PERLIO_F_NOTREG) {
 #ifdef  ESPIPE
 	SETERRNO(ESPIPE, LIB_INVARG);
@@ -2427,9 +2529,7 @@ PerlIOUnix_seek(pTHX_ PerlIO *f, Off_t offset, int whence)
     }
     new_loc = PerlLIO_lseek(fd, offset, whence);
     if (new_loc == (Off_t) - 1)
-     {
-      return -1;
-     }
+	return -1;
     PerlIOBase(f)->flags &= ~PERLIO_F_EOF;
     return  0;
 }
@@ -2474,6 +2574,7 @@ PerlIOUnix_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
     }
     else {
 	if (f) {
+	    NOOP;
 	    /*
 	     * FIXME: pop layers ???
 	     */
@@ -2485,12 +2586,12 @@ PerlIOUnix_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
 PerlIO *
 PerlIOUnix_dup(pTHX_ PerlIO *f, PerlIO *o, CLONE_PARAMS *param, int flags)
 {
-    PerlIOUnix *os = PerlIOSelf(o, PerlIOUnix);
+    const PerlIOUnix * const os = PerlIOSelf(o, PerlIOUnix);
     int fd = os->fd;
     if (flags & PERLIO_DUP_FD) {
 	fd = PerlLIO_dup(fd);
     }
-    if (fd >= 0 && fd < PERLIO_MAX_REFCOUNTABLE_FD) {
+    if (fd >= 0) {
 	f = PerlIOBase_dup(aTHX_ f, o, param, flags);
 	if (f) {
 	    /* If all went well overwrite fd in dup'ed lay with the dup()'ed fd */
@@ -2505,6 +2606,7 @@ PerlIOUnix_dup(pTHX_ PerlIO *f, PerlIO *o, CLONE_PARAMS *param, int flags)
 SSize_t
 PerlIOUnix_read(pTHX_ PerlIO *f, void *vbuf, Size_t count)
 {
+    dVAR;
     const int fd = PerlIOSelf(f, PerlIOUnix)->fd;
 #ifdef PERLIO_STD_SPECIAL
     if (fd == 0)
@@ -2536,6 +2638,7 @@ PerlIOUnix_read(pTHX_ PerlIO *f, void *vbuf, Size_t count)
 SSize_t
 PerlIOUnix_write(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 {
+    dVAR;
     const int fd = PerlIOSelf(f, PerlIOUnix)->fd;
 #ifdef PERLIO_STD_SPECIAL
     if (fd == 1 || fd == 2)
@@ -2559,6 +2662,8 @@ PerlIOUnix_write(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 Off_t
 PerlIOUnix_tell(pTHX_ PerlIO *f)
 {
+    PERL_UNUSED_CONTEXT;
+
     return PerlLIO_lseek(PerlIOSelf(f, PerlIOUnix)->fd, 0, SEEK_CUR);
 }
 
@@ -2566,6 +2671,7 @@ PerlIOUnix_tell(pTHX_ PerlIO *f)
 IV
 PerlIOUnix_close(pTHX_ PerlIO *f)
 {
+    dVAR;
     const int fd = PerlIOSelf(f, PerlIOUnix)->fd;
     int code = 0;
     if (PerlIOBase(f)->flags & PERLIO_F_OPEN) {
@@ -2643,9 +2749,12 @@ typedef struct {
 IV
 PerlIOStdio_fileno(pTHX_ PerlIO *f)
 {
-    FILE *s;
-    if (PerlIOValid(f) && (s = PerlIOSelf(f, PerlIOStdio)->stdio)) {
-	return PerlSIO_fileno(s);
+    PERL_UNUSED_CONTEXT;
+
+    if (PerlIOValid(f)) {
+	FILE * const s = PerlIOSelf(f, PerlIOStdio)->stdio;
+	if (s)
+	    return PerlSIO_fileno(s);
     }
     errno = EBADF;
     return -1;
@@ -2726,7 +2835,7 @@ PerlIO_importFILE(FILE *stdio, const char *mode)
 	    }
 	    fclose(f2);
 	}
-	if ((f = PerlIO_push(aTHX_(f = PerlIO_allocate(aTHX)), PERLIO_FUNCS_CAST(&PerlIO_stdio), mode, Nullsv))) {
+	if ((f = PerlIO_push(aTHX_(f = PerlIO_allocate(aTHX)), PERLIO_FUNCS_CAST(&PerlIO_stdio), mode, NULL))) {
 	    s = PerlIOSelf(f, PerlIOStdio);
 	    s->stdio = stdio;
 	}
@@ -2741,8 +2850,8 @@ PerlIOStdio_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
 {
     char tmode[8];
     if (PerlIOValid(f)) {
-	const char *path = SvPV_nolen_const(*args);
-	PerlIOStdio *s = PerlIOSelf(f, PerlIOStdio);
+	const char * const path = SvPV_nolen_const(*args);
+	PerlIOStdio * const s = PerlIOSelf(f, PerlIOStdio);
 	FILE *stdio;
 	PerlIOUnix_refcnt_dec(fileno(s->stdio));
 	stdio = PerlSIO_freopen(path, (mode = PerlIOStdio_mode(mode, tmode)),
@@ -2755,7 +2864,7 @@ PerlIOStdio_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
     }
     else {
 	if (narg > 0) {
-	    const char *path = SvPV_nolen_const(*args);
+	    const char * const path = SvPV_nolen_const(*args);
 	    if (*mode == IoTYPE_NUMERIC) {
 		mode++;
 		fd = PerlLIO_open3(path, imode, perm);
@@ -2770,7 +2879,6 @@ PerlIOStdio_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
 #endif
 		stdio = PerlSIO_fopen(path, mode);
 		if (stdio) {
-		    PerlIOStdio *s;
 		    if (!f) {
 			f = PerlIO_allocate(aTHX);
 		    }
@@ -2778,9 +2886,10 @@ PerlIOStdio_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
 		        mode = PerlIOStdio_mode(mode, tmode);
 		    f = PerlIO_push(aTHX_ f, self, mode, PerlIOArg);
 		    if (f) {
-			s = PerlIOSelf(f, PerlIOStdio);
-			s->stdio = stdio;
-			PerlIOUnix_refcnt_inc(fileno(s->stdio));
+			PerlIOSelf(f, PerlIOStdio)->stdio = stdio;
+			PerlIOUnix_refcnt_inc(fileno(stdio));
+		    } else {
+			PerlSIO_fclose(stdio);
 		    }
 		    return f;
 		}
@@ -2818,9 +2927,8 @@ PerlIOStdio_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
 		    f = PerlIO_allocate(aTHX);
 		}
 		if ((f = PerlIO_push(aTHX_ f, self, mode, PerlIOArg))) {
-		    PerlIOStdio *s = PerlIOSelf(f, PerlIOStdio);
-		    s->stdio = stdio;
-		    PerlIOUnix_refcnt_inc(fileno(s->stdio));
+		    PerlIOSelf(f, PerlIOStdio)->stdio = stdio;
+		    PerlIOUnix_refcnt_inc(fileno(stdio));
 		}
 		return f;
 	    }
@@ -2846,6 +2954,7 @@ PerlIOStdio_dup(pTHX_ PerlIO *f, PerlIO *o, CLONE_PARAMS *param, int flags)
 		goto set_this;
 	    }
 	    else {
+		NOOP;
 		/* FIXME: To avoid messy error recovery if dup fails
 		   re-use the existing stdio as though flag was not set
 		 */
@@ -2862,6 +2971,8 @@ PerlIOStdio_dup(pTHX_ PerlIO *f, PerlIO *o, CLONE_PARAMS *param, int flags)
 static int
 PerlIOStdio_invalidate_fileno(pTHX_ FILE *f)
 {
+    PERL_UNUSED_CONTEXT;
+
     /* XXX this could use PerlIO_canset_fileno() and
      * PerlIO_set_fileno() support from Configure
      */
@@ -2876,31 +2987,7 @@ PerlIOStdio_invalidate_fileno(pTHX_ FILE *f)
     f->_fileno = -1;
     return 1;
 #  elif defined(__sun__)
-#    if defined(_LP64)
-    /* On solaris, if _LP64 is defined, the FILE structure is this:
-     *
-     *  struct FILE {
-     *      long __pad[16];
-     *  };
-     *
-     * It turns out that the fd is stored in the top 32 bits of
-     * file->__pad[4]. The lower 32 bits contain flags. file->pad[5] appears
-     * to contain a pointer or offset into another structure. All the
-     * remaining fields are zero.
-     *
-     * We set the top bits to -1 (0xFFFFFFFF).
-     */
-    f->__pad[4] |= 0xffffffff00000000L;
-    assert(fileno(f) == 0xffffffff);
-#    else /* !defined(_LP64) */
-    /* _file is just a unsigned char :-(
-       Not clear why we dup() rather than using -1
-       even if that would be treated as 0xFF - so will
-       a dup fail ...
-     */
-    f->_file = PerlLIO_dup(fileno(f));
-#    endif /* defined(_LP64) */
-    return 1;
+    return 0;
 #  elif defined(__hpux)
     f->__fileH = 0xff;
     f->__fileL = 0xff;
@@ -2964,14 +3051,13 @@ PerlIOStdio_invalidate_fileno(pTHX_ FILE *f)
 IV
 PerlIOStdio_close(pTHX_ PerlIO *f)
 {
-    FILE *stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    FILE * const stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
     if (!stdio) {
 	errno = EBADF;
 	return -1;
     }
     else {
         const int fd = fileno(stdio);
-	int socksfd = 0;
 	int invalidate = 0;
 	IV result = 0;
 	int saveerr = 0;
@@ -2983,36 +3069,26 @@ PerlIOStdio_close(pTHX_ PerlIO *f)
 	 */
     	int optval;
     	Sock_size_t optlen = sizeof(int);
-    	if (getsockopt(fd, SOL_SOCKET, SO_TYPE, (void *) &optval, &optlen) == 0) {
-            socksfd = 1;
+	if (getsockopt(fd, SOL_SOCKET, SO_TYPE, (void *) &optval, &optlen) == 0)
 	    invalidate = 1;
-    	}
 #endif
-    	if (PerlIOUnix_refcnt_dec(fd) > 0) {
-	    /* File descriptor still in use */
+	if (PerlIOUnix_refcnt_dec(fd) > 0) /* File descriptor still in use */
 	    invalidate = 1;
-	    socksfd = 0;
-	}
 	if (invalidate) {
-   	    /* For STD* handles don't close the stdio at all
-	       this is because we have shared the FILE * too
-   	     */
-	    if (stdio == stdin) {
-	    	/* Some stdios are buggy fflush-ing inputs */
-	    	return 0;
-	    }
-	    else if (stdio == stdout || stdio == stderr) {
-	    	return PerlIO_flush(f);
-	    }
+	    /* For STD* handles, don't close stdio, since we shared the FILE *, too. */
+	    if (stdio == stdin) /* Some stdios are buggy fflush-ing inputs */
+		return 0;
+	    if (stdio == stdout || stdio == stderr)
+		return PerlIO_flush(f);
             /* Tricky - must fclose(stdio) to free memory but not close(fd)
 	       Use Sarathy's trick from maint-5.6 to invalidate the
 	       fileno slot of the FILE *
 	    */
 	    result = PerlIO_flush(f);
 	    saveerr = errno;
-    	    if (!(invalidate = PerlIOStdio_invalidate_fileno(aTHX_ stdio))) {
-	    	dupfd = PerlLIO_dup(fd);
-	    }
+	    invalidate = PerlIOStdio_invalidate_fileno(aTHX_ stdio);
+	    if (!invalidate)
+		dupfd = PerlLIO_dup(fd);
 	}
         result = PerlSIO_fclose(stdio);
 	/* We treat error from stdio as success if we invalidated
@@ -3022,10 +3098,10 @@ PerlIOStdio_close(pTHX_ PerlIO *f)
 	    errno = saveerr;
 	    result = 0;
 	}
-	if (socksfd) {
-	    /* in SOCKS case let close() determine return value */
-	    result = close(fd);
-	}
+#ifdef SOCKS5_VERSION_NAME
+	/* in SOCKS' case, let close() determine return value */
+	result = close(fd);
+#endif
 	if (dupfd) {
 	    PerlLIO_dup2(dupfd,fd);
 	    PerlLIO_close(dupfd);
@@ -3037,7 +3113,8 @@ PerlIOStdio_close(pTHX_ PerlIO *f)
 SSize_t
 PerlIOStdio_read(pTHX_ PerlIO *f, void *vbuf, Size_t count)
 {
-    FILE *s = PerlIOSelf(f, PerlIOStdio)->stdio;
+    dVAR;
+    FILE * const s = PerlIOSelf(f, PerlIOStdio)->stdio;
     SSize_t got = 0;
     for (;;) {
 	if (count == 1) {
@@ -3068,7 +3145,7 @@ SSize_t
 PerlIOStdio_unread(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 {
     SSize_t unread = 0;
-    FILE *s = PerlIOSelf(f, PerlIOStdio)->stdio;
+    FILE * const s = PerlIOSelf(f, PerlIOStdio)->stdio;
 
 #ifdef STDIO_BUFFER_WRITABLE
     if (PerlIO_fast_gets(f) && PerlIO_has_base(f)) {
@@ -3125,6 +3202,7 @@ PerlIOStdio_unread(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 SSize_t
 PerlIOStdio_write(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 {
+    dVAR;
     SSize_t got;
     for (;;) {
 	got = PerlSIO_fwrite(vbuf, 1, count,
@@ -3140,25 +3218,32 @@ PerlIOStdio_write(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 IV
 PerlIOStdio_seek(pTHX_ PerlIO *f, Off_t offset, int whence)
 {
-    FILE *stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    FILE * const stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    PERL_UNUSED_CONTEXT;
+
     return PerlSIO_fseek(stdio, offset, whence);
 }
 
 Off_t
 PerlIOStdio_tell(pTHX_ PerlIO *f)
 {
-    FILE *stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    FILE * const stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    PERL_UNUSED_CONTEXT;
+
     return PerlSIO_ftell(stdio);
 }
 
 IV
 PerlIOStdio_flush(pTHX_ PerlIO *f)
 {
-    FILE *stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    FILE * const stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    PERL_UNUSED_CONTEXT;
+
     if (PerlIOBase(f)->flags & PERLIO_F_CANWRITE) {
 	return PerlSIO_fflush(stdio);
     }
     else {
+	NOOP;
 #if 0
 	/*
 	 * FIXME: This discards ungetc() and pre-read stuff which is not
@@ -3169,7 +3254,7 @@ PerlIOStdio_flush(pTHX_ PerlIO *f)
 	/*
 	 * Not writeable - sync by attempting a seek
 	 */
-	int err = errno;
+	const int err = errno;
 	if (PerlSIO_fseek(stdio, (Off_t) 0, SEEK_CUR) != 0)
 	    errno = err;
 #endif
@@ -3180,28 +3265,36 @@ PerlIOStdio_flush(pTHX_ PerlIO *f)
 IV
 PerlIOStdio_eof(pTHX_ PerlIO *f)
 {
+    PERL_UNUSED_CONTEXT;
+
     return PerlSIO_feof(PerlIOSelf(f, PerlIOStdio)->stdio);
 }
 
 IV
 PerlIOStdio_error(pTHX_ PerlIO *f)
 {
+    PERL_UNUSED_CONTEXT;
+
     return PerlSIO_ferror(PerlIOSelf(f, PerlIOStdio)->stdio);
 }
 
 void
 PerlIOStdio_clearerr(pTHX_ PerlIO *f)
 {
+    PERL_UNUSED_CONTEXT;
+
     PerlSIO_clearerr(PerlIOSelf(f, PerlIOStdio)->stdio);
 }
 
 void
 PerlIOStdio_setlinebuf(pTHX_ PerlIO *f)
 {
+    PERL_UNUSED_CONTEXT;
+
 #ifdef HAS_SETLINEBUF
     PerlSIO_setlinebuf(PerlIOSelf(f, PerlIOStdio)->stdio);
 #else
-    PerlSIO_setvbuf(PerlIOSelf(f, PerlIOStdio)->stdio, Nullch, _IOLBF, 0);
+    PerlSIO_setvbuf(PerlIOSelf(f, PerlIOStdio)->stdio, NULL, _IOLBF, 0);
 #endif
 }
 
@@ -3209,14 +3302,14 @@ PerlIOStdio_setlinebuf(pTHX_ PerlIO *f)
 STDCHAR *
 PerlIOStdio_get_base(pTHX_ PerlIO *f)
 {
-    FILE *stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    FILE * const stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
     return (STDCHAR*)PerlSIO_get_base(stdio);
 }
 
 Size_t
 PerlIOStdio_get_bufsiz(pTHX_ PerlIO *f)
 {
-    FILE *stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    FILE * const stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
     return PerlSIO_get_bufsiz(stdio);
 }
 #endif
@@ -3225,21 +3318,21 @@ PerlIOStdio_get_bufsiz(pTHX_ PerlIO *f)
 STDCHAR *
 PerlIOStdio_get_ptr(pTHX_ PerlIO *f)
 {
-    FILE *stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    FILE * const stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
     return (STDCHAR*)PerlSIO_get_ptr(stdio);
 }
 
 SSize_t
 PerlIOStdio_get_cnt(pTHX_ PerlIO *f)
 {
-    FILE *stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    FILE * const stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
     return PerlSIO_get_cnt(stdio);
 }
 
 void
 PerlIOStdio_set_ptrcnt(pTHX_ PerlIO *f, STDCHAR * ptr, SSize_t cnt)
 {
-    FILE *stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    FILE * const stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
     if (ptr != NULL) {
 #ifdef STDIO_PTR_LVALUE
 	PerlSIO_set_ptr(stdio, (void*)ptr); /* LHS STDCHAR* cast non-portable */
@@ -3280,8 +3373,10 @@ PerlIOStdio_set_ptrcnt(pTHX_ PerlIO *f, STDCHAR * ptr, SSize_t cnt)
 IV
 PerlIOStdio_fill(pTHX_ PerlIO *f)
 {
-    FILE *stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    FILE * const stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
     int c;
+    PERL_UNUSED_CONTEXT;
+
     /*
      * fflush()ing read-only streams can cause trouble on some stdio-s
      */
@@ -3405,7 +3500,7 @@ PerlIO_exportFILE(PerlIO * f, const char *mode)
 	    PerlIO *f2;
 	    /* De-link any lower layers so new :stdio sticks */
 	    *f = NULL;
-	    if ((f2 = PerlIO_push(aTHX_ f, PERLIO_FUNCS_CAST(&PerlIO_stdio), buf, Nullsv))) {
+	    if ((f2 = PerlIO_push(aTHX_ f, PERLIO_FUNCS_CAST(&PerlIO_stdio), buf, NULL))) {
 		PerlIOStdio *s = PerlIOSelf((f = f2), PerlIOStdio);
 		s->stdio = stdio;
 		/* Link previous lower layers under new one */
@@ -3433,7 +3528,7 @@ PerlIO_findFILE(PerlIO *f)
 	l = *PerlIONext(&l);
     }
     /* Uses fallback "mode" via PerlIO_modestr() in PerlIO_exportFILE */
-    return PerlIO_exportFILE(f, Nullch);
+    return PerlIO_exportFILE(f, NULL);
 }
 
 /* Use this to reverse PerlIO_exportFILE calls. */
@@ -3527,7 +3622,7 @@ PerlIOBuf_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
 #ifdef PERLIO_USING_CRLF
 #  ifdef PERLIO_IS_BINMODE_FD
 		if (PERLIO_IS_BINMODE_FD(fd))
-		    PerlIO_binmode(aTHX_ f,  '<'/*not used*/, O_BINARY, Nullch);
+		    PerlIO_binmode(aTHX_ f,  '<'/*not used*/, O_BINARY, NULL);
 		else
 #  endif
 		/*
@@ -3552,7 +3647,7 @@ PerlIOBuf_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
 IV
 PerlIOBuf_flush(pTHX_ PerlIO *f)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
     int code = 0;
     PerlIO *n = PerlIONext(f);
     if (PerlIOBase(f)->flags & PERLIO_F_WRBUF) {
@@ -3613,7 +3708,7 @@ PerlIOBuf_flush(pTHX_ PerlIO *f)
 IV
 PerlIOBuf_fill(pTHX_ PerlIO *f)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
     PerlIO *n = PerlIONext(f);
     SSize_t avail;
     /*
@@ -3628,6 +3723,8 @@ PerlIOBuf_fill(pTHX_ PerlIO *f)
     if (!b->buf)
 	PerlIO_get_base(f);     /* allocate via vtable */
 
+    assert(b->buf); /* The b->buf does get allocated via the vtable system. */
+
     b->ptr = b->end = b->buf;
 
     if (!PerlIOValid(n)) {
@@ -3654,7 +3751,7 @@ PerlIOBuf_fill(pTHX_ PerlIO *f)
 	}
 	if (avail > 0) {
 	    STDCHAR *ptr = PerlIO_get_ptr(n);
-	    SSize_t cnt = avail;
+	    const SSize_t cnt = avail;
 	    if (avail > (SSize_t)b->bufsiz)
 		avail = b->bufsiz;
 	    Copy(ptr, b->buf, avail, STDCHAR);
@@ -3680,7 +3777,7 @@ SSize_t
 PerlIOBuf_read(pTHX_ PerlIO *f, void *vbuf, Size_t count)
 {
     if (PerlIOValid(f)) {
-        const PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+        const PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
 	if (!b->ptr)
 	    PerlIO_get_base(f);
 	return PerlIOBase_read(aTHX_ f, vbuf, count);
@@ -3692,7 +3789,7 @@ SSize_t
 PerlIOBuf_unread(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 {
     const STDCHAR *buf = (const STDCHAR *) vbuf + count;
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
     SSize_t unread = 0;
     SSize_t avail;
     if (PerlIOBase(f)->flags & PERLIO_F_WRBUF)
@@ -3811,7 +3908,7 @@ PerlIOBuf_seek(pTHX_ PerlIO *f, Off_t offset, int whence)
 Off_t
 PerlIOBuf_tell(pTHX_ PerlIO *f)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
     /*
      * b->posn is file position where b->buf was read, or will be written
      */
@@ -3846,8 +3943,7 @@ PerlIOBuf_popped(pTHX_ PerlIO *f)
     if (b->buf && b->buf != (STDCHAR *) & b->oneword) {
 	Safefree(b->buf);
     }
-    b->buf = NULL;
-    b->ptr = b->end = b->buf;
+    b->ptr = b->end = b->buf = NULL;
     PerlIOBase(f)->flags &= ~(PERLIO_F_RDBUF | PERLIO_F_WRBUF);
     return code;
 }
@@ -3860,8 +3956,7 @@ PerlIOBuf_close(pTHX_ PerlIO *f)
     if (b->buf && b->buf != (STDCHAR *) & b->oneword) {
 	Safefree(b->buf);
     }
-    b->buf = NULL;
-    b->ptr = b->end = b->buf;
+    b->ptr = b->end = b->buf = NULL;
     PerlIOBase(f)->flags &= ~(PERLIO_F_RDBUF | PERLIO_F_WRBUF);
     return code;
 }
@@ -3869,7 +3964,7 @@ PerlIOBuf_close(pTHX_ PerlIO *f)
 STDCHAR *
 PerlIOBuf_get_ptr(pTHX_ PerlIO *f)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    const PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
     if (!b->buf)
 	PerlIO_get_base(f);
     return b->ptr;
@@ -3878,7 +3973,7 @@ PerlIOBuf_get_ptr(pTHX_ PerlIO *f)
 SSize_t
 PerlIOBuf_get_cnt(pTHX_ PerlIO *f)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    const PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
     if (!b->buf)
 	PerlIO_get_base(f);
     if (PerlIOBase(f)->flags & PERLIO_F_RDBUF)
@@ -3889,7 +3984,9 @@ PerlIOBuf_get_cnt(pTHX_ PerlIO *f)
 STDCHAR *
 PerlIOBuf_get_base(pTHX_ PerlIO *f)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
+    PERL_UNUSED_CONTEXT;
+
     if (!b->buf) {
 	if (!b->bufsiz)
 	    b->bufsiz = 4096;
@@ -3898,8 +3995,7 @@ PerlIOBuf_get_base(pTHX_ PerlIO *f)
 	    b->buf = (STDCHAR *) & b->oneword;
 	    b->bufsiz = sizeof(b->oneword);
 	}
-	b->ptr = b->buf;
-	b->end = b->ptr;
+	b->end = b->ptr = b->buf;
     }
     return b->buf;
 }
@@ -3907,7 +4003,7 @@ PerlIOBuf_get_base(pTHX_ PerlIO *f)
 Size_t
 PerlIOBuf_bufsiz(pTHX_ PerlIO *f)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    const PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
     if (!b->buf)
 	PerlIO_get_base(f);
     return (b->end - b->buf);
@@ -3916,7 +4012,7 @@ PerlIOBuf_bufsiz(pTHX_ PerlIO *f)
 void
 PerlIOBuf_set_ptrcnt(pTHX_ PerlIO *f, STDCHAR * ptr, SSize_t cnt)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
     if (!b->buf)
 	PerlIO_get_base(f);
     b->ptr = ptr;
@@ -4005,7 +4101,7 @@ PerlIOPending_seek(pTHX_ PerlIO *f, Off_t offset, int whence)
 IV
 PerlIOPending_flush(pTHX_ PerlIO *f)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
     if (b->buf && b->buf != (STDCHAR *) & b->oneword) {
 	Safefree(b->buf);
 	b->buf = NULL;
@@ -4029,7 +4125,7 @@ IV
 PerlIOPending_pushed(pTHX_ PerlIO *f, const char *mode, SV *arg, PerlIO_funcs *tab)
 {
     const IV code = PerlIOBase_pushed(aTHX_ f, mode, arg, tab);
-    PerlIOl *l = PerlIOBase(f);
+    PerlIOl * const l = PerlIOBase(f);
     /*
      * Our PerlIO_fast_gets must match what we are pushed on, or sv_gets()
      * etc. get muddled when it changes mid-string when we auto-pop.
@@ -4147,7 +4243,7 @@ PerlIOCrlf_pushed(pTHX_ PerlIO *f, const char *mode, SV *arg, PerlIO_funcs *tab)
 SSize_t
 PerlIOCrlf_unread(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 {
-    PerlIOCrlf *c = PerlIOSelf(f, PerlIOCrlf);
+    PerlIOCrlf * const c = PerlIOSelf(f, PerlIOCrlf);
     if (c->nl) {	/* XXXX Shouldn't it be done only if b->ptr > c->nl? */
 	*(c->nl) = 0xd;
 	c->nl = NULL;
@@ -4169,7 +4265,7 @@ PerlIOCrlf_unread(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 		b->posn -= b->bufsiz;
 	    }
 	    while (count > 0 && b->ptr > b->buf) {
-		int ch = *--buf;
+		const int ch = *--buf;
 		if (ch == '\n') {
 		    if (b->ptr - 2 >= b->buf) {
 			*--(b->ptr) = 0xa;
@@ -4199,11 +4295,11 @@ PerlIOCrlf_unread(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 SSize_t
 PerlIOCrlf_get_cnt(pTHX_ PerlIO *f)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
     if (!b->buf)
 	PerlIO_get_base(f);
     if (PerlIOBase(f)->flags & PERLIO_F_RDBUF) {
-	PerlIOCrlf *c = PerlIOSelf(f, PerlIOCrlf);
+	PerlIOCrlf * const c = PerlIOSelf(f, PerlIOCrlf);
 	if ((PerlIOBase(f)->flags & PERLIO_F_CRLF) && (!c->nl || *c->nl == 0xd)) {
 	    STDCHAR *nl = (c->nl) ? c->nl : b->ptr;
 	  scan:
@@ -4271,8 +4367,8 @@ PerlIOCrlf_get_cnt(pTHX_ PerlIO *f)
 void
 PerlIOCrlf_set_ptrcnt(pTHX_ PerlIO *f, STDCHAR * ptr, SSize_t cnt)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
-    PerlIOCrlf *c = PerlIOSelf(f, PerlIOCrlf);
+    PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
+    PerlIOCrlf * const c = PerlIOSelf(f, PerlIOCrlf);
     if (!b->buf)
 	PerlIO_get_base(f);
     if (!ptr) {
@@ -4289,6 +4385,7 @@ PerlIOCrlf_set_ptrcnt(pTHX_ PerlIO *f, STDCHAR * ptr, SSize_t cnt)
 	ptr -= cnt;
     }
     else {
+	NOOP;
 #if 0
 	/*
 	 * Test code - delete when it works ...
@@ -4328,15 +4425,15 @@ PerlIOCrlf_write(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
     if (!(PerlIOBase(f)->flags & PERLIO_F_CRLF))
 	return PerlIOBuf_write(aTHX_ f, vbuf, count);
     else {
-	PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+	PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
 	const STDCHAR *buf = (const STDCHAR *) vbuf;
-	const STDCHAR *ebuf = buf + count;
+	const STDCHAR * const ebuf = buf + count;
 	if (!b->buf)
 	    PerlIO_get_base(f);
 	if (!(PerlIOBase(f)->flags & PERLIO_F_CANWRITE))
 	    return 0;
 	while (buf < ebuf) {
-	    STDCHAR *eptr = b->buf + b->bufsiz;
+	    const STDCHAR * const eptr = b->buf + b->bufsiz;
 	    PerlIOBase(f)->flags |= PERLIO_F_WRBUF;
 	    while (buf < ebuf && b->ptr < eptr) {
 		if (*buf == '\n') {
@@ -4358,8 +4455,7 @@ PerlIOCrlf_write(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 		    }
 		}
 		else {
-		    int ch = *buf++;
-		    *(b->ptr)++ = ch;
+		    *(b->ptr)++ = *buf++;
 		}
 		if (b->ptr >= eptr) {
 		    PerlIO_flush(f);
@@ -4376,7 +4472,7 @@ PerlIOCrlf_write(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 IV
 PerlIOCrlf_flush(pTHX_ PerlIO *f)
 {
-    PerlIOCrlf *c = PerlIOSelf(f, PerlIOCrlf);
+    PerlIOCrlf * const c = PerlIOSelf(f, PerlIOCrlf);
     if (c->nl) {
 	*(c->nl) = 0xd;
 	c->nl = NULL;
@@ -4454,7 +4550,7 @@ PerlIOMmap_map(pTHX_ PerlIO *f)
     if (m->len)
 	abort();
     if (flags & PERLIO_F_CANREAD) {
-	PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+	PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
 	const int fd = PerlIO_fileno(f);
 	Stat_t st;
 	code = Fstat(fd, &st);
@@ -4508,10 +4604,10 @@ PerlIOMmap_map(pTHX_ PerlIO *f)
 IV
 PerlIOMmap_unmap(pTHX_ PerlIO *f)
 {
-    PerlIOMmap *m = PerlIOSelf(f, PerlIOMmap);
-    PerlIOBuf *b = &m->base;
+    PerlIOMmap * const m = PerlIOSelf(f, PerlIOMmap);
     IV code = 0;
     if (m->len) {
+	PerlIOBuf * const b = &m->base;
 	if (b->buf) {
 	    code = munmap(m->mptr, m->len);
 	    b->buf = NULL;
@@ -4529,8 +4625,8 @@ PerlIOMmap_unmap(pTHX_ PerlIO *f)
 STDCHAR *
 PerlIOMmap_get_base(pTHX_ PerlIO *f)
 {
-    PerlIOMmap *m = PerlIOSelf(f, PerlIOMmap);
-    PerlIOBuf *b = &m->base;
+    PerlIOMmap * const m = PerlIOSelf(f, PerlIOMmap);
+    PerlIOBuf * const b = &m->base;
     if (b->buf && (PerlIOBase(f)->flags & PERLIO_F_RDBUF)) {
 	/*
 	 * Already have a readbuffer in progress
@@ -4562,8 +4658,8 @@ PerlIOMmap_get_base(pTHX_ PerlIO *f)
 SSize_t
 PerlIOMmap_unread(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 {
-    PerlIOMmap *m = PerlIOSelf(f, PerlIOMmap);
-    PerlIOBuf *b = &m->base;
+    PerlIOMmap * const m = PerlIOSelf(f, PerlIOMmap);
+    PerlIOBuf * const b = &m->base;
     if (PerlIOBase(f)->flags & PERLIO_F_WRBUF)
 	PerlIO_flush(f);
     if (b->ptr && (b->ptr - count) >= b->buf
@@ -4620,8 +4716,8 @@ PerlIOMmap_write(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 IV
 PerlIOMmap_flush(pTHX_ PerlIO *f)
 {
-    PerlIOMmap *m = PerlIOSelf(f, PerlIOMmap);
-    PerlIOBuf *b = &m->base;
+    PerlIOMmap * const m = PerlIOSelf(f, PerlIOMmap);
+    PerlIOBuf * const b = &m->base;
     IV code = PerlIOBuf_flush(aTHX_ f);
     /*
      * Now we are "synced" at PerlIOBuf level
@@ -4648,7 +4744,7 @@ PerlIOMmap_flush(pTHX_ PerlIO *f)
 IV
 PerlIOMmap_fill(pTHX_ PerlIO *f)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
     IV code = PerlIO_flush(f);
     if (code == 0 && !b->buf) {
 	code = PerlIOMmap_map(aTHX_ f);
@@ -4662,8 +4758,8 @@ PerlIOMmap_fill(pTHX_ PerlIO *f)
 IV
 PerlIOMmap_close(pTHX_ PerlIO *f)
 {
-    PerlIOMmap *m = PerlIOSelf(f, PerlIOMmap);
-    PerlIOBuf *b = &m->base;
+    PerlIOMmap * const m = PerlIOSelf(f, PerlIOMmap);
+    PerlIOBuf * const b = &m->base;
     IV code = PerlIO_flush(f);
     if (m->bbuf) {
 	b->buf = m->bbuf;
@@ -4718,6 +4814,7 @@ PERLIO_FUNCS_DECL(PerlIO_mmap) = {
 PerlIO *
 Perl_PerlIO_stdin(pTHX)
 {
+    dVAR;
     if (!PL_perlio) {
 	PerlIO_stdstreams(aTHX);
     }
@@ -4727,6 +4824,7 @@ Perl_PerlIO_stdin(pTHX)
 PerlIO *
 Perl_PerlIO_stdout(pTHX)
 {
+    dVAR;
     if (!PL_perlio) {
 	PerlIO_stdstreams(aTHX);
     }
@@ -4736,6 +4834,7 @@ Perl_PerlIO_stdout(pTHX)
 PerlIO *
 Perl_PerlIO_stderr(pTHX)
 {
+    dVAR;
     if (!PL_perlio) {
 	PerlIO_stdstreams(aTHX);
     }
@@ -4765,7 +4864,7 @@ PerlIO_getname(PerlIO *f, char *buf)
     PERL_UNUSED_ARG(f);
     PERL_UNUSED_ARG(buf);
     Perl_croak(aTHX_ "Don't know how to get file name");
-    return Nullch;
+    return NULL;
 #endif
 }
 
@@ -4781,7 +4880,7 @@ PerlIO *
 PerlIO_fdopen(int fd, const char *mode)
 {
     dTHX;
-    return PerlIO_openn(aTHX_ Nullch, mode, fd, 0, 0, NULL, 0, NULL);
+    return PerlIO_openn(aTHX_ NULL, mode, fd, 0, 0, NULL, 0, NULL);
 }
 
 #undef PerlIO_open
@@ -4789,8 +4888,8 @@ PerlIO *
 PerlIO_open(const char *path, const char *mode)
 {
     dTHX;
-    SV *name = sv_2mortal(newSVpvn(path, strlen(path)));
-    return PerlIO_openn(aTHX_ Nullch, mode, -1, 0, 0, NULL, 1, &name);
+    SV *name = sv_2mortal(newSVpv(path, 0));
+    return PerlIO_openn(aTHX_ NULL, mode, -1, 0, 0, NULL, 1, &name);
 }
 
 #undef Perlio_reopen
@@ -4798,8 +4897,8 @@ PerlIO *
 PerlIO_reopen(const char *path, const char *mode, PerlIO *f)
 {
     dTHX;
-    SV *name = sv_2mortal(newSVpvn(path, strlen(path)));
-    return PerlIO_openn(aTHX_ Nullch, mode, -1, 0, 0, f, 1, &name);
+    SV *name = sv_2mortal(newSVpv(path,0));
+    return PerlIO_openn(aTHX_ NULL, mode, -1, 0, 0, f, 1, &name);
 }
 
 #undef PerlIO_getc
@@ -4841,8 +4940,7 @@ int
 PerlIO_puts(PerlIO *f, const char *s)
 {
     dTHX;
-    STRLEN len = strlen(s);
-    return PerlIO_write(f, s, len);
+    return PerlIO_write(f, s, strlen(s));
 }
 
 #undef PerlIO_rewind
@@ -4859,7 +4957,7 @@ int
 PerlIO_vprintf(PerlIO *f, const char *fmt, va_list ap)
 {
     dTHX;
-    SV *sv = newSVpvn("", 0);
+    SV * const sv = newSVpvs("");
     const char *s;
     STRLEN len;
     SSize_t wrote;
@@ -4913,7 +5011,7 @@ PerlIO_tmpfile(void)
 	  f = PerlIO_fdopen(fd, "w+b");
 #else /* WIN32 */
 #    if defined(HAS_MKSTEMP) && ! defined(VMS) && ! defined(OS2)
-     SV *sv = newSVpv("/tmp/PerlIO_XXXXXX", 0);
+     SV * const sv = newSVpvs("/tmp/PerlIO_XXXXXX");
      /*
       * I have no idea how portable mkstemp() is ... NI-S
       */
@@ -4926,13 +5024,13 @@ PerlIO_tmpfile(void)
 	  SvREFCNT_dec(sv);
      }
 #    else	/* !HAS_MKSTEMP, fallback to stdio tmpfile(). */
-     FILE *stdio = PerlSIO_tmpfile();
+     FILE * const stdio = PerlSIO_tmpfile();
 
      if (stdio) {
 	  if ((f = PerlIO_push(aTHX_(PerlIO_allocate(aTHX)),
                                PERLIO_FUNCS_CAST(&PerlIO_stdio),
-			       "w+", Nullsv))) {
-               PerlIOStdio *s = PerlIOSelf(f, PerlIOStdio);
+			       "w+", NULL))) {
+	       PerlIOStdio * const s = PerlIOSelf(f, PerlIOStdio);
 
                if (s)
                     s->stdio = stdio;
@@ -4963,7 +5061,7 @@ PerlIO_setpos(PerlIO *f, SV *pos)
     dTHX;
     if (SvOK(pos)) {
 	STRLEN len;
-	Off_t *posn = (Off_t *) SvPV(pos, len);
+	const Off_t * const posn = (Off_t *) SvPV(pos, len);
 	if (f && len == sizeof(Off_t))
 	    return PerlIO_seek(f, *posn, SEEK_SET);
     }
@@ -4978,7 +5076,7 @@ PerlIO_setpos(PerlIO *f, SV *pos)
     dTHX;
     if (SvOK(pos)) {
 	STRLEN len;
-	Fpos_t *fpos = (Fpos_t *) SvPV(pos, len);
+	Fpos_t * const fpos = (Fpos_t *) SvPV(pos, len);
 	if (f && len == sizeof(Fpos_t)) {
 #if defined(USE_64_BIT_STDIO) && defined(USE_FSETPOS64)
 	    return fsetpos64(f, fpos);
@@ -5044,8 +5142,8 @@ vfprintf(FILE *fd, char *pat, char *args)
 int
 PerlIO_vsprintf(char *s, int n, const char *fmt, va_list ap)
 {
-    dVAR;
-    const int val = vsprintf(s, fmt, ap);
+    dTHX;
+    const int val = my_vsnprintf(s, n > 0 ? n : 0, fmt, ap);
     if (n >= 0) {
 	if (strlen(s) >= (STRLEN) n) {
 	    dTHX;