X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=perlio.c;h=75a9ef5328e2a095ca0aa378801063e945ca371e;hb=3edf23ff129b6c5edde184cb3b63953432223591;hp=05963d0ff08606458221f539f83f3178333c44a5;hpb=b464bac0b70c4876af1296864220315edde8461d;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/perlio.c b/perlio.c
index 05963d0..75a9ef5 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.
  */
@@ -66,7 +66,7 @@ int mkstemp(char*);
 /* Call the callback or PerlIOBase, and return failure. */
 #define Perl_PerlIO_or_Base(f, callback, base, failure, args) 	\
 	if (PerlIOValid(f)) {					\
-		const PerlIO_funcs *tab = PerlIOBase(f)->tab;	\
+		const PerlIO_funcs * const tab = PerlIOBase(f)->tab;\
 		if (tab && tab->callback)			\
 			return (*tab->callback) args;		\
 		else						\
@@ -79,7 +79,7 @@ int mkstemp(char*);
 /* Call the callback or fail, and return failure. */
 #define Perl_PerlIO_or_fail(f, callback, failure, args) 	\
 	if (PerlIOValid(f)) {					\
-		const PerlIO_funcs *tab = PerlIOBase(f)->tab;	\
+		const PerlIO_funcs * const tab = PerlIOBase(f)->tab;\
 		if (tab && tab->callback)			\
 			return (*tab->callback) args;		\
 		SETERRNO(EINVAL, LIB_INVARG);			\
@@ -91,7 +91,7 @@ int mkstemp(char*);
 /* Call the callback or PerlIOBase, and be void. */
 #define Perl_PerlIO_or_Base_void(f, callback, base, args) 	\
 	if (PerlIOValid(f)) {					\
-		const PerlIO_funcs *tab = PerlIOBase(f)->tab;	\
+		const PerlIO_funcs * const tab = PerlIOBase(f)->tab;\
 		if (tab && tab->callback)			\
 			(*tab->callback) args;			\
 		else						\
@@ -103,7 +103,7 @@ int mkstemp(char*);
 /* Call the callback or fail, and be void. */
 #define Perl_PerlIO_or_fail_void(f, callback, args) 		\
 	if (PerlIOValid(f)) {					\
-		const PerlIO_funcs *tab = PerlIOBase(f)->tab;	\
+		const PerlIO_funcs * const tab = PerlIOBase(f)->tab;\
 		if (tab && tab->callback)			\
 			(*tab->callback) args;			\
 		else						\
@@ -122,11 +122,11 @@ 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
@@ -137,35 +137,38 @@ 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
-    (void)fp;
-    (void)iotype;
-    (void)mode;
+    PERL_UNUSED_ARG(fp);
+    PERL_UNUSED_ARG(iotype);
+    PERL_UNUSED_ARG(mode);
     return 1;
 #  endif
 #endif
@@ -248,9 +251,9 @@ int
 PerlIO_binmode(pTHX_ PerlIO *fp, int iotype, int mode, const char *names)
 {
 #ifdef USE_SFIO
-    (void)iotype;
-    (void)mode;
-    (void)names;
+    PERL_UNUSED_ARG(iotype);
+    PERL_UNUSED_ARG(mode);
+    PERL_UNUSED_ARG(names);
     return 1;
 #else
     return perlsio_binmode(fp, iotype, mode);
@@ -260,7 +263,7 @@ 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 +276,10 @@ 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 */
@@ -308,7 +312,7 @@ PerlIO_openn(pTHX_ const char *layers, const char *mode, int fd,
 	if (*args == &PL_sv_undef)
 	    return PerlIO_tmpfile();
 	else {
-	    const char *name = SvPV_nolen(*args);
+	    const char *name = SvPV_nolen_const(*args);
 	    if (*mode == IoTYPE_NUMERIC) {
 		fd = PerlLIO_open3(name, imode, perm);
 		if (fd >= 0)
@@ -334,7 +338,7 @@ XS(XS_PerlIO__Layer__find)
     if (items < 2)
 	Perl_croak(aTHX_ "Usage class->find(name[,load])");
     else {
-	const char *name = SvPV_nolen(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);
@@ -458,7 +462,7 @@ 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
@@ -466,25 +470,22 @@ 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 = vsprintf(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);
 
-	s = SvPV(sv, len);
+	s = SvPV_const(sv, len);
 	PerlLIO_write(PL_perlio_debug_fd, s, len);
 	SvREFCNT_dec(sv);
 #endif
@@ -521,7 +522,7 @@ PerlIO_allocate(pTHX)
 	    }
 	}
     }
-    Newz('I',f,PERLIO_TABLE_SIZE,PerlIO);
+    Newxz(f,PERLIO_TABLE_SIZE,PerlIO);
     if (!f) {
 	return NULL;
     }
@@ -551,12 +552,12 @@ 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);
 	    }
@@ -571,7 +572,7 @@ PerlIO_list_t *
 PerlIO_list_alloc(pTHX)
 {
     PerlIO_list_t *list;
-    Newz('L', list, 1, PerlIO_list_t);
+    Newxz(list, 1, PerlIO_list_t);
     list->refcnt = 1;
     return list;
 }
@@ -603,7 +604,7 @@ PerlIO_list_push(pTHX_ PerlIO_list_t *list, PerlIO_funcs *funcs, SV *arg)
 	if (list->array)
 	    Renew(list->array, list->len, PerlIO_pair_t);
 	else
-	    New('l', list->array, list->len, PerlIO_pair_t);
+	    Newx(list->array, list->len, PerlIO_pair_t);
     }
     p = &(list->array[list->cur++]);
     p->funcs = funcs;
@@ -650,6 +651,9 @@ PerlIO_clone(pTHX_ PerlInterpreter *proto, CLONE_PARAMS *param)
 		f++;
 	    }
 	}
+#else
+    PERL_UNUSED_ARG(proto);
+    PERL_UNUSED_ARG(param);
 #endif
 }
 
@@ -666,7 +670,7 @@ PerlIO_destruct(pTHX)
 	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);
@@ -685,7 +689,7 @@ 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) {
@@ -711,24 +715,24 @@ PerlIO_pop(pTHX_ PerlIO *f)
 AV *
 PerlIO_get_layers(pTHX_ PerlIO *f)
 {
-     AV *av = newAV();
+    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;
 }
 
 /*--------------------------------------------------------------------------------------*/
@@ -744,7 +748,7 @@ PerlIO_find_layer(pTHX_ const char *name, STRLEN len, int load)
     if ((SSize_t) len <= 0)
 	len = strlen(name);
     for (i = 0; i < PL_known_layers->cur; i++) {
-	PerlIO_funcs *f = PL_known_layers->array[i].funcs;
+	PerlIO_funcs * const f = PL_known_layers->array[i].funcs;
 	if (memEQ(f->name, name, len) && f->name[len] == 0) {
 	    PerlIO_debug("%.*s => %p\n", (int) len, name, (void*)f);
 	    return f;
@@ -756,10 +760,10 @@ 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 *pkgsv = newSVpvn("PerlIO", 6);
-	    SV *layer = newSVpvn(name, len);
-	    CV *cv  = get_cv("PerlIO::Layer::NoWarnings", FALSE);
-    	    ENTER;
+	    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);
@@ -786,9 +790,9 @@ 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;
@@ -798,9 +802,9 @@ 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;
@@ -831,8 +835,8 @@ 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;
@@ -844,8 +848,8 @@ XS(XS_io_MODIFY_SCALAR_ATTRIBUTES)
     Perl_warn(aTHX_ "attrib %" SVf, sv);
     for (i = 2; i < items; i++) {
 	STRLEN len;
-	const char *name = SvPV(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));
 	}
@@ -863,8 +867,8 @@ XS(XS_io_MODIFY_SCALAR_ATTRIBUTES)
 SV *
 PerlIO_tab_sv(pTHX_ PerlIO_funcs *tab)
 {
-    HV *stash = gv_stashpv("PerlIO::Layer", TRUE);
-    SV *sv = sv_bless(newRV_noinc(newSViv(PTR2IV(tab))), stash);
+    HV * const stash = gv_stashpvs("PerlIO::Layer", TRUE);
+    SV * const sv = sv_bless(newRV_noinc(newSViv(PTR2IV(tab))), stash);
     return sv;
 }
 
@@ -875,7 +879,7 @@ XS(XS_PerlIO__Layer__NoWarnings)
      */
     dXSARGS;
     if (items)
-    	PerlIO_debug("warning:%s\n",SvPV_nolen(ST(0)));
+    	PerlIO_debug("warning:%s\n",SvPV_nolen_const(ST(0)));
     XSRETURN(0);
 }
 
@@ -886,9 +890,9 @@ XS(XS_PerlIO__Layer__find)
 	Perl_croak(aTHX_ "Usage class->find(name[,load])");
     else {
 	STRLEN len;
-	const char *name = SvPV(ST(1), len);
+	const char * const name = SvPV_const(ST(1), len);
 	const bool load = (items > 2) ? SvTRUE(ST(2)) : 0;
-	PerlIO_funcs *layer = PerlIO_find_layer(aTHX_ name, len, load);
+	PerlIO_funcs * const layer = PerlIO_find_layer(aTHX_ name, len, load);
 	ST(0) =
 	    (layer) ? sv_2mortal(PerlIO_tab_sv(aTHX_ layer)) :
 	    &PL_sv_undef;
@@ -976,8 +980,7 @@ PerlIO_parse_layers(pTHX_ PerlIO_list_t *av, const char *names)
 		    }
 		}
 		if (e > s) {
-		    const bool warn_layer = ckWARN(WARN_LAYER);
-		    PerlIO_funcs *layer =
+		    PerlIO_funcs * const layer =
 			PerlIO_find_layer(aTHX_ s, llen, 1);
 		    if (layer) {
 			PerlIO_list_push(aTHX_ av, layer,
@@ -986,7 +989,7 @@ PerlIO_parse_layers(pTHX_ PerlIO_list_t *av, const char *names)
 					 &PL_sv_undef);
 		    }
 		    else {
-			if (warn_layer)
+			if (ckWARN(WARN_LAYER))
 			    Perl_warner(aTHX_ packWARN(WARN_LAYER), "Unknown PerlIO layer \"%.*s\"",
 				  (int) llen, s);
 			return -1;
@@ -1036,9 +1039,9 @@ PerlIO_layer_fetch(pTHX_ PerlIO_list_t *av, IV n, PerlIO_funcs *def)
 IV
 PerlIOPop_pushed(pTHX_ PerlIO *f, const char *mode, SV *arg, PerlIO_funcs *tab)
 {
-    (void)mode;
-    (void)arg;
-    (void)tab;
+    PERL_UNUSED_ARG(mode);
+    PERL_UNUSED_ARG(arg);
+    PERL_UNUSED_ARG(tab);
     if (PerlIOValid(f)) {
 	PerlIO_flush(f);
 	PerlIO_pop(aTHX_ f);
@@ -1082,7 +1085,7 @@ PerlIO_list_t *
 PerlIO_default_layers(pTHX)
 {
     if (!PL_def_layerlist) {
-	const char *s = (PL_tainting) ? Nullch : PerlEnv_getenv("PERLIO");
+	const char * const s = (PL_tainting) ? Nullch : 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));
@@ -1132,7 +1135,7 @@ Perl_boot_core_PerlIO(pTHX)
 PerlIO_funcs *
 PerlIO_default_layer(pTHX_ I32 n)
 {
-    PerlIO_list_t *av = PerlIO_default_layers(aTHX);
+    PerlIO_list_t * const av = PerlIO_default_layers(aTHX);
     if (n < 0)
 	n += av->cur;
     return PerlIO_layer_fetch(aTHX_ av, n, PERLIO_FUNCS_CAST(&PerlIO_stdio));
@@ -1165,7 +1168,7 @@ PerlIO_push(pTHX_ PerlIO *f, PERLIO_FUNCS_DECL(*tab), const char *mode, SV *arg)
 	    goto mismatch;
 	}
 	/* Real layer with a data area */
-	Newc('L',l,tab->size,char,PerlIOl);
+	Newxc(l,tab->size,char,PerlIOl);
 	if (l && f) {
 	    Zero(l, tab->size, char);
 	    l->next = *f;
@@ -1213,9 +1216,9 @@ PerlIOBase_binmode(pTHX_ PerlIO *f)
 IV
 PerlIORaw_pushed(pTHX_ PerlIO *f, const char *mode, SV *arg, PerlIO_funcs *tab)
 {
-    (void)mode;
-    (void)arg;
-    (void)tab;
+    PERL_UNUSED_ARG(mode);
+    PERL_UNUSED_ARG(arg);
+    PERL_UNUSED_ARG(tab);
 
     if (PerlIOValid(f)) {
 	PerlIO *t;
@@ -1257,7 +1260,7 @@ PerlIO_apply_layera(pTHX_ PerlIO *f, const char *mode,
 {
     int code = 0;
     while (n < max) {
-	PerlIO_funcs *tab = PerlIO_layer_fetch(aTHX_ layers, n, NULL);
+	PerlIO_funcs * const tab = PerlIO_layer_fetch(aTHX_ layers, n, NULL);
 	if (tab) {
 	    if (!PerlIO_push(aTHX_ f, tab, mode, PerlIOArg)) {
 		code = -1;
@@ -1274,7 +1277,7 @@ PerlIO_apply_layers(pTHX_ PerlIO *f, const char *mode, const char *names)
 {
     int code = 0;
     if (f && names) {
-	PerlIO_list_t *layers = PerlIO_list_alloc(aTHX);
+	PerlIO_list_t * const layers = PerlIO_list_alloc(aTHX);
 	code = PerlIO_parse_layers(aTHX_ layers, names);
 	if (code == 0) {
 	    code = PerlIO_apply_layera(aTHX_ f, mode, layers, 0, layers->cur);
@@ -1293,9 +1296,10 @@ 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
@@ -1349,7 +1353,7 @@ int
 PerlIO__close(pTHX_ PerlIO *f)
 {
     if (PerlIOValid(f)) {
-	PerlIO_funcs *tab = PerlIOBase(f)->tab;
+	PerlIO_funcs * const tab = PerlIOBase(f)->tab;
 	if (tab && tab->Close)
 	    return (*tab->Close)(aTHX_ f);
 	else
@@ -1385,15 +1389,15 @@ PerlIO_context_layers(pTHX_ const char *mode)
      * 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(layers, len);
+	    type = SvPV_const(layers, len);
 	    if (type && mode[0] != 'r') {
 		/*
 		 * 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;
 		}
@@ -1410,20 +1414,20 @@ PerlIO_layer_from_ref(pTHX_ SV *sv)
      * 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;
 }
@@ -1437,13 +1441,13 @@ PerlIO_resolve_layers(pTHX_ const char *layers,
     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
 	 */
 	if (SvROK(arg) && !sv_isobject(arg)) {
-	    PerlIO_funcs *handler = PerlIO_layer_from_ref(aTHX_ SvRV(arg));
+	    PerlIO_funcs * const handler = PerlIO_layer_from_ref(aTHX_ SvRV(arg));
 	    if (handler) {
 		def = PerlIO_list_alloc(aTHX);
 		PerlIO_list_push(aTHX_ def, handler, &PL_sv_undef);
@@ -1456,7 +1460,7 @@ 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;
@@ -1492,7 +1496,7 @@ PerlIO_openn(pTHX_ const char *layers, const char *mode, int fd,
 {
     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);
@@ -1510,7 +1514,7 @@ PerlIO_openn(pTHX_ const char *layers, const char *mode, int fd,
 	    PerlIOl *l = *f;
 	    layera = PerlIO_list_alloc(aTHX);
 	    while (l) {
-		SV *arg = (l->tab->Getarg)
+		SV * const arg = (l->tab->Getarg)
 			? (*l->tab->Getarg) (aTHX_ &l, NULL, 0)
 			: &PL_sv_undef;
 		PerlIO_list_push(aTHX_ layera, l->tab, arg);
@@ -1528,7 +1532,7 @@ PerlIO_openn(pTHX_ const char *layers, const char *mode, int fd,
 	 */
 	n = layera->cur - 1;
 	while (n >= 0) {
-	    PerlIO_funcs *t = PerlIO_layer_fetch(aTHX_ layera, n, NULL);
+	    PerlIO_funcs * const t = PerlIO_layer_fetch(aTHX_ layera, n, NULL);
 	    if (t && t->Open) {
 		tab = t;
 		break;
@@ -1543,8 +1547,8 @@ 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);
@@ -1707,7 +1711,7 @@ int
 PerlIO_has_base(PerlIO *f)
 {
      if (PerlIOValid(f)) {
-          const PerlIO_funcs *tab = PerlIOBase(f)->tab;
+	  const PerlIO_funcs * const tab = PerlIOBase(f)->tab;
 
 	  if (tab)
 	       return (tab->Get_base != NULL);
@@ -1723,7 +1727,7 @@ int
 PerlIO_fast_gets(PerlIO *f)
 {
     if (PerlIOValid(f) && (PerlIOBase(f)->flags & PERLIO_F_FASTGETS)) {
-	 const PerlIO_funcs *tab = PerlIOBase(f)->tab;
+	 const PerlIO_funcs * const tab = PerlIOBase(f)->tab;
 
 	 if (tab)
 	      return (tab->Set_ptrcnt != NULL);
@@ -1739,7 +1743,7 @@ int
 PerlIO_has_cntptr(PerlIO *f)
 {
     if (PerlIOValid(f)) {
-	const PerlIO_funcs *tab = PerlIOBase(f)->tab;
+	const PerlIO_funcs * const tab = PerlIOBase(f)->tab;
 
 	if (tab)
 	     return (tab->Get_ptr != NULL && tab->Get_cnt != NULL);
@@ -1755,7 +1759,7 @@ int
 PerlIO_canset_cnt(PerlIO *f)
 {
     if (PerlIOValid(f)) {
-	  const PerlIO_funcs *tab = PerlIOBase(f)->tab;
+	  const PerlIO_funcs * const tab = PerlIOBase(f)->tab;
 
 	  if (tab)
 	       return (tab->Set_ptrcnt != NULL);
@@ -1812,8 +1816,8 @@ 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)
 {
-    (void)mode;
-    (void)arg;
+    PERL_UNUSED_ARG(mode);
+    PERL_UNUSED_ARG(arg);
     if (PerlIOValid(f)) {
 	if (tab->kind & PERLIO_K_UTF8)
 	    PerlIOBase(f)->flags |= PERLIO_F_UTF8;
@@ -1891,8 +1895,8 @@ PerlIORaw_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
 	       IV n, const char *mode, int fd, int imode, int perm,
 	       PerlIO *old, int narg, SV **args)
 {
-    PerlIO_funcs *tab = PerlIO_default_btm();
-    (void)self;
+    PerlIO_funcs * const tab = PerlIO_default_btm();
+    PERL_UNUSED_ARG(self);
     if (tab && tab->Open)
 	 return (*tab->Open) (aTHX_ tab, layers, n - 1, mode, fd, imode, perm,
 			      old, narg, args);
@@ -1979,7 +1983,7 @@ IV
 PerlIOBase_pushed(pTHX_ PerlIO *f, const char *mode, SV *arg, PerlIO_funcs *tab)
 {
     PerlIOl * const l = PerlIOBase(f);
-    (void)arg;
+    PERL_UNUSED_ARG(arg);
 
     l->flags &= ~(PERLIO_F_CANREAD | PERLIO_F_CANWRITE |
 		  PERLIO_F_TRUNCATE | PERLIO_F_APPEND);
@@ -2037,7 +2041,7 @@ PerlIOBase_pushed(pTHX_ PerlIO *f, const char *mode, SV *arg, PerlIO_funcs *tab)
 IV
 PerlIOBase_popped(pTHX_ PerlIO *f)
 {
-    (void)f;
+    PERL_UNUSED_ARG(f);
     return 0;
 }
 
@@ -2064,6 +2068,8 @@ PerlIOBase_read(pTHX_ PerlIO *f, void *vbuf, Size_t count)
 	    return 0;
 	}
 	while (count > 0) {
+	 get_cnt:
+	  {
 	    SSize_t avail = PerlIO_get_cnt(f);
 	    SSize_t take = 0;
 	    if (avail > 0)
@@ -2074,11 +2080,14 @@ PerlIOBase_read(pTHX_ PerlIO *f, void *vbuf, Size_t count)
 		PerlIO_set_ptrcnt(f, ptr + take, (avail -= take));
 		count -= take;
 		buf += take;
+		if (avail == 0)		/* set_ptrcnt could have reset avail */
+		    goto get_cnt;
 	    }
 	    if (count > 0 && avail <= 0) {
 		if (PerlIO_fill(f) != 0)
 		    break;
 	    }
+	  }
 	}
 	return (buf - (STDCHAR *) vbuf);
     }
@@ -2088,14 +2097,14 @@ PerlIOBase_read(pTHX_ PerlIO *f, void *vbuf, Size_t count)
 IV
 PerlIOBase_noop_ok(pTHX_ PerlIO *f)
 {
-    (void)f;
+    PERL_UNUSED_ARG(f);
     return 0;
 }
 
 IV
 PerlIOBase_noop_fail(pTHX_ PerlIO *f)
 {
-    (void)f;
+    PERL_UNUSED_ARG(f);
     return -1;
 }
 
@@ -2150,7 +2159,7 @@ 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);
@@ -2178,6 +2187,7 @@ PerlIO_sv_dup(pTHX_ SV *arg, CLONE_PARAMS *param)
 	return newSVsv(arg);
     }
 #else
+    PERL_UNUSED_ARG(param);
     return newSVsv(arg);
 #endif
 }
@@ -2185,7 +2195,7 @@ PerlIO_sv_dup(pTHX_ SV *arg, CLONE_PARAMS *param)
 PerlIO *
 PerlIOBase_dup(pTHX_ PerlIO *f, PerlIO *o, CLONE_PARAMS *param, int flags)
 {
-    PerlIO *nexto = PerlIONext(o);
+    PerlIO * const nexto = PerlIONext(o);
     if (PerlIOValid(nexto)) {
 	const PerlIO_funcs * const tab = PerlIOBase(nexto)->tab;
 	if (tab && tab->Dup)
@@ -2194,7 +2204,7 @@ 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",
@@ -2419,9 +2429,7 @@ 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;
 }
@@ -2443,7 +2451,7 @@ PerlIOUnix_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
 	    perm = 0666;
 	}
 	if (imode != -1) {
-	    const char *path = SvPV_nolen(*args);
+	    const char *path = SvPV_nolen_const(*args);
 	    fd = PerlLIO_open3(path, imode, perm);
 	}
     }
@@ -2477,7 +2485,7 @@ 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);
@@ -2545,6 +2553,7 @@ PerlIOUnix_write(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 	}
 	PERL_ASYNC_CHECK();
     }
+    /*NOTREACHED*/
 }
 
 Off_t
@@ -2634,9 +2643,10 @@ typedef struct {
 IV
 PerlIOStdio_fileno(pTHX_ PerlIO *f)
 {
-    FILE *s;
-    if (PerlIOValid(f) && (s = PerlIOSelf(f, PerlIOStdio)->stdio)) {
-	return PerlSIO_fileno(s);
+    if (PerlIOValid(f)) {
+	FILE * const s = PerlIOSelf(f, PerlIOStdio)->stdio;
+	if (s)
+	    return PerlSIO_fileno(s);
     }
     errno = EBADF;
     return -1;
@@ -2663,7 +2673,7 @@ PerlIOStdio_pushed(pTHX_ PerlIO *f, const char *mode, SV *arg, PerlIO_funcs *tab
 {
     PerlIO *n;
     if (PerlIOValid(f) && PerlIOValid(n = PerlIONext(f))) {
-        PerlIO_funcs *toptab = PerlIOBase(n)->tab;
+	PerlIO_funcs * const toptab = PerlIOBase(n)->tab;
         if (toptab == tab) {
 	    /* Top is already stdio - pop self (duplicate) and use original */
 	    PerlIO_pop(aTHX_ f);
@@ -2732,8 +2742,8 @@ PerlIOStdio_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
 {
     char tmode[8];
     if (PerlIOValid(f)) {
-	const char *path = SvPV_nolen(*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)),
@@ -2746,7 +2756,7 @@ PerlIOStdio_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
     }
     else {
 	if (narg > 0) {
-	    const char *path = SvPV_nolen(*args);
+	    const char * const path = SvPV_nolen_const(*args);
 	    if (*mode == IoTYPE_NUMERIC) {
 		mode++;
 		fd = PerlLIO_open3(path, imode, perm);
@@ -2809,7 +2819,7 @@ 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);
+		    PerlIOStdio * const s = PerlIOSelf(f, PerlIOStdio);
 		    s->stdio = stdio;
 		    PerlIOUnix_refcnt_inc(fileno(s->stdio));
 		}
@@ -2947,7 +2957,7 @@ PerlIOStdio_invalidate_fileno(pTHX_ FILE *f)
      */
 #    error "Don't know how to set FILE.fileno on your platform"
 #endif
-    (void)f;
+    PERL_UNUSED_ARG(f);
     return 0;
 #  endif
 }
@@ -2955,7 +2965,7 @@ 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;
@@ -3028,7 +3038,7 @@ PerlIOStdio_close(pTHX_ PerlIO *f)
 SSize_t
 PerlIOStdio_read(pTHX_ PerlIO *f, void *vbuf, Size_t count)
 {
-    FILE *s = PerlIOSelf(f, PerlIOStdio)->stdio;
+    FILE * const s = PerlIOSelf(f, PerlIOStdio)->stdio;
     SSize_t got = 0;
     for (;;) {
 	if (count == 1) {
@@ -3059,7 +3069,7 @@ 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)) {
@@ -3131,21 +3141,21 @@ 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;
     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;
     return PerlSIO_ftell(stdio);
 }
 
 IV
 PerlIOStdio_flush(pTHX_ PerlIO *f)
 {
-    FILE *stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
+    FILE * const stdio = PerlIOSelf(f, PerlIOStdio)->stdio;
     if (PerlIOBase(f)->flags & PERLIO_F_CANWRITE) {
 	return PerlSIO_fflush(stdio);
     }
@@ -3160,7 +3170,7 @@ 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
@@ -3200,14 +3210,14 @@ 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
@@ -3216,21 +3226,21 @@ 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 */
@@ -3271,7 +3281,7 @@ 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;
     /*
      * fflush()ing read-only streams can cause trouble on some stdio-s
@@ -3534,12 +3544,16 @@ PerlIOBuf_open(pTHX_ PerlIO_funcs *self, PerlIO_list_t *layers,
 
 /*
  * This "flush" is akin to sfio's sync in that it handles files in either
- * read or write state
+ * read or write state.  For write state, we put the postponed data through
+ * the next layers.  For read state, we seek() the next layers to the
+ * offset given by current position in the buffer, and discard the buffer
+ * state (XXXX supposed to be for seek()able buffers only, but now it is done
+ * in any case?).  Then the pass the stick further in chain.
  */
 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) {
@@ -3593,17 +3607,21 @@ PerlIOBuf_flush(pTHX_ PerlIO *f)
     return code;
 }
 
+/* This discards the content of the buffer after b->ptr, and rereads
+ * the buffer from the position off in the layer downstream; here off
+ * is at offset corresponding to b->ptr - b->buf.
+ */
 IV
 PerlIOBuf_fill(pTHX_ PerlIO *f)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
     PerlIO *n = PerlIONext(f);
     SSize_t avail;
     /*
      * Down-stream flush is defined not to loose read data so is harmless.
      * we would not normally be fill'ing if there was data left in anycase.
      */
-    if (PerlIO_flush(f) != 0)
+    if (PerlIO_flush(f) != 0)	/* XXXX Check that its seek() succeeded?! */
 	return -1;
     if (PerlIOBase(f)->flags & PERLIO_F_TTY)
 	PerlIOBase_flush_linebuf(aTHX);
@@ -3637,7 +3655,7 @@ 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);
@@ -3663,7 +3681,7 @@ 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);
@@ -3675,7 +3693,7 @@ 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)
@@ -3794,7 +3812,7 @@ 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
      */
@@ -3829,8 +3847,7 @@ 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;
 }
@@ -3843,8 +3860,7 @@ 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;
 }
@@ -3852,7 +3868,7 @@ 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;
@@ -3861,7 +3877,7 @@ 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)
@@ -3872,17 +3888,16 @@ PerlIOBuf_get_cnt(pTHX_ PerlIO *f)
 STDCHAR *
 PerlIOBuf_get_base(pTHX_ PerlIO *f)
 {
-    PerlIOBuf *b = PerlIOSelf(f, PerlIOBuf);
+    PerlIOBuf * const b = PerlIOSelf(f, PerlIOBuf);
     if (!b->buf) {
 	if (!b->bufsiz)
 	    b->bufsiz = 4096;
-	b->buf = Newz('B',b->buf,b->bufsiz, STDCHAR);
+	b->buf = Newxz(b->buf,b->bufsiz, STDCHAR);
 	if (!b->buf) {
 	    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;
 }
@@ -3890,7 +3905,7 @@ 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);
@@ -3899,7 +3914,7 @@ 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;
@@ -3988,7 +4003,7 @@ 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;
@@ -4012,7 +4027,7 @@ 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.
@@ -4079,6 +4094,14 @@ PERLIO_FUNCS_DECL(PerlIO_pending) = {
  * crlf - translation On read translate CR,LF to "\n" we do this by
  * overriding ptr/cnt entries to hand back a line at a time and keeping a
  * record of which nl we "lied" about. On write translate "\n" to CR,LF
+ *
+ * c->nl points on the first byte of CR LF pair when it is temporarily
+ * replaced by LF, or to the last CR of the buffer.  In the former case
+ * the caller thinks that the buffer ends at c->nl + 1, in the latter
+ * that it ends at c->nl; these two cases can be distinguished by
+ * *c->nl.  c->nl is set during _getcnt() call, and unset during
+ * _unread() and _flush() calls.
+ * It only matters for read operations.
  */
 
 typedef struct {
@@ -4122,8 +4145,8 @@ 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);
-    if (c->nl) {
+    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;
     }
@@ -4144,7 +4167,7 @@ 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;
@@ -4153,8 +4176,10 @@ PerlIOCrlf_unread(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
 			count--;
 		    }
 		    else {
-			buf++;
-			break;
+		    /* If b->ptr - 1 == b->buf, we are undoing reading 0xa */
+			*--(b->ptr) = 0xa;	/* Works even if 0xa == '\r' */
+			unread++;
+			count--;
 		    }
 		}
 		else {
@@ -4168,14 +4193,15 @@ PerlIOCrlf_unread(pTHX_ PerlIO *f, const void *vbuf, Size_t count)
     }
 }
 
+/* XXXX This code assumes that buffer size >=2, but does not check it... */
 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:
@@ -4243,8 +4269,8 @@ 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) {
@@ -4300,15 +4326,15 @@ 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') {
@@ -4330,8 +4356,7 @@ 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);
@@ -4348,7 +4373,7 @@ 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;
@@ -4426,7 +4451,7 @@ 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);
@@ -4480,10 +4505,10 @@ 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;
@@ -4501,8 +4526,8 @@ 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
@@ -4534,8 +4559,8 @@ 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
@@ -4592,8 +4617,8 @@ 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
@@ -4620,7 +4645,7 @@ 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);
@@ -4634,8 +4659,8 @@ 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;
@@ -4734,8 +4759,8 @@ PerlIO_getname(PerlIO *f, char *buf)
     }
     return name;
 #else
-    (void)f;
-    (void)buf;
+    PERL_UNUSED_ARG(f);
+    PERL_UNUSED_ARG(buf);
     Perl_croak(aTHX_ "Don't know how to get file name");
     return Nullch;
 #endif
@@ -4761,7 +4786,7 @@ PerlIO *
 PerlIO_open(const char *path, const char *mode)
 {
     dTHX;
-    SV *name = sv_2mortal(newSVpvn(path, strlen(path)));
+    SV *name = sv_2mortal(newSVpv(path, 0));
     return PerlIO_openn(aTHX_ Nullch, mode, -1, 0, 0, NULL, 1, &name);
 }
 
@@ -4770,7 +4795,7 @@ PerlIO *
 PerlIO_reopen(const char *path, const char *mode, PerlIO *f)
 {
     dTHX;
-    SV *name = sv_2mortal(newSVpvn(path, strlen(path)));
+    SV *name = sv_2mortal(newSVpv(path,0));
     return PerlIO_openn(aTHX_ Nullch, mode, -1, 0, 0, f, 1, &name);
 }
 
@@ -4813,8 +4838,7 @@ 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
@@ -4831,8 +4855,8 @@ int
 PerlIO_vprintf(PerlIO *f, const char *fmt, va_list ap)
 {
     dTHX;
-    SV *sv = newSVpvn("", 0);
-    char *s;
+    SV * const sv = newSVpvs("");
+    const char *s;
     STRLEN len;
     SSize_t wrote;
 #ifdef NEED_VA_COPY
@@ -4842,7 +4866,7 @@ PerlIO_vprintf(PerlIO *f, const char *fmt, va_list ap)
 #else
     sv_vcatpvf(sv, fmt, &ap);
 #endif
-    s = SvPV(sv, len);
+    s = SvPV_const(sv, len);
     wrote = PerlIO_write(f, s, len);
     SvREFCNT_dec(sv);
     return wrote;
@@ -4885,7 +4909,7 @@ 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
       */
@@ -4898,13 +4922,13 @@ 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);
+	       PerlIOStdio * const s = PerlIOSelf(f, PerlIOStdio);
 
                if (s)
                     s->stdio = stdio;
@@ -4935,7 +4959,7 @@ 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);
     }
@@ -4950,7 +4974,7 @@ 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);