Check if stdio supports tweaking lval and cnt simultaneously.

Subject: PATCH (Re: PerlIO - Configure tweak for Linux/glibc?)
Message-ID: <20001023153932.A10786@plum.flirble.org>

p4raw-id: //depot/perl@7427

22 files changed, 220 insertions, 36 deletions

diff --git a/Configure b/Configure
index 03004beef0..1425389175 100755
--- a/Configure
+++ b/Configure
@@ -20,7 +20,7 @@
 
 # $Id: Head.U,v 3.0.1.9 1997/02/28 15:02:09 ram Exp $
 #
-# Generated on Thu Oct 19 22:28:50 EET DST 2000 [metaconfig 3.0 PL70]
+# Generated on Tue Oct 24 21:00:34 EET DST 2000 [metaconfig 3.0 PL70]
 # (with additional metaconfig patches by perlbug@perl.org)
 
 cat >/tmp/c1$$ <<EOF
@@ -536,6 +536,8 @@ d_fstatvfs=''
 d_statvfs=''
 d_stdio_cnt_lval=''
 d_stdio_ptr_lval=''
+d_stdio_ptr_lval_nochange_cnt=''
+d_stdio_ptr_lval_sets_cnt=''
 d_stdiobase=''
 d_stdstdio=''
 stdio_base=''
@@ -11479,6 +11481,82 @@ esac
 set d_stdio_cnt_lval
 eval $setvar
 
+
+: test whether setting _ptr sets _cnt as a side effect
+d_stdio_ptr_lval_sets_cnt="$undef"
+d_stdio_ptr_lval_nochange_cnt="$undef"
+case "$d_stdio_ptr_lval$d_stdstdio" in
+$define$define)
+	echo "Checking to see what happens if we set the stdio ptr..." >&4
+$cat >try.c <<EOP
+#include <stdio.h>
+/* Can we scream? */
+/* Eat dust sed :-) */
+#define FILE_ptr(fp)	$stdio_ptr
+#define FILE_cnt(fp)	$stdio_cnt
+int main() {
+	FILE *fp = fopen("try.c", "r");
+	char c = getc(fp);
+	char *ptr;
+	size_t cnt;
+	if (!(
+		18 <= FILE_cnt(fp) &&
+		strncmp(FILE_ptr(fp), "include <stdio.h>\n", 18) == 0
+	)) {
+		puts("Fail even to read");
+		exit (1);
+	}
+	ptr = FILE_ptr(fp);
+	cnt = FILE_cnt(fp);
+
+	FILE_ptr(fp)+= 42;
+
+	if (FILE_ptr(fp) != (ptr + 42)) {
+		printf("Fail ptr check %p != %p", FILE_ptr(fp), (ptr + 42));
+		exit (1);
+	}
+	if (FILE_cnt(fp) <= 20) {
+		printf ("Fail (<20 chars to test)");
+		exit (1);
+	}
+	if (strncmp(FILE_ptr(fp), "Eat dust sed :-) */\n", 20) != 0) {
+		puts("Fail compare");
+		exit (1);
+	}
+	if (cnt == FILE_cnt(fp)) {
+		puts("Pass_unchanged");
+		exit (0);
+	}	
+	if (FILE_cnt(fp) == (cnt - 42)) {
+		puts("Pass_changed");
+		exit (0);
+	}
+	printf("Fail count was %d now %d\n", cnt, FILE_cnt(fp));
+	return 1;
+
+}
+EOP
+	set try
+	if eval $compile; then
+ 		case `./try$exe_ext` in
+		Pass_changed)
+			echo "Increasing ptr in your stdio decreases cnt by the same amount. Good." >&4
+			d_stdio_ptr_lval_sets_cnt="$define" ;;
+		Pass_unchanged)
+			echo "Increasing ptr in your stdio leaves cnt unchanged.  Good." >&4
+			d_stdio_ptr_lval_nochange_cnt="$define" ;;
+		Fail*)
+			echo "Increasing ptr in your stdio didn't do exactly what I expected.  We'll not be doing that then." >&4 ;;
+		*)
+			echo "It appears attempting to set ptr in your stdio is a bad plan." >&4 ;;
+	esac
+	else
+		echo "It seems we can't set ptr in your stdio.  Nevermind." >&4
+	fi
+	$rm -f try.c try
+	;;
+esac
+
 : see if _base is also standard
 val="$undef"
 case "$d_stdstdio" in
@@ -15580,6 +15658,8 @@ d_statfs_s='$d_statfs_s'
 d_statvfs='$d_statvfs'
 d_stdio_cnt_lval='$d_stdio_cnt_lval'
 d_stdio_ptr_lval='$d_stdio_ptr_lval'
+d_stdio_ptr_lval_nochange_cnt='$d_stdio_ptr_lval_nochange_cnt'
+d_stdio_ptr_lval_sets_cnt='$d_stdio_ptr_lval_sets_cnt'
 d_stdio_stream_array='$d_stdio_stream_array'
 d_stdiobase='$d_stdiobase'
 d_stdstdio='$d_stdstdio'
diff --git a/Porting/Glossary b/Porting/Glossary
index 1b93821e9b..40e468d56a 100644
--- a/Porting/Glossary
+++ b/Porting/Glossary
@@ -1478,6 +1478,15 @@ d_stdio_ptr_lval (d_stdstdio.U):
 	This variable conditionally defines STDIO_PTR_LVALUE if the
 	FILE_ptr macro can be used as an lvalue.
 
+d_stdio_ptr_lval_nochange_cnt (d_stdstdio.U):
+	This symbol is defined if using the FILE_ptr macro as an lvalue
+	to increase the pointer by n leaves File_cnt(fp) unchanged.
+
+d_stdio_ptr_lval_sets_cnt (d_stdstdio.U):
+	This symbol is defined if using the FILE_ptr macro as an lvalue
+	to increase the pointer by n has the side effect of decreasing the
+	value of File_cnt(fp) by n.
+
 d_stdio_stream_array (stdio_streams.U):
 	This variable tells whether there is an array holding
 	the stdio streams.
diff --git a/Porting/config.sh b/Porting/config.sh
index 632c469288..2c9a49e235 100644
--- a/Porting/config.sh
+++ b/Porting/config.sh
@@ -8,7 +8,7 @@
 
 # Package name      : perl5
 # Source directory  : /m/fs/work/work/permanent/perl/pp4/perl
-# Configuration time: Fri Oct 13 02:12:22 EET DST 2000
+# Configuration time: Tue Oct 24 21:07:39 EET DST 2000
 # Configured by     : jhi
 # Target system     : osf1 alpha.hut.fi v4.0 878 alpha 
 
@@ -62,7 +62,7 @@ ccsymbols='__alpha=1 __LANGUAGE_C__=1 __osf__=1 __unix__=1 _LONGLONG=1 _SYSTYPE_
 ccversion='V5.6-082'
 cf_by='jhi'
 cf_email='yourname@yourhost.yourplace.com'
-cf_time='Fri Oct 13 02:12:22 EET DST 2000'
+cf_time='Tue Oct 24 21:07:39 EET DST 2000'
 charsize='1'
 chgrp=''
 chmod=''
@@ -336,6 +336,8 @@ d_statfs_s='define'
 d_statvfs='define'
 d_stdio_cnt_lval='define'
 d_stdio_ptr_lval='define'
+d_stdio_ptr_lval_nochange_cnt='undef'
+d_stdio_ptr_lval_sets_cnt='undef'
 d_stdio_stream_array='define'
 d_stdiobase='define'
 d_stdstdio='define'
diff --git a/Porting/config_H b/Porting/config_H
index 149760ceaf..3cbfeaebf9 100644
--- a/Porting/config_H
+++ b/Porting/config_H
@@ -17,7 +17,7 @@
 /*
  * Package name      : perl5
  * Source directory  : /m/fs/work/work/permanent/perl/pp4/perl
- * Configuration time: Fri Oct 13 02:12:22 EET DST 2000
+ * Configuration time: Tue Oct 24 21:07:39 EET DST 2000
  * Configured by     : jhi
  * Target system     : osf1 alpha.hut.fi v4.0 878 alpha 
  */
@@ -2028,12 +2028,23 @@
  *	This symbol is defined if the FILE_cnt macro can be used as an
  *	lvalue.
  */
+/* STDIO_PTR_LVAL_SETS_CNT:
+ *	This symbol is defined if using the FILE_ptr macro as an lvalue
+ *	to increase the pointer by n has the side effect of decreasing the
+ *	value of File_cnt(fp) by n.
+ */
+/* STDIO_PTR_LVAL_NOCHANGE_CNT:
+ *	This symbol is defined if using the FILE_ptr macro as an lvalue
+ *	to increase the pointer by n leaves File_cnt(fp) unchanged.
+ */
 #define USE_STDIO_PTR 	/**/
 #ifdef USE_STDIO_PTR
 #define FILE_ptr(fp)	((fp)->_ptr)
 #define STDIO_PTR_LVALUE 		/**/
 #define FILE_cnt(fp)	((fp)->_cnt)
 #define STDIO_CNT_LVALUE 		/**/
+/*#define STDIO_PTR_LVAL_SETS_CNT	/ **/
+/*#define STDIO_PTR_LVAL_NOCHANGE_CNT	/ **/
 #endif
 
 /* USE_STDIO_BASE:
diff --git a/config_h.SH b/config_h.SH
index a209e6d29f..e34d920718 100644
--- a/config_h.SH
+++ b/config_h.SH
@@ -2048,12 +2048,23 @@ sed <<!GROK!THIS! >$CONFIG_H -e 's!^#undef\(.*/\)\*!/\*#define\1 \*!' -e 's!^#un
  *	This symbol is defined if the FILE_cnt macro can be used as an
  *	lvalue.
  */
+/* STDIO_PTR_LVAL_SETS_CNT:
+ *	This symbol is defined if using the FILE_ptr macro as an lvalue
+ *	to increase the pointer by n has the side effect of decreasing the
+ *	value of File_cnt(fp) by n.
+ */
+/* STDIO_PTR_LVAL_NOCHANGE_CNT:
+ *	This symbol is defined if using the FILE_ptr macro as an lvalue
+ *	to increase the pointer by n leaves File_cnt(fp) unchanged.
+ */
 #$d_stdstdio USE_STDIO_PTR 	/**/
 #ifdef USE_STDIO_PTR
 #define FILE_ptr(fp)	$stdio_ptr
 #$d_stdio_ptr_lval STDIO_PTR_LVALUE 		/**/
 #define FILE_cnt(fp)	$stdio_cnt
 #$d_stdio_cnt_lval STDIO_CNT_LVALUE 		/**/
+#$d_stdio_ptr_lval_sets_cnt STDIO_PTR_LVAL_SETS_CNT	/**/
+#$d_stdio_ptr_lval_nochange_cnt STDIO_PTR_LVAL_NOCHANGE_CNT	/**/
 #endif
 
 /* USE_STDIO_BASE:
diff --git a/configure.com b/configure.com
index f4b607aded..84f07def8d 100644
--- a/configure.com
+++ b/configure.com
@@ -4373,7 +4373,6 @@ $   d_mbstowcs="define"
 $   d_mbtowc="define"
 $   d_stdiobase="define"
 $   d_stdio_cnt_lval="define"
-$   d_stdio_ptr_lval="define"
 $   d_stdstdio="define"
 $   d_wcstombs="define"
 $   d_mblen="define"
@@ -4402,6 +4401,8 @@ $   i_locale="undef"
 $   d_locconv="undef"
 $   d_setlocale="undef"
 $ ENDIF
+$ d_stdio_ptr_lval_sets_cnt="undef"
+$ d_stdio_ptr_lval_nochange_cnt="undef"
 $!
 $! Sockets?
 $ if Has_Socketshr .OR. Has_Dec_C_Sockets
@@ -4935,6 +4936,8 @@ $ WC "d_statfs_s='undef'"
 $ WC "d_statfsflags='undef'"
 $ WC "d_stdio_cnt_lval='" + d_stdio_cnt_lval + "'"
 $ WC "d_stdio_ptr_lval='" + d_stdio_ptr_lval + "'"
+$ WC "d_stdio_ptr_lval_sets_cnt='" + d_stdio_ptr_lval_sets_cnt + "'"
+$ WC "d_stdio_ptr_lval_nochange_cnt='" + d_stdio_ptr_lval_nochange_cnt + "'"
 $ WC "d_stdio_stream_array='undef'"
 $ WC "d_stdiobase='" + d_stdiobase + "'"
 $ WC "d_stdstdio='" + d_stdstdio + "'"
diff --git a/epoc/config.sh b/epoc/config.sh
index ee65ee35ce..e760d671cf 100644
--- a/epoc/config.sh
+++ b/epoc/config.sh
@@ -324,6 +324,8 @@ d_statfsflags='define'
 d_statvfs='undef'
 d_stdio_cnt_lval='define'
 d_stdio_ptr_lval='define'
+d_stdio_ptr_lval_sets_cnt='undef'
+d_stdio_ptr_lval_nochange_cnt='undef'
 d_stdio_stream_array='undef'
 d_stdiobase='undef'
 d_stdstdio='undef'
diff --git a/iperlsys.h b/iperlsys.h
index 59da4748cb..6844801bb4 100644
--- a/iperlsys.h
+++ b/iperlsys.h
@@ -186,13 +186,19 @@ struct IPerlStdIOInfo
 
 #ifdef USE_STDIO_PTR
 #  define PerlIO_has_cntptr(f)		1       
-#  ifdef STDIO_CNT_LVALUE
-#    define PerlIO_canset_cnt(f)	1      
-#    ifdef STDIO_PTR_LVALUE
+#  ifdef STDIO_PTR_LVALUE
+#    ifdef  STDIO_CNT_LVALUE
+#      define PerlIO_canset_cnt(f)	1      
+#      ifdef STDIO_PTR_LVAL_NOCHANGE_CNT
+#        define PerlIO_fast_gets(f)	1        
+#      endif
+#    else /* STDIO_CNT_LVALUE */
+#      define PerlIO_canset_cnt(f)	0      
+#    endif
+#  else /* STDIO_PTR_LVALUE */
+#    ifdef STDIO_PTR_LVAL_SETS_CNT
 #      define PerlIO_fast_gets(f)	1        
 #    endif
-#  else
-#    define PerlIO_canset_cnt(f)	0      
 #  endif
 #else  /* USE_STDIO_PTR */
 #  define PerlIO_has_cntptr(f)		0
diff --git a/perlio.c b/perlio.c
index a88daa5e02..969b8d1c6d 100644
--- a/perlio.c
+++ b/perlio.c
@@ -176,10 +176,14 @@ PerlIO_set_ptrcnt(PerlIO *f, STDCHAR *ptr, int cnt)
 #else
   Perl_croak(aTHX_ "Cannot set 'ptr' of FILE * on this system");
 #endif
-#if defined(USE_STDIO_PTR) && defined(STDIO_CNT_LVALUE)
+#if defined(USE_STDIO_PTR) && defined(STDIO_CNT_LVALUE) && defined (STDIO_PTR_LVAL_NOCHANGE_CNT)
   FILE_cnt(f) = cnt;
 #else
-  Perl_croak(aTHX_ "Cannot set 'cnt' of FILE * on this system");
+#if defined(STDIO_PTR_LVAL_SETS_CNT)
+  assert (FILE_cnt(f) == cnt);
+#else
+  Perl_croak(aTHX_ "Cannot set 'cnt' of FILE * on this system when setting 'ptr'");
+#endif
 #endif
 }
 
diff --git a/perlsdio.h b/perlsdio.h
index c4a1179a41..90ca5345fb 100644
--- a/perlsdio.h
+++ b/perlsdio.h
@@ -97,20 +97,30 @@
 
 #ifdef STDIO_CNT_LVALUE
 #define PerlIO_canset_cnt(f)		1      
+#define PerlIO_set_cnt(f,c)		(FILE_cnt(f) = (c))          
 #ifdef STDIO_PTR_LVALUE
+#ifdef STDIO_PTR_LVAL_NOCHANGE_CNT
 #define PerlIO_fast_gets(f)		1        
 #endif
-#define PerlIO_set_cnt(f,c)		(FILE_cnt(f) = (c))          
-#else
+#endif /* STDIO_PTR_LVALUE */
+#else /* STDIO_CNT_LVALUE */
 #define PerlIO_canset_cnt(f)		0      
 #define PerlIO_set_cnt(f,c)		abort()
 #endif
 
 #ifdef STDIO_PTR_LVALUE
-#define PerlIO_set_ptrcnt(f,p,c)	(FILE_ptr(f) = (p), PerlIO_set_cnt(f,c))          
+#ifdef STDIO_PTR_LVAL_NOCHANGE_CNT
+#define PerlIO_set_ptrcnt(f,p,c)	STMT_START {FILE_ptr(f) = (p), PerlIO_set_cnt(f,c)} STMT_END
+#else
+#ifdef STDIO_PTR_LVAL_SETS_CNT
+/* assert() may pre-process to ""; potential syntax error (FILE_ptr(), ) */
+#define PerlIO_set_ptrcnt(f,p,c)	STMT_START {FILE_ptr(f) = (p); assert(FILE_cnt(f) == (c))} STMT_END
+#define PerlIO_fast_gets(f)		1        
 #else
 #define PerlIO_set_ptrcnt(f,p,c)	abort()
 #endif
+#endif
+#endif
 
 #else  /* USE_STDIO_PTR */
 
diff --git a/perlsfio.h b/perlsfio.h
index d0f6471659..a736371a32 100644
--- a/perlsfio.h
+++ b/perlsfio.h
@@ -52,10 +52,10 @@ extern int	_stdprintf _ARG_((const char*, ...));
 #define PerlIO_has_cntptr(f)		1       
 #define PerlIO_get_ptr(f)		((f)->next)
 #define PerlIO_get_cnt(f)		((f)->endr - (f)->next)
-#define PerlIO_canset_cnt(f)		1      
-#define PerlIO_fast_gets(f)		1        
-#define PerlIO_set_ptrcnt(f,p,c)	((f)->next = (unsigned char *)(p))          
-#define PerlIO_set_cnt(f,c)		1
+#define PerlIO_canset_cnt(f)		0
+#define PerlIO_fast_gets(f)		1
+#define PerlIO_set_ptrcnt(f,p,c)	STMT_START {(f)->next = (unsigned char *)(p); assert(FILE_cnt(f) == (c))} STMT_END
+#define PerlIO_set_cnt(f,c)		Perl_croak(aTHX_ "Cannot set 'cnt' of FILE * on this system");
 
 #define PerlIO_has_base(f)		1         
 #define PerlIO_get_base(f)		((f)->data)
diff --git a/pod/Makefile.SH b/pod/Makefile.SH
index ae6262c816..efc6ac2e49 100644
--- a/pod/Makefile.SH
+++ b/pod/Makefile.SH
@@ -73,7 +73,9 @@ converters: $(CONVERTERS)
 regen_pods: perlmodlib.pod toc
 
 buildtoc:	buildtoc.PL perl.pod ../MANIFEST
-	$(PERL) -I ../lib buildtoc.PL
+	$(PERL) buildtoc.PL
+
+perltoc.pod:	buildtoc
 
 man:	pod2man $(MAN)
 
@@ -82,7 +84,7 @@ html:	pod2html $(HTML)
 tex:	pod2latex $(TEX)
 
 toc:	buildtoc
-	$(PERL) -I../lib buildtoc
+	$(PERL) buildtoc
 
 .SUFFIXES: .pm .pod
 
diff --git a/pod/perltoc.pod b/pod/perltoc.pod
index b87b3ab6d9..417451255a 100644
--- a/pod/perltoc.pod
+++ b/pod/perltoc.pod
@@ -4149,9 +4149,9 @@ B<filter_fetch_value>
 AvFILL, av_clear, av_delete, av_exists, av_extend, av_fetch, av_fill,
 av_len, av_make, av_pop, av_push, av_shift, av_store, av_undef, av_unshift,
 bytes_to_utf8, call_argv, call_method, call_pv, call_sv, CLASS, Copy,
-croak, CvSTASH, dMARK, dORIGMARK, dSP, dXSARGS, dXSI32, ENTER, eval_pv,
-eval_sv, EXTEND, fbm_compile, fbm_instr, FREETMPS, get_av, get_cv, get_hv,
-get_sv, GIMME, GIMME_V, GvSV, gv_fetchmeth, gv_fetchmethod,
+croak, CvSTASH, cv_const_sv, dMARK, dORIGMARK, dSP, dXSARGS, dXSI32, ENTER,
+eval_pv, eval_sv, EXTEND, fbm_compile, fbm_instr, FREETMPS, get_av, get_cv,
+get_hv, get_sv, GIMME, GIMME_V, GvSV, gv_fetchmeth, gv_fetchmethod,
 gv_fetchmethod_autoload, gv_stashpv, gv_stashsv, G_ARRAY, G_DISCARD,
 G_EVAL, G_NOARGS, G_SCALAR, G_VOID, HEf_SVKEY, HeHASH, HeKEY, HeKLEN, HePV,
 HeSVKEY, HeSVKEY_force, HeSVKEY_set, HeVAL, HvNAME, hv_clear, hv_delete,
@@ -6879,7 +6879,7 @@ FILL, MAX, OFF, ARRAY, AvFLAGS
 =item B::CV METHODS
 
 STASH, START, ROOT, GV, FILE, DEPTH, PADLIST, OUTSIDE, XSUB, XSUBANY,
-CvFLAGS
+CvFLAGS, const_sv
 
 =item B::HV METHODS
 
@@ -9217,21 +9217,21 @@ pasthru (o)
 
 =item Using Attributes and Parameters
 
-AUTHOR, ABSTRACT, ABSTRACT_FROM, BINARY_LOCATION, C, CAPI, CCFLAGS, CONFIG,
+ABSTRACT, ABSTRACT_FROM, AUTHOR, BINARY_LOCATION, C, CAPI, CCFLAGS, CONFIG,
 CONFIGURE, DEFINE, DIR, DISTNAME, DL_FUNCS, DL_VARS, EXCLUDE_EXT,
 EXE_FILES, FIRST_MAKEFILE, FULLPERL, FUNCLIST, H, HTMLLIBPODS,
 HTMLSCRIPTPODS, IMPORTS, INC, INCLUDE_EXT, INSTALLARCHLIB, INSTALLBIN,
 INSTALLDIRS, INSTALLHTMLPRIVLIBDIR, INSTALLHTMLSCRIPTDIR,
 INSTALLHTMLSITELIBDIR, INSTALLMAN1DIR, INSTALLMAN3DIR, INSTALLPRIVLIB,
 INSTALLSCRIPT, INSTALLSITEARCH, INSTALLSITELIB, INST_ARCHLIB, INST_BIN,
-INST_EXE, INST_LIB, INST_HTMLLIBDIR, INST_HTMLSCRIPTDIR, INST_MAN1DIR,
-INST_MAN3DIR, INST_SCRIPT, PERL_MALLOC_OK, LDFROM, LIB, LIBPERL_A, LIBS,
-LINKTYPE, MAKEAPERL, MAKEFILE, MAN1PODS, MAN3PODS, MAP_TARGET, MYEXTLIB,
-NAME, NEEDS_LINKING, NOECHO, NORECURS, NO_VC, OBJECT, OPTIMIZE, PERL,
-PERLMAINCC, PERL_ARCHLIB, PERL_LIB, PERL_SRC, PERM_RW, PERM_RWX, PL_FILES,
-PM, PMLIBDIRS, POLLUTE, PPM_INSTALL_EXEC, PPM_INSTALL_SCRIPT, PREFIX,
-PREREQ_PM, SKIP, TYPEMAPS, VERSION, VERSION_FROM, XS, XSOPT, XSPROTOARG,
-XS_VERSION
+INST_EXE, INST_HTMLLIBDIR, INST_HTMLSCRIPTDIR, INST_LIB, INST_MAN1DIR,
+INST_MAN3DIR, INST_SCRIPT, LDFROM, LIB, LIBPERL_A, LIBS, LINKTYPE,
+MAKEAPERL, MAKEFILE, MAN1PODS, MAN3PODS, MAP_TARGET, MYEXTLIB, NAME,
+NEEDS_LINKING, NOECHO, NORECURS, NO_VC, OBJECT, OPTIMIZE, PERL, PERLMAINCC,
+PERL_ARCHLIB, PERL_LIB, PERL_MALLOC_OK, PERL_SRC, PERM_RW, PERM_RWX,
+PL_FILES, PM, PMLIBDIRS, POLLUTE, PPM_INSTALL_EXEC, PPM_INSTALL_SCRIPT,
+PREFIX, PREREQ_PM, SKIP, TYPEMAPS, VERSION, VERSION_FROM, XS, XSOPT,
+XSPROTOARG, XS_VERSION
 
 =item Additional lowercase attributes
 
diff --git a/uconfig.h b/uconfig.h
index 96d3264618..67cc252e2b 100644
--- a/uconfig.h
+++ b/uconfig.h
@@ -2024,12 +2024,23 @@
  *	This symbol is defined if the FILE_cnt macro can be used as an
  *	lvalue.
  */
+/* STDIO_PTR_LVAL_SETS_CNT:
+ *	This symbol is defined if using the FILE_ptr macro as an lvalue
+ *	to increase the pointer by n has the side effect of decreasing the
+ *	value of File_cnt(fp) by n.
+ */
+/* STDIO_PTR_LVAL_NOCHANGE_CNT:
+ *	This symbol is defined if using the FILE_ptr macro as an lvalue
+ *	to increase the pointer by n leaves File_cnt(fp) unchanged.
+ */
 /*#define USE_STDIO_PTR 	/ **/
 #ifdef USE_STDIO_PTR
 #define FILE_ptr(fp)	((fp)->_IO_read_ptr)
-/*#define STDIO_PTR_LVALUE 		/ **/
+# STDIO_PTR_LVALUE 		/**/
 #define FILE_cnt(fp)	((fp)->_IO_read_end - (fp)->_IO_read_ptr)
 /*#define STDIO_CNT_LVALUE 		/ **/
+/*#define STDIO_PTR_LVAL_SETS_CNT	/ **/
+/*#define STDIO_PTR_LVAL_NOCHANGE_CNT	/ **/
 #endif
 
 /* USE_STDIO_BASE:
diff --git a/uconfig.sh b/uconfig.sh
index faf618a955..eb8e052437 100755
--- a/uconfig.sh
+++ b/uconfig.sh
@@ -254,7 +254,8 @@ d_statfs_f_flags='undef'
 d_statfs_s='undef'
 d_statvfs='undef'
 d_stdio_cnt_lval='undef'
-d_stdio_ptr_lval='undef'
+d_stdio_ptr_lval_sets_cnt='undef'
+d_stdio_ptr_lval_nochange_cnt='undef'
 d_stdio_stream_array='undef'
 d_stdiobase='undef'
 d_stdstdio='undef'
diff --git a/vms/genconfig.pl b/vms/genconfig.pl
index e500e760a2..ef1d5ad4a5 100644
--- a/vms/genconfig.pl
+++ b/vms/genconfig.pl
@@ -229,6 +229,8 @@ foreach (@ARGV) {
                  d_wcstombs d_wctomb d_mblen d_mktime d_strcoll d_strxfrm ]) {
       print OUT "$_='$rtlhas'\n";
     }
+    print OUT "d_stdio_ptr_lval_sets_cnt='undef'\n";
+    print OUT "d_stdio_ptr_lval_nochange_cnt='undef'\n";
     foreach (qw[ d_gettimeod d_uname d_truncate d_wait4 d_index
                  d_pathconf d_fpathconf d_sysconf d_sigsetjmp ]) {
       print OUT "$_='$rtlnew'\n";
diff --git a/vos/config.def b/vos/config.def
index 4edc806b9c..0f67dee19a 100644
--- a/vos/config.def
+++ b/vos/config.def
@@ -238,6 +238,8 @@ $d_statfs_f_flags='undef'
 $d_statfs_s='undef'
 $d_stdio_cnt_lval='define'
 $d_stdio_ptr_lval='define'
+$d_stdio_ptr_lval_sets_cnt='undef'
+$d_stdio_ptr_lval_nochange_cnt='undef'
 $d_stdio_stream_array='define'
 $d_stdiobase='define'
 $d_stdstdio='define'
diff --git a/vos/config.h b/vos/config.h
index 985e6ea5bc..5c1e020e45 100644
--- a/vos/config.h
+++ b/vos/config.h
@@ -2024,12 +2024,23 @@
  *	This symbol is defined if the FILE_cnt macro can be used as an
  *	lvalue.
  */
+/* STDIO_PTR_LVAL_SETS_CNT:
+ *	This symbol is defined if using the FILE_ptr macro as an lvalue
+ *	to increase the pointer by n has the side effect of decreasing the
+ *	value of File_cnt(fp) by n.
+ */
+/* STDIO_PTR_LVAL_NOCHANGE_CNT:
+ *	This symbol is defined if using the FILE_ptr macro as an lvalue
+ *	to increase the pointer by n leaves File_cnt(fp) unchanged.
+ */
 #define USE_STDIO_PTR 	/**/
 #ifdef USE_STDIO_PTR
 #define FILE_ptr(fp)	((fp)->_ptr)
 #define STDIO_PTR_LVALUE 		/**/
 #define FILE_cnt(fp)	((fp)->_cnt)
 #define STDIO_CNT_LVALUE 		/**/
+/*#define STDIO_PTR_LVAL_SETS_CNT	/**/
+/*#define STDIO_PTR_LVAL_NOCHANGE_CNT	/**/
 #endif
 
 /* USE_STDIO_BASE:
diff --git a/vos/config_h.SH_orig b/vos/config_h.SH_orig
index a209e6d29f..e34d920718 100755
--- a/vos/config_h.SH_orig
+++ b/vos/config_h.SH_orig
@@ -2048,12 +2048,23 @@ sed <<!GROK!THIS! >$CONFIG_H -e 's!^#undef\(.*/\)\*!/\*#define\1 \*!' -e 's!^#un
  *	This symbol is defined if the FILE_cnt macro can be used as an
  *	lvalue.
  */
+/* STDIO_PTR_LVAL_SETS_CNT:
+ *	This symbol is defined if using the FILE_ptr macro as an lvalue
+ *	to increase the pointer by n has the side effect of decreasing the
+ *	value of File_cnt(fp) by n.
+ */
+/* STDIO_PTR_LVAL_NOCHANGE_CNT:
+ *	This symbol is defined if using the FILE_ptr macro as an lvalue
+ *	to increase the pointer by n leaves File_cnt(fp) unchanged.
+ */
 #$d_stdstdio USE_STDIO_PTR 	/**/
 #ifdef USE_STDIO_PTR
 #define FILE_ptr(fp)	$stdio_ptr
 #$d_stdio_ptr_lval STDIO_PTR_LVALUE 		/**/
 #define FILE_cnt(fp)	$stdio_cnt
 #$d_stdio_cnt_lval STDIO_CNT_LVALUE 		/**/
+#$d_stdio_ptr_lval_sets_cnt STDIO_PTR_LVAL_SETS_CNT	/**/
+#$d_stdio_ptr_lval_nochange_cnt STDIO_PTR_LVAL_NOCHANGE_CNT	/**/
 #endif
 
 /* USE_STDIO_BASE:
diff --git a/win32/config.bc b/win32/config.bc
index 097d4290ab..afc148c252 100644
--- a/win32/config.bc
+++ b/win32/config.bc
@@ -319,6 +319,8 @@ d_statfs_s='undef'
 d_statvfs='undef'
 d_stdio_cnt_lval='define'
 d_stdio_ptr_lval='define'
+d_stdio_ptr_lval_sets_cnt='undef'
+d_stdio_ptr_lval_nochange_cnt='undef'
 d_stdio_stream_array='undef'
 d_stdiobase='define'
 d_stdstdio='define'
diff --git a/win32/config.gc b/win32/config.gc
index 9251b24f3d..b196486825 100644
--- a/win32/config.gc
+++ b/win32/config.gc
@@ -319,6 +319,8 @@ d_statfs_s='undef'
 d_statvfs='undef'
 d_stdio_cnt_lval='define'
 d_stdio_ptr_lval='define'
+d_stdio_ptr_lval_sets_cnt='undef'
+d_stdio_ptr_lval_nochange_cnt='undef'
 d_stdio_stream_array='undef'
 d_stdiobase='define'
 d_stdstdio='define'
diff --git a/win32/config.vc b/win32/config.vc
index 61558e5612..071b4649ec 100644
--- a/win32/config.vc
+++ b/win32/config.vc
@@ -319,6 +319,8 @@ d_statfs_s='undef'
 d_statvfs='undef'
 d_stdio_cnt_lval='define'
 d_stdio_ptr_lval='define'
+d_stdio_ptr_lval_sets_cnt='undef'
+d_stdio_ptr_lval_nochange_cnt='undef'
 d_stdio_stream_array='undef'
 d_stdiobase='define'
 d_stdstdio='define'