Import Dev86-0.0.4.tar.gzv0.0.4

11 files changed, 239 insertions, 118 deletions

diff --git a/ld/Makefile b/ld/Makefile
index 756a25c..d93579a 100644
--- a/ld/Makefile
+++ b/ld/Makefile
@@ -1,13 +1,24 @@
-CFLAGS		=-O -DBSD_A_OUT -DSTANDARD_GNU_A_OUT
-LDFLAGS		=-N -s
+
+ifneq ($(TOPDIR),)
+include $(TOPDIR)/Make.defs
+else
+CC=bcc
+LDFLAGS=-s
+endif
 
 OBJS		=dumps.o io.o ld.o readobj.o table.o typeconv.o writebin.o
 
-ld: $(OBJS)
+all: ld86
+
+ld86: $(OBJS)
 	$(CC) $(LDFLAGS) $(OBJS) -o $@
 
+install: ld86
+	install -d $(LIBDIR)
+	install -m 755 ld86 $(LIBDIR)
+
 clean:
-	rm -f $(OBJS) ld
+	rm -f $(OBJS) ld86
 
 dumps.o: dumps.c const.h config.h obj.h type.h globvar.h
 io.o: io.c const.h config.h obj.h type.h globvar.h
diff --git a/ld/Makefile.minix b/ld/Makefile.minix
deleted file mode 100644
index 7f819fa..0000000
--- a/ld/Makefile.minix
+++ /dev/null
@@ -1,20 +0,0 @@
-CFLAGS		=-O -DBSD_A_OUT
-LDFLAGS		=
-
-OBJS		=dumps.o io.o ld.o readobj.o table.o typeconv.o writebin.o
-
-ld: $(OBJS)
-	$(CC) $(LDFLAGS) $(OBJS) -o $@
-	chmem =232000 $@
-
-clean:
-	rm -f $(OBJS) ld
-
-dumps.o: dumps.c const.h config.h obj.h type.h globvar.h
-io.o: io.c const.h config.h obj.h type.h globvar.h
-ld.o: ld.c const.h config.h byteord.h type.h globvar.h
-readobj.o: readobj.c ar.h const.h config.h byteord.h obj.h type.h globvar.h
-table.o: table.c const.h config.h align.h obj.h type.h globvar.h
-typeconv.o: typeconv.c const.h config.h type.h globvar.h
-writebin.o: writebin.c bsd-a.out.h a.out.gnu.h const.h config.h obj.h type.h \
-  globvar.h
diff --git a/ld/a.out.h b/ld/a.out.h
new file mode 100644
index 0000000..f6a7b94
--- /dev/null
+++ b/ld/a.out.h
@@ -0,0 +1,115 @@
+/* Copyright (C) 1990-1996 
+ * This file is part of the ld86 command for Linux-86 
+ * It is distributed under the GNU Library General Public License.
+ *
+ * - This may actually be BSD or Minix code, can someone clarify please. -RDB
+ */
+
+#ifndef __AOUT_H
+#define __AOUT_H
+
+struct	exec {			/* a.out header */
+  unsigned char	a_magic[2];	/* magic number */
+  unsigned char	a_flags;	/* flags, see below */
+  unsigned char	a_cpu;		/* cpu id */
+  unsigned char	a_hdrlen;	/* length of header */
+  unsigned char	a_unused;	/* reserved for future use */
+  unsigned short a_version;	/* version stamp (not used at present) */
+  long		a_text;		/* size of text segement in bytes */
+  long		a_data;		/* size of data segment in bytes */
+  long		a_bss;		/* size of bss segment in bytes */
+  long		a_entry;	/* entry point */
+  long		a_total;	/* total memory allocated */
+  long		a_syms;		/* size of symbol table */
+
+  /* SHORT FORM ENDS HERE */
+  long		a_trsize;	/* text relocation size */
+  long		a_drsize;	/* data relocation size */
+  long		a_tbase;	/* text relocation base */
+  long		a_dbase;	/* data relocation base */
+};
+
+#define A_MAGIC0      (unsigned char) 0x01
+#define A_MAGIC1      (unsigned char) 0x03
+#define BADMAG(X)     ((X).a_magic[0] != A_MAGIC0 ||(X).a_magic[1] != A_MAGIC1)
+
+/* CPU Id of TARGET machine (byte order coded in low order two bits) */
+#define A_NONE	0x00	/* unknown */
+#define A_I8086	0x04	/* intel i8086/8088 */
+#define A_M68K	0x0B	/* motorola m68000 */
+#define A_NS16K	0x0C	/* national semiconductor 16032 */
+#define A_I80386 0x10	/* intel i80386 */
+#define A_SPARC	0x17	/* Sun SPARC */
+
+#define A_BLR(cputype)	((cputype&0x01)!=0) /* TRUE if bytes left-to-right */
+#define A_WLR(cputype)	((cputype&0x02)!=0) /* TRUE if words left-to-right */
+
+/* Flags. */
+#define A_UZP	0x01	/* unmapped zero page (pages) */
+#define A_PAL	0x02	/* page aligned executable */
+#define A_NSYM	0x04	/* new style symbol table */
+#define A_EXEC	0x10	/* executable */
+#define A_SEP	0x20	/* separate I/D */
+#define A_PURE	0x40	/* pure text */
+#define A_TOVLY	0x80	/* text overlay */
+
+/* Offsets of various things. */
+#define A_MINHDR	32
+#define	A_TEXTPOS(X)	((long)(X).a_hdrlen)
+#define A_DATAPOS(X)	(A_TEXTPOS(X) + (X).a_text)
+#define	A_HASRELS(X)	((X).a_hdrlen > (unsigned char) A_MINHDR)
+#define A_HASEXT(X)	((X).a_hdrlen > (unsigned char) (A_MINHDR +  8))
+#define A_HASLNS(X)	((X).a_hdrlen > (unsigned char) (A_MINHDR + 16))
+#define A_HASTOFF(X)	((X).a_hdrlen > (unsigned char) (A_MINHDR + 24))
+#define A_TRELPOS(X)	(A_DATAPOS(X) + (X).a_data)
+#define A_DRELPOS(X)	(A_TRELPOS(X) + (X).a_trsize)
+#define A_SYMPOS(X)	(A_TRELPOS(X) + (A_HASRELS(X) ? \
+  			((X).a_trsize + (X).a_drsize) : 0))
+
+struct reloc {
+  long r_vaddr;			/* virtual address of reference */
+  unsigned short r_symndx;	/* internal segnum or extern symbol num */
+  unsigned short r_type;	/* relocation type */
+};
+
+/* r_tyep values: */
+#define R_ABBS		0
+#define R_RELLBYTE	2
+#define R_PCRBYTE	3
+#define R_RELWORD	4
+#define R_PCRWORD	5
+#define R_RELLONG	6
+#define R_PCRLONG	7
+#define R_REL3BYTE	8
+#define R_KBRANCHE	9
+
+/* r_symndx for internal segments */
+#define S_ABS		((unsigned short)-1)
+#define S_TEXT		((unsigned short)-2)
+#define S_DATA		((unsigned short)-3)
+#define S_BSS		((unsigned short)-4)
+
+struct nlist {			/* symbol table entry */
+  char n_name[24];		/* symbol name */
+  long n_value;			/* value */
+  unsigned char	n_sclass;	/* storage class */
+  unsigned char	n_numaux;	/* number of auxiliary entries (not used) */
+  unsigned short n_type;	/* language base and derived type (not used) */
+};
+
+/* Low bits of storage class (section). */
+#define	N_SECT		  07	/* section mask */
+#define N_UNDF		  00	/* undefined */
+#define N_ABS		  01	/* absolute */
+#define N_TEXT		  02	/* text */
+#define N_DATA		  03	/* data */
+#define	N_BSS		  04	/* bss */
+#define N_COMM		  05	/* (common) */
+
+/* High bits of storage class. */
+#define N_CLASS		0370	/* storage class mask */
+#define C_NULL
+#define C_EXT		0020	/* external symbol */
+#define C_STAT		0030	/* static */
+
+#endif /* _AOUT_H */
diff --git a/ld/const.h b/ld/const.h
index 7705e15..04d6330 100644
--- a/ld/const.h
+++ b/ld/const.h
@@ -3,7 +3,7 @@
 /* Copyright (C) 1994 Bruce Evans */
 
 #define FALSE	0
-#define NULL	0
+#define NUL_PTR	((void*)0)
 #define TRUE	1
 
 #define EXTERN	extern
diff --git a/ld/dumps.c b/ld/dumps.c
index 5027fac..c9a40d4 100644
--- a/ld/dumps.c
+++ b/ld/dumps.c
@@ -13,7 +13,7 @@ PUBLIC void dumpmods()
 {
     struct modstruct *modptr;
 
-    for (modptr = modfirst; modptr != NULL; modptr = modptr->modnext)
+    for (modptr = modfirst; modptr != NUL_PTR; modptr = modptr->modnext)
     {
 	putstr(modptr->loadflag ? "L " : "  ");
 	putbstr(20, modptr->modname);
@@ -31,11 +31,11 @@ PUBLIC void dumpsyms()
     struct symstruct *symptr;
     char uflag;
 
-    for (modptr = modfirst; modptr != NULL; modptr = modptr->modnext)
+    for (modptr = modfirst; modptr != NUL_PTR; modptr = modptr->modnext)
 	if (modptr->loadflag)
 	{
 	    for (symparray = modptr->symparray;
-		 (symptr = *symparray) != NULL; ++symparray)
+		 (symptr = *symparray) != NUL_PTR; ++symparray)
 		if (symptr->modptr == modptr)
 		{
 		    uflag = FALSE;
diff --git a/ld/include/fcntl.h b/ld/include/fcntl.h
new file mode 100644
index 0000000..8c1ec8b
--- /dev/null
+++ b/ld/include/fcntl.h
@@ -0,0 +1,2 @@
+#define O_RDONLY	0
+#define O_WRONLY	1
diff --git a/ld/io.c b/ld/io.c
index aef49d0..c1829c8 100644
--- a/ld/io.c
+++ b/ld/io.c
@@ -6,20 +6,19 @@
 #include "obj.h"		/* needed for LONG_OFFSETS and offset_t */
 #include "type.h"
 #include "globvar.h"
+#include <fcntl.h>
 
 #ifdef STDC_HEADERS_MISSING
 void exit P((int status));
 void *malloc P((unsigned size));
 #else
-#undef NULL
 #include <stdlib.h>
 #endif
 
 #ifdef POSIX_HEADERS_MISSING
-#define O_RDONLY	0
-#define O_WRONLY	1
 #define SEEK_SET	0
 #define STDOUT_FILENO	0
+#include <sys/types.h>
 #include <sys/stat.h>
 #define mode_t		unsigned short
 #define off_t		long
@@ -33,7 +32,6 @@ int read P((int fd, void *buf, unsigned nbytes));
 mode_t umask P((int oldmask));
 int write P((int fd, const void *buf, unsigned nbytes));
 #else
-#undef NULL
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -46,6 +44,9 @@ int write P((int fd, const void *buf, unsigned nbytes));
 #define INBUFSIZE	1024
 #define OUTBUFSIZE	2048
 #define TRELBUFSIZE	1024
+#ifndef O_BINARY
+#define O_BINARY 0
+#endif
 
 #ifdef BSD_A_OUT
 PRIVATE char *drelbuf;		/* extra output buffer for data relocations */
@@ -197,7 +198,7 @@ char *filename;
     {
 	closein();
 	inputname = filename;	/* this relies on filename being static */
-	if ((infd = open(filename, O_RDONLY)) < 0)
+	if ((infd = open(filename, O_BINARY|O_RDONLY)) < 0)
 	    inputerror("cannot open");
 	inbufptr = inbufend = inbuf;
     }
@@ -209,7 +210,7 @@ char *filename;
     struct stat statbuf;
 
     outputname = filename;
-    if ((outfd = creat(filename, CREAT_PERMS)) == ERR)
+    if ((outfd = open(filename, O_BINARY|O_RDWR|O_CREAT|O_TRUNC, CREAT_PERMS)) == ERR)
 	outputerror("cannot open");
     if (fstat(outfd, &statbuf) != 0) 
 	outputerror("cannot stat");
@@ -220,7 +221,7 @@ char *filename;
 #endif
     outbufptr = outbuf;
 #ifdef BSD_A_OUT
-    if ((trelfd = open(filename, O_WRONLY)) == ERR)
+    if ((trelfd = open(filename, O_BINARY|O_WRONLY|O_CREAT|O_TRUNC, CREAT_PERMS)) == ERR)
 	outputerror("cannot reopen");
     trelbufptr = trelbuf;
 #endif
@@ -528,7 +529,7 @@ char *defarchentry;
     putstr(message);
     putstr(" in file ");
     putstr(inputname);
-    if (archentry != NULL)
+    if (archentry != NUL_PTR)
     {
 	putbyte('(');
 	putstr(archentry);
@@ -536,7 +537,7 @@ char *defarchentry;
     }
     putstr("; using definition in ");
     putstr(deffilename);
-    if (defarchentry != NULL)
+    if (defarchentry != NUL_PTR)
     {
 	putbyte('(');
 	putstr(defarchentry);
@@ -560,7 +561,7 @@ char *name;
 }
 
 PUBLIC void size_error(seg, count, size)
-char seg;
+int seg;
 offset_t count;
 offset_t size;
 {
diff --git a/ld/ld.c b/ld/ld.c
index c19b98d..a333f04 100644
--- a/ld/ld.c
+++ b/ld/ld.c
@@ -12,7 +12,6 @@ extern int errno;
 char *strcat P((char *dest, const char *src));
 unsigned long strtoul P((const char *s, char **endptr, int base));
 #else
-#undef NULL
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
@@ -22,23 +21,23 @@ unsigned long strtoul P((const char *s, char **endptr, int base));
 #define R_OK	0
 int access P((const char *path, int amode));
 #else
-#undef NULL
 #include <unistd.h>
 #endif
 
 #define MAX_LIBS	(NR_STDLIBS + 5)
+#ifdef MC6809
 #define NR_STDLIBS	1
+#else
+#define NR_STDLIBS	0
+#endif
 
 PUBLIC long text_base_address;	/* XXX */
+PUBLIC int doscomfile = 0;
 
 PRIVATE bool_t flag[128];
 PRIVATE char *libs[MAX_LIBS] = {
 #ifdef MC6809
     "/usr/local/lib/m09/",
-#else
-    /* One of the following values will be inserted at run time. */
-#   define std386lib	"/usr/local/lib/i386/"
-#   define std86lib	"/usr/local/lib/i86/"
 #endif
     0
 };
@@ -67,10 +66,6 @@ char *fn;
     char *path;
     int i;
 
-#ifndef MC6809
-    libs[0] = flag['3'] ? std386lib : std86lib;
-#endif
-
     for (i = lastlib - 1; i >= 0; --i)
     {
 	path = ourmalloc(strlen(libs[i]) + strlen(fn) + 1);
@@ -80,7 +75,7 @@ char *fn;
 	    return path;
 	ourfree(path);
     }
-    return NULL;
+    return NUL_PTR;
 }
 
 PUBLIC int main(argc, argv)
@@ -104,7 +99,7 @@ char **argv;
 #ifndef MC6809
     flag['z'] = flag['3'] = sizeof(char *) >= 4;
 #endif
-    outfilename = NULL;
+    outfilename = NUL_PTR;
     for (argn = 1; argn < argc; ++argn)
     {
 	arg = argv[argn];
@@ -133,9 +128,17 @@ char **argv;
 		if (arg[1] == '0')	/* flag 0 is negative logic flag 3 */
 		    flag['3'] = !flag['0'];
 		break;
+	    case 'd':		/* Make DOS com file */
+	        flag['3'] = FALSE;
+	        flag['z'] = FALSE;
+	        flag['0'] = TRUE;
+	        flag['s'] = TRUE;
+	        flag['d'] = TRUE;
+		text_base_address = 0x100;
+		break;
 	    case 'C':		/* startfile name */
 		tfn = buildname(crtprefix, arg + 2, crtsuffix);
-		if ((infilename = expandlib(tfn)) == NULL)
+		if ((infilename = expandlib(tfn)) == NUL_PTR)
 		    fatalerror(tfn);	/* XXX - need to describe failure */
 		readsyms(infilename, flag['t']);
 		break;
@@ -146,7 +149,7 @@ char **argv;
 		    fatalerror("too many library paths");
 		break;
 	    case 'O':		/* library file name */
-		if ((infilename = expandlib(arg + 2)) == NULL)
+		if ((infilename = expandlib(arg + 2)) == NUL_PTR)
 		    fatalerror(arg);	/* XXX */
 		readsyms(infilename, flag['t']);
 		break;
@@ -154,18 +157,18 @@ char **argv;
 		if (arg[2] != 0 || ++argn >= argc)
 		    usage();
 		errno = 0;    
-		text_base_address = strtoul(argv[argn], (char **) NULL, 16);
+		text_base_address = strtoul(argv[argn], (char **) NUL_PTR, 16);
 		if (errno != 0)
 		    use_error("invalid text address");
 		break;
 	    case 'l':		/* library name */
 		tfn = buildname(libprefix, arg + 2, libsuffix);
-		if ((infilename = expandlib(tfn)) == NULL)
+		if ((infilename = expandlib(tfn)) == NUL_PTR)
 		    fatalerror(tfn);	/* XXX */
 		readsyms(infilename, flag['t']);
 		break;
 	    case 'o':		/* output file name */
-		if (arg[2] != 0 || ++argn >= argc || outfilename != NULL)
+		if (arg[2] != 0 || ++argn >= argc || outfilename != NUL_PTR)
 		    usage();
 		outfilename = argv[argn];
 		break;
@@ -173,8 +176,9 @@ char **argv;
 		usage();
 	    }
     }
+    doscomfile = flag['d'];
     linksyms(flag['r']);
-    if (outfilename == NULL)
+    if (outfilename == NUL_PTR)
 	outfilename = "a.out";
     writebin(outfilename, flag['i'], flag['3'], flag['s'],
 	     flag['z'] & flag['3']);
diff --git a/ld/readobj.c b/ld/readobj.c
index 791436f..bb6a6b5 100644
--- a/ld/readobj.c
+++ b/ld/readobj.c
@@ -14,7 +14,6 @@ int strncmp P((const char *s1, const char *s2, unsigned n));
 char *strncpy P((char *dest, const char *src, unsigned n));
 unsigned long strtoul P((const char *s, char **endptr, int base));
 #else
-#undef NULL
 #include <stdlib.h>
 #include <string.h>
 #endif
@@ -51,9 +50,9 @@ FORWARD unsigned segbits P((unsigned seg, char *sizedesc));
 
 PUBLIC void objinit()
 {
-    modfirst = modlast = NULL;
-    entryfirst = entrylast = NULL;
-    redfirst = redlast = NULL;
+    modfirst = modlast = NUL_PTR;
+    entryfirst = entrylast = NUL_PTR;
+    redfirst = redlast = NUL_PTR;
 }
 
 /* read all symbol definitions in an object file */
@@ -76,7 +75,7 @@ bool_pt trace;
     case OMAGIC:
 	seekin((unsigned long) 0);
 	for (modcount = readfileheader(); modcount-- != 0;)
-	    readmodule(filename, (char *) NULL);
+	    readmodule(filename, (char *) NUL_PTR);
 	break;
     default:
 	seekin((unsigned long) 0);
@@ -118,7 +117,7 @@ char **parchentry;
     do
 	*endptr = 0;
     while (endptr > nameptr && *--endptr == ' ');
-    return strtoul(arheader.ar_size, (char **) NULL, 0);
+    return strtoul(arheader.ar_size, (char **) NUL_PTR, 0);
 }
 
 /* read and check file header of the object file just opened */
@@ -185,7 +184,7 @@ char *archentry;
     {
 	symname = readstring();
 	if ((flags = symdptr->dflags) & (E_MASK | I_MASK) &&
-	    (symptr = findsym(symname)) != NULL)
+	    (symptr = findsym(symname)) != NUL_PTR)
 	{
 	    /*
 	       weaken segment-checking by letting the maximum segment
@@ -220,7 +219,7 @@ char *archentry;
 	if (flags & N_MASK)
 	    entrysym(symptr);
     }
-    *symparray = NULL;
+    *symparray = NUL_PTR;
 }
 
 /* put symbol on entry symbol list if it is not already */
@@ -230,13 +229,13 @@ struct symstruct *symptr;
 {
     register struct entrylist *elptr;
 
-    for (elptr = entryfirst; elptr != NULL; elptr = elptr->elnext)
+    for (elptr = entryfirst; elptr != NUL_PTR; elptr = elptr->elnext)
 	if (symptr == elptr->elsymptr)
 	    return;
     elptr = (struct entrylist *) ourmalloc(sizeof(struct entrylist));
-    elptr->elnext = NULL;
+    elptr->elnext = NUL_PTR;
     elptr->elsymptr = symptr;
-    if (entryfirst == NULL)
+    if (entryfirst == NUL_PTR)
 	entryfirst = elptr;
     else
 	entrylast->elnext = elptr;
@@ -263,7 +262,7 @@ PRIVATE void reedmodheader()
 
     readin((char *) &modheader, sizeof modheader);
     modptr = (struct modstruct *) ourmalloc(sizeof(struct modstruct));
-    modptr->modnext = NULL;
+    modptr->modnext = NUL_PTR;
     modptr->textoffset = c4u4(modheader.htextoffset);
     modptr->class = modheader.hclass;
     readin(modptr->segmaxsize, sizeof modptr->segmaxsize);
@@ -281,7 +280,7 @@ PRIVATE void reedmodheader()
 	    cptr += count;
 	}
     }
-    if (modfirst == NULL)
+    if (modfirst == NUL_PTR)
 	modfirst = modptr;
     else
 	modlast->modnext = modptr;
@@ -298,11 +297,11 @@ offset_t value;
     if (symptr->modptr->class != (class = modlast->class))
 	for (rlptr = redfirst;; rlptr = rlptr->rlnext)
 	{
-	    if (rlptr == NULL)
+	    if (rlptr == NUL_PTR)
 	    {
 		rlptr = (struct redlist *)
 		    ourmalloc(sizeof(struct redlist));
-		rlptr->rlnext = NULL;
+		rlptr->rlnext = NUL_PTR;
 		rlptr->rlsymptr = symptr;
 		if (symptr->modptr->class < class)
 		    /* prefer lower class - put other on redlist */
@@ -317,7 +316,7 @@ offset_t value;
 		    rlptr->rlvalue = symptr->value;
 		    symptr->value = value;
 		}
-		if (redfirst == NULL)
+		if (redfirst == NUL_PTR)
 		    redfirst = rlptr;
 		else
 		    redlast->rlnext = rlptr;
diff --git a/ld/table.c b/ld/table.c
index 5260741..cbe4217 100644
--- a/ld/table.c
+++ b/ld/table.c
@@ -10,9 +10,10 @@
 
 #ifdef STDC_HEADERS_MISSING
 void *malloc P((unsigned size));
+char * strcpy P((char* dest, char* src));
 #else
-#undef NULL
 #include <stdlib.h>
+#include <string.h>
 #endif
 
 #define GOLDEN		157	/* GOLDEN/HASHTABSIZE approx golden ratio */
@@ -32,13 +33,13 @@ PUBLIC void syminit()
 
     for (i = sizeof(int) <= 2 ? 0xE000 : (unsigned) 0x38000;
 	 i != 0; i -= 512)
-	if ((tableptr = malloc(i)) != NULL)
+	if ((tableptr = malloc(i)) != NUL_PTR)
 	    break;
-    if (tableptr == NULL)
+    if (tableptr == NUL_PTR)
 	outofmemory();
     tableend = tableptr + i;
     for (i = 0; i < HASHTABSIZE; i++)
-	hashtab[i] = NULL;
+	hashtab[i] = NUL_PTR;
 }
 
 /* add named symbol to end of table - initialise only name and next fields */
@@ -48,12 +49,12 @@ PUBLIC struct symstruct *addsym(name)
 char *name;
 {
     struct symstruct **hashptr;
-    struct symstruct *oldsymptr;
+    struct symstruct *oldsymptr = 0;
     struct symstruct *symptr;
 
     hashptr = gethashptr(name);
     symptr = *hashptr;
-    while (symptr != NULL)
+    while (symptr != NUL_PTR)
     {
 	oldsymptr = symptr;
 	symptr = symptr->next;
@@ -62,11 +63,11 @@ char *name;
     symptr = (struct symstruct *) tableptr;
     if ((tableptr = symptr->name + (strlen(name) + 1)) > tableend)
 	outofmemory();
-    symptr->modptr = NULL;
-    symptr->next = NULL;
+    symptr->modptr = NUL_PTR;
+    symptr->next = NUL_PTR;
     if (name != symptr->name)
 	strcpy(symptr->name, name);	/* should't happen */
-    if (*hashptr == NULL)
+    if (*hashptr == NUL_PTR)
 	*hashptr = symptr;
     else
 	oldsymptr->next = symptr;
@@ -81,7 +82,7 @@ char *name;
     struct symstruct *symptr;
 
     symptr = *gethashptr(name);
-    while (symptr != NULL && (!(symptr->flags & (E_MASK | I_MASK)) ||
+    while (symptr != NUL_PTR && (!(symptr->flags & (E_MASK | I_MASK)) ||
 			      strcmp(symptr->name, name) != 0))
 	symptr = symptr->next;
     return symptr;
diff --git a/ld/writebin.c b/ld/writebin.c
index a95280c..3e7602d 100644
--- a/ld/writebin.c
+++ b/ld/writebin.c
@@ -27,7 +27,11 @@ static long bdataoffset;
 #  define n_was_strx n_un.n_strx
 #  define n_was_type n_desc
 # else /* not BSD_A_OUT */
-#  include "a.out.h"		/* maybe local copy of <a.out.h> for X-link */
+#  ifdef MSDOS
+#   include "a_out.h"
+#  else
+#   include "a.out.h"		/* maybe local copy of <a.out.h> for X-link */
+#  endif
 #  define n_was_name n_name
 #  define n_was_numaux n_numaux
 #  define n_was_other n_other
@@ -46,7 +50,6 @@ static long bdataoffset;
 #ifdef STDC_HEADERS_MISSING
 void *memset P((void *s, int c, unsigned n));
 #else
-#undef NULL
 #include <string.h>
 #endif
 
@@ -58,10 +61,10 @@ void *memset P((void *s, int c, unsigned n));
 #  ifdef STANDARD_GNU_A_OUT
 #   define FILEHEADERLENGTH 32
 #  else
-#   define FILEHEADERLENGTH 48
+#   define FILEHEADERLENGTH (doscomfile?0:48)
 #  endif
 # else
-#  define FILEHEADERLENGTH A_MINHDR
+#  define FILEHEADERLENGTH (doscomfile?0:A_MINHDR)
 				/* part of header not counted in offsets */
 # endif
 #endif
@@ -139,6 +142,8 @@ FORWARD void writeheader P((void));
 #endif
 FORWARD void writenulls P((offset_t count));
 
+extern int doscomfile;
+
 /* link all symbols connected to entry symbols */
 
 PUBLIC void linksyms(argreloc_output)
@@ -153,31 +158,31 @@ bool_pt argreloc_output;
     reloc_output = argreloc_output;
     if (argreloc_output)
     {
-	if (modfirst->modnext != NULL)
+	if (modfirst->modnext != NUL_PTR)
 	    fatalerror("relocatable output only works for one input file");
-	for (modptr = modfirst; modptr != NULL; modptr = modptr->modnext)
+	for (modptr = modfirst; modptr != NUL_PTR; modptr = modptr->modnext)
 	    modptr->loadflag = TRUE;
 	return;
     }
 #endif
-    if ((symptr = findsym("_main")) != NULL)
+    if ((symptr = findsym("_main")) != NUL_PTR)
 	entrysym(symptr);
     do
     {
-	if ((elptr = entryfirst) == NULL)
+	if ((elptr = entryfirst) == NUL_PTR)
 	    fatalerror("no start symbol");
-	for (modptr = modfirst; modptr != NULL; modptr = modptr->modnext)
+	for (modptr = modfirst; modptr != NUL_PTR; modptr = modptr->modnext)
 	    modptr->loadflag = FALSE;
-	for (; elptr != NULL; elptr = elptr->elnext)
+	for (; elptr != NUL_PTR; elptr = elptr->elnext)
 	    linkrefs(elptr->elsymptr->modptr);
-	if ((symptr = findsym("start")) != NULL)
+	if ((symptr = findsym("start")) != NUL_PTR)
 	    linkrefs(symptr->modptr);
 	needlink = FALSE;
 	{
-	    struct redlist *prlptr;
+	    struct redlist *prlptr = 0;
 	    struct redlist *rlptr;
 
-	    for (rlptr = redfirst; rlptr != NULL;
+	    for (rlptr = redfirst; rlptr != NUL_PTR;
 		 rlptr = (prlptr = rlptr)->rlnext)
 		if (rlptr->rlmodptr->loadflag &&
 		    rlptr->rlmodptr->class > rlptr->rlsymptr->modptr->class)
@@ -233,9 +238,9 @@ bool_pt arguzp;
     }
 #ifdef EDOS
     commandname = stralloc(outfilename);
-    if ((cptr = strchr(commandname, ':')) != NULL)
+    if ((cptr = strchr(commandname, ':')) != NUL_PTR)
 	commandname = cptr + 1;
-    if ((cptr = strrchr(commandname, '.')) != NULL)
+    if ((cptr = strrchr(commandname, '.')) != NUL_PTR)
 	*cptr = 0;
 #endif
 
@@ -261,18 +266,19 @@ bool_pt arguzp;
     symres("__end");
     curseg = 0;			/* text seg, s.b. variable */
     symres("__etext");
+    symres("__segoff");
 
     /* calculate segment and common sizes (sum over loaded modules) */
     /* use zero init of segsz[] */
     /* also relocate symbols relative to starts of their segments */
-    for (modptr = modfirst; modptr != NULL; modptr = modptr->modnext)
+    for (modptr = modfirst; modptr != NUL_PTR; modptr = modptr->modnext)
 	if (modptr->loadflag)
 	{
 	    register struct symstruct **symparray;
 	    register struct symstruct *symptr;
 
 	    for (symparray = modptr->symparray;
-		 (symptr = *symparray) != NULL; ++symparray)
+		 (symptr = *symparray) != NUL_PTR; ++symparray)
 		if (symptr->modptr == modptr && !(symptr->flags & A_MASK))
 		{
 		    if (!(symptr->flags & (I_MASK | SA_MASK)))
@@ -363,14 +369,14 @@ bool_pt arguzp;
     }
 
     /* relocate symbols by offsets of segments in memory */
-    for (modptr = modfirst; modptr != NULL; modptr = modptr->modnext)
+    for (modptr = modfirst; modptr != NUL_PTR; modptr = modptr->modnext)
 	if (modptr->loadflag)
 	{
 	    register struct symstruct **symparray;
 	    register struct symstruct *symptr;
 
 	    for (symparray = modptr->symparray;
-		 (symptr = *symparray) != NULL; ++symparray)
+		 (symptr = *symparray) != NUL_PTR; ++symparray)
 		if (symptr->modptr == modptr && !(symptr->flags & A_MASK))
 		{
 		    if (symptr->flags & (C_MASK | SA_MASK))
@@ -414,6 +420,7 @@ bool_pt arguzp;
     setsym("__etext", etextoffset);
     setsym("__edata", edataoffset);
     setsym("__end", endoffset = combase[NSEG - 1] + comsz[NSEG - 1]);
+    setsym("__segoff", (offset_t)(segadj[1]-segadj[0])/0x10);
 
     openout(outfilename);
 #ifdef BSD_A_OUT
@@ -427,7 +434,7 @@ bool_pt arguzp;
 #else
     writeheader();
 #endif
-    for (modptr = modfirst; modptr != NULL; modptr = modptr->modnext)
+    for (modptr = modfirst; modptr != NUL_PTR; modptr = modptr->modnext)
 	if (modptr->loadflag)
 	{
 	    linkmod(modptr);
@@ -453,21 +460,21 @@ bool_pt arguzp;
 #ifdef BSD_A_OUT
 	stringoff = 4;
 #endif
-	for (modptr = modfirst; modptr != NULL; modptr = modptr->modnext)
+	for (modptr = modfirst; modptr != NUL_PTR; modptr = modptr->modnext)
 	    if (modptr->loadflag)
 	    {
 		register struct symstruct **symparray;
 		register struct symstruct *symptr;
 
 		for (symparray = modptr->symparray;
-		     (symptr = *symparray) != NULL; ++symparray)
+		     (symptr = *symparray) != NUL_PTR; ++symparray)
 		    if (symptr->modptr == modptr)
 		    {
 #ifdef BSD_A_OUT
 			offtocn((char *) &extsym.n_was_strx,
 				(offset_t) stringoff, 4);
 #else
-			strncpy((char *) &extsym.n_was_name, symptr->name,
+			strncpy((char *) extsym.n_was_name, symptr->name,
 				sizeof extsym.n_was_name);
 #endif
 			u4cn((char *) &extsym.n_value, (u4_t) symptr->value,
@@ -506,14 +513,14 @@ bool_pt arguzp;
 #ifdef BSD_A_OUT
 	offtocn((char *) &extsym.n_was_strx, (offset_t) stringoff, 4);
 	writeout((char *) &extsym.n_was_strx, 4);
-	for (modptr = modfirst; modptr != NULL; modptr = modptr->modnext)
+	for (modptr = modfirst; modptr != NUL_PTR; modptr = modptr->modnext)
 	    if (modptr->loadflag)
 	    {
 		register struct symstruct **symparray;
 		register struct symstruct *symptr;
 
 		for (symparray = modptr->symparray;
-		     (symptr = *symparray) != NULL; ++symparray)
+		     (symptr = *symparray) != NUL_PTR; ++symparray)
 		    if (symptr->modptr == modptr)
 			writeout(symptr->name, strlen(symptr->name) + 1);
 	    }
@@ -553,12 +560,12 @@ char *commandname;
 
     count = 2 + 2 + 1;		/* len len nul */
     startptr = findsym("start");
-    for (elptr = entryfirst; elptr != NULL; elptr = elptr->elnext)
+    for (elptr = entryfirst; elptr != NUL_PTR; elptr = elptr->elnext)
     {
 	name = idconvert(elptr, commandname);
 	count += strlen(name) + 1 + 2 + 1;	/* nul off flg */
 	ourfree(name);
-	if (startptr != NULL)
+	if (startptr != NUL_PTR)
 	    count += 6;		/* LBSR $xxxx and LBRA $xxxx */
     }
     return count;
@@ -772,7 +779,7 @@ struct modstruct *modptr;
 
     modptr->loadflag = TRUE;
     for (symparray = modptr->symparray;
-	 (symptr = *symparray) != NULL; ++symparray)
+	 (symptr = *symparray) != NUL_PTR; ++symparray)
 	if (symptr->modptr->loadflag == FALSE)
 	    linkrefs(symptr->modptr);
 }
@@ -815,7 +822,7 @@ offset_t value;
 #ifdef BSD_A_OUT
     if (!reloc_output)
 #endif
-	if ((symptr = findsym(name)) != NULL)
+	if ((symptr = findsym(name)) != NUL_PTR)
 	    symptr->value = value;
 }
 
@@ -824,7 +831,7 @@ register char *name;
 {
     register struct symstruct *symptr;
 
-    if ((symptr = findsym(name)) != NULL)
+    if ((symptr = findsym(name)) != NUL_PTR)
     {
 	if ((symptr->flags & SEGM_MASK) == SEGM_MASK)
 	    symptr->flags &= ~SEGM_MASK | curseg;
@@ -870,7 +877,7 @@ char *commandname;
     struct symstruct *startptr;
 
     headlength = binheaderlength(commandname);
-    for (elptr = entryfirst; elptr != NULL; elptr = elptr->elnext)
+    for (elptr = entryfirst; elptr != NUL_PTR; elptr = elptr->elnext)
 	headlength -= 6;
     offset = headlength;
     startptr = findsym("start");
@@ -878,21 +885,21 @@ char *commandname;
     writeout(buf, 2);
     writechar(0xFF);		/* dummy data length 0xFFFF takes everything */
     writechar(0xFF);
-    for (elptr = entryfirst; elptr != NULL; elptr = elptr->elnext)
+    for (elptr = entryfirst; elptr != NUL_PTR; elptr = elptr->elnext)
     {
 	name = idconvert(elptr, commandname);
 	writeout(name, (unsigned) strlen(name) + 1);
 	ourfree(name);
-	offtocn(buf, startptr == NULL ? elptr->elsymptr->value : offset, 2);
+	offtocn(buf, startptr == NUL_PTR ? elptr->elsymptr->value : offset, 2);
 	writeout(buf, 2);
 	writechar(0x82);	/* 8 = set flags from here, 2 = cmd line */
 	offset += 6;		/* LBSR $xxxx and LBRA $xxxx */
     }
     writechar(0);
-    if (startptr != NULL)
+    if (startptr != NUL_PTR)
     {
 	offset = headlength + 3;	/* over 1st LBSR */
-	for (elptr = entryfirst; elptr != NULL; elptr = elptr->elnext)
+	for (elptr = entryfirst; elptr != NUL_PTR; elptr = elptr->elnext)
 	{
 	    writechar(0x17);	/* LBSR */
 	    offtocn(buf, startptr->value - offset, 2);
@@ -975,7 +982,8 @@ PRIVATE void writeheader()
 		sizeof header.a_total);
 #endif
     }
-    writeout((char *) &header, FILEHEADERLENGTH);
+    if( FILEHEADERLENGTH )
+       writeout((char *) &header, FILEHEADERLENGTH);
 }
 
 #endif /* MINIX */