liblink: create new library based on linker code

There is an enormous amount of code moving around in this CL,
but the code is the same, and it is invoked in the same ways.
This CL is preparation for the new linker structure, not the new
structure itself.

The new library's definition is in include/link.h.

The main change is the use of a Link structure to hold all the
linker-relevant state, replacing the smattering of global variables.
The Link structure should both make it clearer which state must
be carried around and make it possible to parallelize more easily
later.

The main body of the linker has moved into the architecture-independent
cmd/ld directory. That includes the list of known header types, so the
distinction between Hplan9x32 and Hplan9x64 is removed (no other
header type distinguished 32- and 64-bit formats), and code for unused
formats such as ipaq kernels has been deleted.

The code being deleted from 5l, 6l, and 8l reappears in liblink or in ld.
Because multiple files are being merged in the liblink directory,
it is not possible to show the diffs nicely in hg.

The Prog and Addr structures have been unified into an
architecture-independent form and moved to link.h, where they will
be shared by all tools: the assemblers, the compilers, and the linkers.
The unification makes it possible to write architecture-independent
traversal of Prog lists, among other benefits.

The Sym structures cannot be unified: they are too fundamentally
different between the linker and the compilers. Instead, liblink defines
an LSym - a linker Sym - to be used in the Prog and Addr structures,
and the linker now refers exclusively to LSyms. The compilers will
keep using their own syms but will fill out the corresponding LSyms in
the Prog and Addr structures.

Although code from 5l, 6l, and 8l is now in a single library, the
code has been arranged so that only one architecture needs to
be linked into a particular program: 5l will not contain the code
needed for x86 instruction layout, for example.

The object file writing code in liblink/obj.c is from cmd/gc/obj.c.

Preparation for golang.org/s/go13linker work.

This CL does not build by itself. It depends on 35740044
and will be submitted at the same time.

R=iant
CC=golang-dev
https://codereview.appspot.com/35790044

1 files changed, 114 insertions, 1192 deletions

diff --git a/src/cmd/ld/lib.c b/src/cmd/ld/lib.c
index da522dc0c..56e50acb9 100644
--- a/src/cmd/ld/lib.c
+++ b/src/cmd/ld/lib.c
@@ -32,6 +32,7 @@
 #include	"l.h"
 #include	"lib.h"
 #include	"../ld/elf.h"
+#include	"../ld/dwarf.h"
 #include	"../../pkg/runtime/stack.h"
 #include	"../../pkg/runtime/funcdata.h"
 
@@ -48,18 +49,9 @@ int iconv(Fmt*);
 
 char	symname[]	= SYMDEF;
 char	pkgname[]	= "__.PKGDEF";
-char**	libdir;
-int	nlibdir = 0;
-static int	maxlibdir = 0;
 static int	cout = -1;
 
-// symbol version, incremented each time a file is loaded.
-// version==1 is reserved for savehist.
-enum
-{
-	HistVersion = 1,
-};
-int	version = HistVersion;
+extern int	version;
 
 // Set if we see an object compiled by the host compiler that is not
 // from a package that is known to support internal linking mode.
@@ -77,15 +69,15 @@ Lflag(char *arg)
 {
 	char **p;
 
-	if(nlibdir >= maxlibdir) {
-		if (maxlibdir == 0)
-			maxlibdir = 8;
+	if(ctxt->nlibdir >= ctxt->maxlibdir) {
+		if (ctxt->maxlibdir == 0)
+			ctxt->maxlibdir = 8;
 		else
-			maxlibdir *= 2;
-		p = erealloc(libdir, maxlibdir * sizeof(*p));
-		libdir = p;
+			ctxt->maxlibdir *= 2;
+		p = erealloc(ctxt->libdir, ctxt->maxlibdir * sizeof(*p));
+		ctxt->libdir = p;
 	}
-	libdir[nlibdir++] = arg;
+	ctxt->libdir[ctxt->nlibdir++] = arg;
 }
 
 void
@@ -132,7 +124,7 @@ libinit(void)
 			sprint(INITENTRY, "_rt0_%s_%s_lib", goarch, goos);
 		}
 	}
-	lookup(INITENTRY, 0)->type = SXREF;
+	linklookup(ctxt, INITENTRY, 0)->type = SXREF;
 }
 
 void
@@ -147,158 +139,18 @@ errorexit(void)
 }
 
 void
-addlib(char *src, char *obj)
-{
-	char name[1024], pname[1024], comp[256], *p;
-	int i, search;
-
-	if(histfrogp <= 0)
-		return;
-
-	search = 0;
-	if(histfrog[0]->name[1] == '/') {
-		sprint(name, "");
-		i = 1;
-	} else
-	if(isalpha((uchar)histfrog[0]->name[1]) && histfrog[0]->name[2] == ':') {
-		strcpy(name, histfrog[0]->name+1);
-		i = 1;
-	} else
-	if(histfrog[0]->name[1] == '.') {
-		sprint(name, ".");
-		i = 0;
-	} else {
-		sprint(name, "");
-		i = 0;
-		search = 1;
-	}
-
-	for(; i<histfrogp; i++) {
-		snprint(comp, sizeof comp, "%s", histfrog[i]->name+1);
-		for(;;) {
-			p = strstr(comp, "$O");
-			if(p == 0)
-				break;
-			memmove(p+1, p+2, strlen(p+2)+1);
-			p[0] = thechar;
-		}
-		for(;;) {
-			p = strstr(comp, "$M");
-			if(p == 0)
-				break;
-			if(strlen(comp)+strlen(thestring)-2+1 >= sizeof comp) {
-				diag("library component too long");
-				return;
-			}
-			memmove(p+strlen(thestring), p+2, strlen(p+2)+1);
-			memmove(p, thestring, strlen(thestring));
-		}
-		if(strlen(name) + strlen(comp) + 3 >= sizeof(name)) {
-			diag("library component too long");
-			return;
-		}
-		if(i > 0 || !search)
-			strcat(name, "/");
-		strcat(name, comp);
-	}
-	cleanname(name);
-	
-	// runtime.a -> runtime
-	p = nil;
-	if(strlen(name) > 2 && name[strlen(name)-2] == '.') {
-		p = name+strlen(name)-2;
-		*p = '\0';
-	}
-	
-	// already loaded?
-	for(i=0; i<libraryp; i++)
-		if(strcmp(library[i].pkg, name) == 0)
-			return;
-	
-	// runtime -> runtime.a for search
-	if(p != nil)
-		*p = '.';
-
-	if(search) {
-		// try dot, -L "libdir", and then goroot.
-		for(i=0; i<nlibdir; i++) {
-			snprint(pname, sizeof pname, "%s/%s", libdir[i], name);
-			if(access(pname, AEXIST) >= 0)
-				break;
-		}
-	}else
-		strcpy(pname, name);
-	cleanname(pname);
-
-	/* runtime.a -> runtime */
-	if(p != nil)
-		*p = '\0';
-
-	if(debug['v'] > 1)
-		Bprint(&bso, "%5.2f addlib: %s %s pulls in %s\n", cputime(), obj, src, pname);
-
-	addlibpath(src, obj, pname, name);
-}
-
-/*
- * add library to library list.
- *	srcref: src file referring to package
- *	objref: object file referring to package
- *	file: object file, e.g., /home/rsc/go/pkg/container/vector.a
- *	pkg: package import path, e.g. container/vector
- */
-void
-addlibpath(char *srcref, char *objref, char *file, char *pkg)
-{
-	int i;
-	Library *l;
-	char *p;
-
-	for(i=0; i<libraryp; i++)
-		if(strcmp(file, library[i].file) == 0)
-			return;
-
-	if(debug['v'] > 1)
-		Bprint(&bso, "%5.2f addlibpath: srcref: %s objref: %s file: %s pkg: %s\n",
-			cputime(), srcref, objref, file, pkg);
-
-	if(libraryp == nlibrary){
-		nlibrary = 50 + 2*libraryp;
-		library = erealloc(library, sizeof library[0] * nlibrary);
-	}
-
-	l = &library[libraryp++];
-
-	p = mal(strlen(objref) + 1);
-	strcpy(p, objref);
-	l->objref = p;
-
-	p = mal(strlen(srcref) + 1);
-	strcpy(p, srcref);
-	l->srcref = p;
-
-	p = mal(strlen(file) + 1);
-	strcpy(p, file);
-	l->file = p;
-
-	p = mal(strlen(pkg) + 1);
-	strcpy(p, pkg);
-	l->pkg = p;
-}
-
-void
 loadinternal(char *name)
 {
 	char pname[1024];
 	int i, found;
 
 	found = 0;
-	for(i=0; i<nlibdir; i++) {
-		snprint(pname, sizeof pname, "%s/%s.a", libdir[i], name);
+	for(i=0; i<ctxt->nlibdir; i++) {
+		snprint(pname, sizeof pname, "%s/%s.a", ctxt->libdir[i], name);
 		if(debug['v'])
 			Bprint(&bso, "searching for %s.a in %s\n", name, pname);
 		if(access(pname, AEXIST) >= 0) {
-			addlibpath("internal", "internal", pname, name);
+			addlibpath(ctxt, "internal", "internal", pname, name);
 			found = 1;
 			break;
 		}
@@ -311,12 +163,12 @@ void
 loadlib(void)
 {
 	int i, w, x;
-	Sym *s, *gmsym;
+	LSym *s, *gmsym;
 
 	if(flag_shared) {
-		s = lookup("runtime.islibrary", 0);
+		s = linklookup(ctxt, "runtime.islibrary", 0);
 		s->dupok = 1;
-		adduint8(s, 1);
+		adduint8(ctxt, s, 1);
 	}
 
 	loadinternal("runtime");
@@ -332,17 +184,17 @@ loadlib(void)
 		loadinternal("runtime/cgo");
 		// Pretend that we really imported the package.
 		// This will do no harm if we did in fact import it.
-		s = lookup("go.importpath.runtime/cgo.", 0);
+		s = linklookup(ctxt, "go.importpath.runtime/cgo.", 0);
 		s->type = SDATA;
 		s->dupok = 1;
 		s->reachable = 1;
 	}
 
-	for(i=0; i<libraryp; i++) {
+	for(i=0; i<ctxt->libraryp; i++) {
 		if(debug['v'] > 1)
-			Bprint(&bso, "%5.2f autolib: %s (from %s)\n", cputime(), library[i].file, library[i].objref);
-		iscgo |= strcmp(library[i].pkg, "runtime/cgo") == 0;
-		objfile(library[i].file, library[i].pkg);
+			Bprint(&bso, "%5.2f autolib: %s (from %s)\n", cputime(), ctxt->library[i].file, ctxt->library[i].objref);
+		iscgo |= strcmp(ctxt->library[i].pkg, "runtime/cgo") == 0;
+		objfile(ctxt->library[i].file, ctxt->library[i].pkg);
 	}
 	
 	if(linkmode == LinkAuto) {
@@ -355,7 +207,7 @@ loadlib(void)
 	if(linkmode == LinkInternal) {
 		// Drop all the cgo_import_static declarations.
 		// Turns out we won't be needing them.
-		for(s = allsym; s != S; s = s->allsym)
+		for(s = ctxt->allsym; s != S; s = s->allsym)
 			if(s->type == SHOSTOBJ) {
 				// If a symbol was marked both
 				// cgo_import_static and cgo_import_dynamic,
@@ -368,7 +220,7 @@ loadlib(void)
 			}
 	}
 	
-	gmsym = lookup("runtime.tlsgm", 0);
+	gmsym = linklookup(ctxt, "runtime.tlsgm", 0);
 	gmsym->type = STLSBSS;
 	gmsym->size = 2*PtrSize;
 	gmsym->hide = 1;
@@ -539,7 +391,7 @@ dowrite(int fd, char *p, int n)
 	while(n > 0) {
 		m = write(fd, p, n);
 		if(m <= 0) {
-			cursym = S;
+			ctxt->cursym = S;
 			diag("write error: %r");
 			errorexit();
 		}
@@ -628,7 +480,7 @@ hostobjs(void)
 		h = &hostobj[i];
 		f = Bopen(h->file, OREAD);
 		if(f == nil) {
-			cursym = S;
+			ctxt->cursym = S;
 			diag("cannot reopen %s: %r", h->pn);
 			errorexit();
 		}
@@ -744,7 +596,7 @@ hostlink(void)
 		h = &hostobj[i];
 		f = Bopen(h->file, OREAD);
 		if(f == nil) {
-			cursym = S;
+			ctxt->cursym = S;
 			diag("cannot reopen %s: %r", h->pn);
 			errorexit();
 		}
@@ -753,7 +605,7 @@ hostlink(void)
 		argv[argc++] = p;
 		w = create(p, 1, 0775);
 		if(w < 0) {
-			cursym = S;
+			ctxt->cursym = S;
 			diag("cannot create %s: %r", p);
 			errorexit();
 		}
@@ -765,7 +617,7 @@ hostlink(void)
 			len -= n;
 		}
 		if(close(w) < 0) {
-			cursym = S;
+			ctxt->cursym = S;
 			diag("cannot write %s: %r", p);
 			errorexit();
 		}
@@ -798,7 +650,7 @@ hostlink(void)
 	}
 
 	if(runcmd(argv) < 0) {
-		cursym = S;
+		ctxt->cursym = S;
 		diag("%s: running %s failed: %r", argv0, argv[0]);
 		errorexit();
 	}
@@ -913,7 +765,7 @@ ldobj(Biobuf *f, char *pkg, int64 len, char *pn, char *file, int whence)
 	ldpkg(f, pkg, import1 - import0 - 2, pn, whence);	// -2 for !\n
 	Bseek(f, import1, 0);
 
-	ldobj1(f, pkg, eof - Boffset(f), pn);
+	ctxt->arch->ldobj(ctxt, f, pkg, eof - Boffset(f), pn);
 	free(pn);
 	return;
 
@@ -922,318 +774,12 @@ eof:
 	free(pn);
 }
 
-Sym*
-newsym(char *symb, int v)
-{
-	Sym *s;
-	int l;
-
-	l = strlen(symb) + 1;
-	s = mal(sizeof(*s));
-	if(debug['v'] > 1)
-		Bprint(&bso, "newsym %s\n", symb);
-
-	s->dynid = -1;
-	s->plt = -1;
-	s->got = -1;
-	s->name = mal(l + 1);
-	memmove(s->name, symb, l);
-
-	s->type = 0;
-	s->version = v;
-	s->value = 0;
-	s->sig = 0;
-	s->size = 0;
-	nsymbol++;
-
-	s->allsym = allsym;
-	allsym = s;
-
-	return s;
-}
-
-static Sym*
-_lookup(char *symb, int v, int creat)
-{
-	Sym *s;
-	char *p;
-	uint32 h;
-	int c;
-
-	h = v;
-	for(p=symb; c = *p; p++)
-		h = h+h+h + c;
-	// not if(h < 0) h = ~h, because gcc 4.3 -O2 miscompiles it.
-	h &= 0xffffff;
-	h %= NHASH;
-	for(s = hash[h]; s != S; s = s->hash)
-		if(strcmp(s->name, symb) == 0)
-			return s;
-	if(!creat)
-		return nil;
-
-	s = newsym(symb, v);
-	s->extname = s->name;
-	s->hash = hash[h];
-	hash[h] = s;
-
-	return s;
-}
-
-Sym*
-lookup(char *name, int v)
-{
-	return _lookup(name, v, 1);
-}
-
-// read-only lookup
-Sym*
-rlookup(char *name, int v)
-{
-	return _lookup(name, v, 0);
-}
-
-void
-copyhistfrog(char *buf, int nbuf)
-{
-	char *p, *ep;
-	int i;
-
-	p = buf;
-	ep = buf + nbuf;
-	for(i=0; i<histfrogp; i++) {
-		p = seprint(p, ep, "%s", histfrog[i]->name+1);
-		if(i+1<histfrogp && (p == buf || p[-1] != '/'))
-			p = seprint(p, ep, "/");
-	}
-}
-
-void
-addhist(int32 line, int type)
-{
-	Auto *u;
-	Sym *s;
-	int i, j, k;
-
-	u = mal(sizeof(Auto));
-	s = mal(sizeof(Sym));
-	s->name = mal(2*(histfrogp+1) + 1);
-
-	u->asym = s;
-	u->type = type;
-	u->aoffset = line;
-	u->link = curhist;
-	curhist = u;
-
-	s->name[0] = 0;
-	j = 1;
-	for(i=0; i<histfrogp; i++) {
-		k = histfrog[i]->value;
-		s->name[j+0] = k>>8;
-		s->name[j+1] = k;
-		j += 2;
-	}
-	s->name[j] = 0;
-	s->name[j+1] = 0;
-}
-
-void
-histtoauto(void)
-{
-	Auto *l;
-
-	while(l = curhist) {
-		curhist = l->link;
-		l->link = curauto;
-		curauto = l;
-	}
-}
-
-void
-collapsefrog(Sym *s)
-{
-	int i;
-
-	/*
-	 * bad encoding of path components only allows
-	 * MAXHIST components. if there is an overflow,
-	 * first try to collapse xxx/..
-	 */
-	for(i=1; i<histfrogp; i++)
-		if(strcmp(histfrog[i]->name+1, "..") == 0) {
-			memmove(histfrog+i-1, histfrog+i+1,
-				(histfrogp-i-1)*sizeof(histfrog[0]));
-			histfrogp--;
-			goto out;
-		}
-
-	/*
-	 * next try to collapse .
-	 */
-	for(i=0; i<histfrogp; i++)
-		if(strcmp(histfrog[i]->name+1, ".") == 0) {
-			memmove(histfrog+i, histfrog+i+1,
-				(histfrogp-i-1)*sizeof(histfrog[0]));
-			goto out;
-		}
-
-	/*
-	 * last chance, just truncate from front
-	 */
-	memmove(histfrog+0, histfrog+1,
-		(histfrogp-1)*sizeof(histfrog[0]));
-
-out:
-	histfrog[histfrogp-1] = s;
-}
-
-void
-nuxiinit(void)
-{
-	int i, c;
-
-	for(i=0; i<4; i++) {
-		c = find1(0x04030201L, i+1);
-		if(i < 2)
-			inuxi2[i] = c;
-		if(i < 1)
-			inuxi1[i] = c;
-		inuxi4[i] = c;
-		if(c == i) {
-			inuxi8[i] = c;
-			inuxi8[i+4] = c+4;
-		} else {
-			inuxi8[i] = c+4;
-			inuxi8[i+4] = c;
-		}
-		fnuxi4[i] = c;
-		fnuxi8[i] = c;
-		fnuxi8[i+4] = c+4;
-	}
-	if(debug['v']) {
-		Bprint(&bso, "inuxi = ");
-		for(i=0; i<1; i++)
-			Bprint(&bso, "%d", inuxi1[i]);
-		Bprint(&bso, " ");
-		for(i=0; i<2; i++)
-			Bprint(&bso, "%d", inuxi2[i]);
-		Bprint(&bso, " ");
-		for(i=0; i<4; i++)
-			Bprint(&bso, "%d", inuxi4[i]);
-		Bprint(&bso, " ");
-		for(i=0; i<8; i++)
-			Bprint(&bso, "%d", inuxi8[i]);
-		Bprint(&bso, "\nfnuxi = ");
-		for(i=0; i<4; i++)
-			Bprint(&bso, "%d", fnuxi4[i]);
-		Bprint(&bso, " ");
-		for(i=0; i<8; i++)
-			Bprint(&bso, "%d", fnuxi8[i]);
-		Bprint(&bso, "\n");
-	}
-	Bflush(&bso);
-}
-
-int
-find1(int32 l, int c)
-{
-	char *p;
-	int i;
-
-	p = (char*)&l;
-	for(i=0; i<4; i++)
-		if(*p++ == c)
-			return i;
-	return 0;
-}
-
-int
-find2(int32 l, int c)
-{
-	union {
-		int32 l;
-		short p[2];
-	} u;
-	short *p;
-	int i;
-
-	u.l = l;
-	p = u.p;
-	for(i=0; i<4; i+=2) {
-		if(((*p >> 8) & 0xff) == c)
-			return i;
-		if((*p++ & 0xff) == c)
-			return i+1;
-	}
-	return 0;
-}
-
-int32
-ieeedtof(Ieee *e)
-{
-	int exp;
-	int32 v;
-
-	if(e->h == 0)
-		return 0;
-	exp = (e->h>>20) & ((1L<<11)-1L);
-	exp -= (1L<<10) - 2L;
-	v = (e->h & 0xfffffL) << 3;
-	v |= (e->l >> 29) & 0x7L;
-	if((e->l >> 28) & 1) {
-		v++;
-		if(v & 0x800000L) {
-			v = (v & 0x7fffffL) >> 1;
-			exp++;
-		}
-	}
-	if(-148 <= exp && exp <= -126) {
-		v |= 1<<23;
-		v >>= -125 - exp;
-		exp = -126;
-	}
-	else if(exp < -148 || exp >= 130)
-		diag("double fp to single fp overflow: %.17g", ieeedtod(e));
-	v |= ((exp + 126) & 0xffL) << 23;
-	v |= e->h & 0x80000000L;
-	return v;
-}
-
-double
-ieeedtod(Ieee *ieeep)
-{
-	Ieee e;
-	double fr;
-	int exp;
-
-	if(ieeep->h & (1L<<31)) {
-		e.h = ieeep->h & ~(1L<<31);
-		e.l = ieeep->l;
-		return -ieeedtod(&e);
-	}
-	if(ieeep->l == 0 && ieeep->h == 0)
-		return 0;
-	exp = (ieeep->h>>20) & ((1L<<11)-1L);
-	exp -= (1L<<10) - 2L;
-	fr = ieeep->l & ((1L<<16)-1L);
-	fr /= 1L<<16;
-	fr += (ieeep->l>>16) & ((1L<<16)-1L);
-	fr /= 1L<<16;
-	if(exp == -(1L<<10) - 2L) {
-		fr += (ieeep->h & (1L<<20)-1L);
-		exp++;
-	} else
-		fr += (ieeep->h & (1L<<20)-1L) | (1L<<20);
-	fr /= 1L<<21;
-	return ldexp(fr, exp);
-}
-
 void
 zerosig(char *sp)
 {
-	Sym *s;
+	LSym *s;
 
-	s = lookup(sp, 0);
+	s = linklookup(ctxt, sp, 0);
 	s->sig = 0;
 }
 
@@ -1357,13 +903,6 @@ iconv(Fmt *fp)
 	return 0;
 }
 
-void
-mangle(char *file)
-{
-	fprint(2, "%s: mangled input file\n", file);
-	errorexit();
-}
-
 Section*
 addsection(Segment *seg, char *name, int rwx)
 {
@@ -1381,235 +920,6 @@ addsection(Segment *seg, char *name, int rwx)
 	return sect;
 }
 
-void
-addvarint(Sym *s, uint32 val)
-{
-	int32 n;
-	uint32 v;
-	uchar *p;
-
-	n = 0;
-	for(v = val; v >= 0x80; v >>= 7)
-		n++;
-	n++;
-
-	symgrow(s, s->np+n);
-
-	p = s->p + s->np - n;
-	for(v = val; v >= 0x80; v >>= 7)
-		*p++ = v | 0x80;
-	*p = v;
-}
-
-// funcpctab appends to dst a pc-value table mapping the code in func to the values
-// returned by valfunc parameterized by arg. The invocation of valfunc to update the
-// current value is, for each p,
-//
-//	val = valfunc(func, val, p, 0, arg);
-//	record val as value at p->pc;
-//	val = valfunc(func, val, p, 1, arg);
-//
-// where func is the function, val is the current value, p is the instruction being
-// considered, and arg can be used to further parameterize valfunc.
-void
-funcpctab(Sym *dst, Sym *func, char *desc, int32 (*valfunc)(Sym*, int32, Prog*, int32, int32), int32 arg)
-{
-	int dbg, i, start;
-	int32 oldval, val, started;
-	uint32 delta;
-	vlong pc;
-	Prog *p;
-
-	// To debug a specific function, uncomment second line and change name.
-	dbg = 0;
-	//dbg = strcmp(func->name, "main.main") == 0;
-
-	debug['O'] += dbg;
-
-	start = dst->np;
-
-	if(debug['O'])
-		Bprint(&bso, "funcpctab %s -> %s [valfunc=%s]\n", func->name, dst->name, desc);
-
-	val = -1;
-	oldval = val;
-	pc = func->value;
-	
-	if(debug['O'])
-		Bprint(&bso, "%6llux %6d %P\n", pc, val, func->text);
-
-	started = 0;
-	for(p=func->text; p != P; p = p->link) {
-		// Update val. If it's not changing, keep going.
-		val = valfunc(func, val, p, 0, arg);
-		if(val == oldval && started) {
-			val = valfunc(func, val, p, 1, arg);
-			if(debug['O'])
-				Bprint(&bso, "%6llux %6s %P\n", (vlong)p->pc, "", p);
-			continue;
-		}
-
-		// If the pc of the next instruction is the same as the
-		// pc of this instruction, this instruction is not a real
-		// instruction. Keep going, so that we only emit a delta
-		// for a true instruction boundary in the program.
-		if(p->link && p->link->pc == p->pc) {
-			val = valfunc(func, val, p, 1, arg);
-			if(debug['O'])
-				Bprint(&bso, "%6llux %6s %P\n", (vlong)p->pc, "", p);
-			continue;
-		}
-
-		// The table is a sequence of (value, pc) pairs, where each
-		// pair states that the given value is in effect from the current position
-		// up to the given pc, which becomes the new current position.
-		// To generate the table as we scan over the program instructions,
-		// we emit a "(value" when pc == func->value, and then
-		// each time we observe a change in value we emit ", pc) (value".
-		// When the scan is over, we emit the closing ", pc)".
-		//
-		// The table is delta-encoded. The value deltas are signed and
-		// transmitted in zig-zag form, where a complement bit is placed in bit 0,
-		// and the pc deltas are unsigned. Both kinds of deltas are sent
-		// as variable-length little-endian base-128 integers,
-		// where the 0x80 bit indicates that the integer continues.
-
-		if(debug['O'])
-			Bprint(&bso, "%6llux %6d %P\n", (vlong)p->pc, val, p);
-
-		if(started) {
-			addvarint(dst, (p->pc - pc) / MINLC);
-			pc = p->pc;
-		}
-		delta = val - oldval;
-		if(delta>>31)
-			delta = 1 | ~(delta<<1);
-		else
-			delta <<= 1;
-		addvarint(dst, delta);
-		oldval = val;
-		started = 1;
-		val = valfunc(func, val, p, 1, arg);
-	}
-
-	if(started) {
-		if(debug['O'])
-			Bprint(&bso, "%6llux done\n", (vlong)func->value+func->size);
-		addvarint(dst, (func->value+func->size - pc) / MINLC);
-		addvarint(dst, 0); // terminator
-	}
-
-	if(debug['O']) {
-		Bprint(&bso, "wrote %d bytes\n", dst->np - start);
-		for(i=start; i<dst->np; i++)
-			Bprint(&bso, " %02ux", dst->p[i]);
-		Bprint(&bso, "\n");
-	}
-
-	debug['O'] -= dbg;
-}
-
-// pctofileline computes either the file number (arg == 0)
-// or the line number (arg == 1) to use at p.
-// Because p->lineno applies to p, phase == 0 (before p)
-// takes care of the update.
-static int32
-pctofileline(Sym *sym, int32 oldval, Prog *p, int32 phase, int32 arg)
-{
-	int32 f, l;
-
-	if(p->as == ATEXT || p->as == ANOP || p->as == AUSEFIELD || p->line == 0 || phase == 1)
-		return oldval;
-	getline(sym->hist, p->line, &f, &l);
-	if(f == 0) {
-	//	print("getline failed for %s %P\n", cursym->name, p);
-		return oldval;
-	}
-	if(arg == 0)
-		return f;
-	return l;
-}
-
-// pctospadj computes the sp adjustment in effect.
-// It is oldval plus any adjustment made by p itself.
-// The adjustment by p takes effect only after p, so we
-// apply the change during phase == 1.
-static int32
-pctospadj(Sym *sym, int32 oldval, Prog *p, int32 phase, int32 arg)
-{
-	USED(arg);
-	USED(sym);
-
-	if(oldval == -1) // starting
-		oldval = 0;
-	if(phase == 0)
-		return oldval;
-	if(oldval + p->spadj < -10000 || oldval + p->spadj > 1100000000) {
-		diag("overflow in spadj: %d + %d = %d", oldval, p->spadj, oldval + p->spadj);
-		errorexit();
-	}
-	return oldval + p->spadj;
-}
-
-// pctopcdata computes the pcdata value in effect at p.
-// A PCDATA instruction sets the value in effect at future
-// non-PCDATA instructions.
-// Since PCDATA instructions have no width in the final code,
-// it does not matter which phase we use for the update.
-static int32
-pctopcdata(Sym *sym, int32 oldval, Prog *p, int32 phase, int32 arg)
-{
-	USED(sym);
-
-	if(phase == 0 || p->as != APCDATA || p->from.offset != arg)
-		return oldval;
-	if((int32)p->to.offset != p->to.offset) {
-		diag("overflow in PCDATA instruction: %P", p);
-		errorexit();
-	}
-	return p->to.offset;
-}
-
-#define	LOG	5
-void
-mkfwd(void)
-{
-	Prog *p;
-	int i;
-	int32 dwn[LOG], cnt[LOG];
-	Prog *lst[LOG];
-
-	for(i=0; i<LOG; i++) {
-		if(i == 0)
-			cnt[i] = 1;
-		else
-			cnt[i] = LOG * cnt[i-1];
-		dwn[i] = 1;
-		lst[i] = P;
-	}
-	i = 0;
-	for(cursym = textp; cursym != nil; cursym = cursym->next) {
-		for(p = cursym->text; p != P; p = p->link) {
-			if(p->link == P) {
-				if(cursym->next)
-					p->forwd = cursym->next->text;
-				break;
-			}
-			i--;
-			if(i < 0)
-				i = LOG-1;
-			p->forwd = P;
-			dwn[i]--;
-			if(dwn[i] <= 0) {
-				dwn[i] = cnt[i];
-				if(lst[i] != P)
-					lst[i]->forwd = p;
-				lst[i] = p;
-			}
-		}
-	}
-}
-
 uint16
 le16(uchar *b)
 {
@@ -1652,7 +962,7 @@ Endian le = { le16, le32, le64 };
 typedef struct Chain Chain;
 struct Chain
 {
-	Sym *sym;
+	LSym *sym;
 	Chain *up;
 	int limit;  // limit on entry to sym
 };
@@ -1660,8 +970,8 @@ struct Chain
 static int stkcheck(Chain*, int);
 static void stkprint(Chain*, int);
 static void stkbroke(Chain*, int);
-static Sym *morestack;
-static Sym *newstack;
+static LSym *morestack;
+static LSym *newstack;
 
 enum
 {
@@ -1673,16 +983,16 @@ void
 dostkcheck(void)
 {
 	Chain ch;
-	Sym *s;
+	LSym *s;
 	
-	morestack = lookup("runtime.morestack", 0);
-	newstack = lookup("runtime.newstack", 0);
+	morestack = linklookup(ctxt, "runtime.morestack", 0);
+	newstack = linklookup(ctxt, "runtime.newstack", 0);
 
 	// First the nosplits on their own.
-	for(s = textp; s != nil; s = s->next) {
-		if(s->text == nil || s->text->link == nil || (s->text->textflag & NOSPLIT) == 0)
+	for(s = ctxt->textp; s != nil; s = s->next) {
+		if(s->text == nil || s->text->link == nil || (ctxt->arch->textflag(s->text) & NOSPLIT) == 0)
 			continue;
-		cursym = s;
+		ctxt->cursym = s;
 		ch.up = nil;
 		ch.sym = s;
 		ch.limit = StackLimit - CallSize;
@@ -1695,10 +1005,10 @@ dostkcheck(void)
 	// like newproc and deferproc.	We could hard-code
 	// that knowledge but it's more robust to look at
 	// the actual call sites.
-	for(s = textp; s != nil; s = s->next) {
-		if(s->text == nil || s->text->link == nil || (s->text->textflag & NOSPLIT) != 0)
+	for(s = ctxt->textp; s != nil; s = s->next) {
+		if(s->text == nil || s->text->link == nil || (ctxt->arch->textflag(s->text) & NOSPLIT) != 0)
 			continue;
-		cursym = s;
+		ctxt->cursym = s;
 		ch.up = nil;
 		ch.sym = s;
 		ch.limit = StackLimit - CallSize;
@@ -1711,7 +1021,7 @@ stkcheck(Chain *up, int depth)
 {
 	Chain ch, ch1;
 	Prog *p;
-	Sym *s;
+	LSym *s;
 	int limit, prolog;
 	
 	limit = up->limit;
@@ -1732,7 +1042,7 @@ stkcheck(Chain *up, int depth)
 		// external function.
 		// should never be called directly.
 		// only diagnose the direct caller.
-		if(depth == 1)
+		if(depth == 1 && s->type != SXREF)
 			diag("call to external function %s", s->name);
 		return -1;
 	}
@@ -1748,7 +1058,7 @@ stkcheck(Chain *up, int depth)
 		return 0;
 
 	ch.up = up;
-	prolog = (s->text->textflag & NOSPLIT) == 0;
+	prolog = (ctxt->arch->textflag(s->text) & NOSPLIT) == 0;
 	for(p = s->text; p != P; p = p->link) {
 		limit -= p->spadj;
 		if(prolog && p->spadj != 0) {
@@ -1768,7 +1078,7 @@ stkcheck(Chain *up, int depth)
 			stkbroke(up, limit);
 			return -1;
 		}
-		if(iscall(p)) {
+		if(ctxt->arch->iscall(p)) {
 			limit -= CallSize;
 			ch.limit = limit;
 			if(p->to.type == D_BRANCH) {
@@ -1814,7 +1124,7 @@ stkprint(Chain *ch, int limit)
 
 	if(ch->up == nil) {
 		// top of chain.  ch->sym != nil.
-		if(ch->sym->text->textflag & NOSPLIT)
+		if(ctxt->arch->textflag(ch->sym->text) & NOSPLIT)
 			print("\t%d\tassumed on entry to %s\n", ch->limit, name);
 		else
 			print("\t%d\tguaranteed after split check in %s\n", ch->limit, name);
@@ -1855,25 +1165,15 @@ headstr(int v)
 	return buf;
 }
 
-void
-undef(void)
-{
-	Sym *s;
-
-	for(s = allsym; s != S; s = s->allsym)
-		if(s->type == SXREF)
-			diag("%s(%d): not defined", s->name, s->version);
-}
-
 int
 Yconv(Fmt *fp)
 {
-	Sym *s;
+	LSym *s;
 	Fmt fmt;
 	int i;
 	char *str;
 
-	s = va_arg(fp->args, Sym*);
+	s = va_arg(fp->args, LSym*);
 	if (s == S) {
 		fmtprint(fp, "<nil>");
 	} else {
@@ -1985,22 +1285,22 @@ doversion(void)
 }
 
 void
-genasmsym(void (*put)(Sym*, char*, int, vlong, vlong, int, Sym*))
+genasmsym(void (*put)(LSym*, char*, int, vlong, vlong, int, LSym*))
 {
 	Auto *a;
-	Sym *s;
+	LSym *s;
 	int32 off;
 
 	// These symbols won't show up in the first loop below because we
 	// skip STEXT symbols. Normal STEXT symbols are emitted by walking textp.
-	s = lookup("text", 0);
+	s = linklookup(ctxt, "text", 0);
 	if(s->type == STEXT)
 		put(s, s->name, 'T', s->value, s->size, s->version, 0);
-	s = lookup("etext", 0);
+	s = linklookup(ctxt, "etext", 0);
 	if(s->type == STEXT)
 		put(s, s->name, 'T', s->value, s->size, s->version, 0);
 
-	for(s=allsym; s!=S; s=s->allsym) {
+	for(s=ctxt->allsym; s!=S; s=s->allsym) {
 		if(s->hide || (s->name[0] == '.' && s->version == 0 && strcmp(s->name, ".rathole") != 0))
 			continue;
 		switch(s->type&SMASK) {
@@ -2036,7 +1336,7 @@ genasmsym(void (*put)(Sym*, char*, int, vlong, vlong, int, Sym*))
 		}
 	}
 
-	for(s = textp; s != nil; s = s->next) {
+	for(s = ctxt->textp; s != nil; s = s->next) {
 		if(s->text == nil)
 			continue;
 
@@ -2075,461 +1375,83 @@ genasmsym(void (*put)(Sym*, char*, int, vlong, vlong, int, Sym*))
 	Bflush(&bso);
 }
 
-char*
-estrdup(char *p)
-{
-	p = strdup(p);
-	if(p == nil) {
-		cursym = S;
-		diag("out of memory");
-		errorexit();
-	}
-	return p;
-}
-
-void*
-erealloc(void *p, long n)
+vlong
+symaddr(LSym *s)
 {
-	p = realloc(p, n);
-	if(p == nil) {
-		cursym = S;
-		diag("out of memory");
-		errorexit();
-	}
-	return p;
+	if(!s->reachable)
+		diag("unreachable symbol in symaddr - %s", s->name);
+	return s->value;
 }
 
-// Saved history stacks encountered while reading archives.
-// Keeping them allows us to answer virtual lineno -> file:line
-// queries.
-//
-// The history stack is a complex data structure, described best at the
-// bottom of http://plan9.bell-labs.com/magic/man2html/6/a.out.
-// One of the key benefits of interpreting it here is that the runtime
-// does not have to. Perhaps some day the compilers could generate
-// a simpler linker input too.
-
-struct Hist
-{
-	int32 line;
-	int32 off;
-	Sym *file;
-};
-
-static Hist *histcopy;
-static Hist *hist;
-static int32 nhist;
-static int32 maxhist;
-static int32 histdepth;
-static int32 nhistfile;
-static Sym *filesyms;
-
-// savehist processes a single line, off history directive
-// found in the input object file.
 void
-savehist(int32 line, int32 off)
+xdefine(char *p, int t, vlong v)
 {
-	char tmp[1024];
-	Sym *file;
-	Hist *h;
-
-	// NOTE(rsc): We used to do the copyhistfrog first and this
-	// condition was if(tmp[0] != '\0') to check for an empty string,
-	// implying that histfrogp == 0, implying that this is a history pop.
-	// However, on Windows in the misc/cgo test, the linker is
-	// presented with an ANAME corresponding to an empty string,
-	// that ANAME ends up being the only histfrog, and thus we have
-	// a situation where histfrogp > 0 (not a pop) but the path we find
-	// is the empty string. Really that shouldn't happen, but it doesn't
-	// seem to be bothering anyone yet, and it's easier to fix the condition
-	// to test histfrogp than to track down where that empty string is
-	// coming from. Probably it is coming from go tool pack's P command.
-	if(histfrogp > 0) {
-		tmp[0] = '\0';
-		copyhistfrog(tmp, sizeof tmp);
-		file = lookup(tmp, HistVersion);
-		if(file->type != SFILEPATH) {
-			file->value = ++nhistfile;
-			file->type = SFILEPATH;
-			file->next = filesyms;
-			filesyms = file;
-		}
-	} else
-		file = nil;
+	LSym *s;
 
-	if(file != nil && line == 1 && off == 0) {
-		// start of new stack
-		if(histdepth != 0) {
-			diag("history stack phase error: unexpected start of new stack depth=%d file=%s", histdepth, tmp);
-			errorexit();
-		}
-		nhist = 0;
-		histcopy = nil;
-	}
-	
-	if(nhist >= maxhist) {
-		if(maxhist == 0)
-			maxhist = 1;
-		maxhist *= 2;
-		hist = erealloc(hist, maxhist*sizeof hist[0]);
-	}
-	h = &hist[nhist++];
-	h->line = line;
-	h->off = off;
-	h->file = file;
-	
-	if(file != nil) {
-		if(off == 0)
-			histdepth++;
-	} else {
-		if(off != 0) {
-			diag("history stack phase error: bad offset in pop");
-			errorexit();
-		}
-		histdepth--;
-	}
+	s = linklookup(ctxt, p, 0);
+	s->type = t;
+	s->value = v;
+	s->reachable = 1;
+	s->special = 1;
 }
 
-// gethist returns the history stack currently in effect.
-// The result is valid indefinitely.
-Hist*
-gethist(void)
+vlong
+datoff(vlong addr)
 {
-	if(histcopy == nil) {
-		if(nhist == 0)
-			return nil;
-		histcopy = mal((nhist+1)*sizeof hist[0]);
-		memmove(histcopy, hist, nhist*sizeof hist[0]);
-		histcopy[nhist].line = -1;
-	}
-	return histcopy;
+	if(addr >= segdata.vaddr)
+		return addr - segdata.vaddr + segdata.fileoff;
+	if(addr >= segtext.vaddr)
+		return addr - segtext.vaddr + segtext.fileoff;
+	diag("datoff %#llx", addr);
+	return 0;
 }
 
-typedef struct Hstack Hstack;
-struct Hstack
-{
-	Hist *h;
-	int delta;
-};
-
-// getline sets *f to the file number and *l to the line number
-// of the virtual line number line according to the history stack h.
-void
-getline(Hist *h, int32 line, int32 *f, int32 *l)
+vlong
+entryvalue(void)
 {
-	Hstack stk[100];
-	int nstk, start;
-	Hist *top, *h0;
-	static Hist *lasth;
-	static int32 laststart, lastend, lastdelta, lastfile;
-
-	h0 = h;
-	*f = 0;
-	*l = 0;
-	start = 0;
-	if(h == nil || line == 0) {
-		print("%s: getline: h=%p line=%d\n", cursym->name, h, line);
-		return;
-	}
-
-	// Cache span used during last lookup, so that sequential
-	// translation of line numbers in compiled code is efficient.
-	if(!debug['O'] && lasth == h && laststart <= line && line < lastend) {
-		*f = lastfile;
-		*l = line - lastdelta;
-		return;
-	}
-
-	if(debug['O'])
-		print("getline %d laststart=%d lastend=%d\n", line, laststart, lastend);
-	
-	nstk = 0;
-	for(; h->line != -1; h++) {
-		if(debug['O'])
-			print("\t%s %d %d\n", h->file ? h->file->name : "?", h->line, h->off);
-
-		if(h->line > line) {
-			if(nstk == 0) {
-				diag("history stack phase error: empty stack at line %d", (int)line);
-				errorexit();
-			}
-			top = stk[nstk-1].h;
-			lasth = h;
-			lastfile = top->file->value;
-			laststart = start;
-			lastend = h->line;
-			lastdelta = stk[nstk-1].delta;
-			*f = lastfile;
-			*l = line - lastdelta;
-			if(debug['O'])
-				print("\tgot %d %d [%d %d %d]\n", *f, *l, laststart, lastend, lastdelta);
-			return;
-		}
-		if(h->file == nil) {
-			// pop included file
-			if(nstk == 0) {
-				diag("history stack phase error: stack underflow");
-				errorexit();
-			}
-			nstk--;
-			if(nstk > 0)
-				stk[nstk-1].delta += h->line - stk[nstk].h->line;
-			start = h->line;
-		} else if(h->off == 0) {
-			// push included file
-			if(nstk >= nelem(stk)) {
-				diag("history stack phase error: stack overflow");
-				errorexit();
-			}
-			start = h->line;
-			stk[nstk].h = h;
-			stk[nstk].delta = h->line - 1;
-			nstk++;
-		} else {
-			// #line directive
-			if(nstk == 0) {
-				diag("history stack phase error: stack underflow");
-				errorexit();
-			}
-			stk[nstk-1].h = h;
-			stk[nstk-1].delta = h->line - h->off;
-			start = h->line;
-		}
-		if(debug['O'])
-			print("\t\tnstk=%d delta=%d\n", nstk, stk[nstk].delta);
-	}
+	char *a;
+	LSym *s;
 
-	diag("history stack phase error: cannot find line for %d", line);
-	nstk = 0;
-	for(h = h0; h->line != -1; h++) {
-		print("\t%d %d %s\n", h->line, h->off, h->file ? h->file->name : "");
-		if(h->file == nil)
-			nstk--;
-		else if(h->off == 0)
-			nstk++;
-	}
+	a = INITENTRY;
+	if(*a >= '0' && *a <= '9')
+		return atolwhex(a);
+	s = linklookup(ctxt, a, 0);
+	if(s->type == 0)
+		return INITTEXT;
+	if(s->type != STEXT)
+		diag("entry not text: %s", s->name);
+	return s->value;
 }
 
-// defgostring returns a symbol for the Go string containing text.
-Sym*
-defgostring(char *text)
+static void
+undefsym(LSym *s)
 {
-	char *p;
-	Sym *s;
-	int32 n;
-	
-	n = strlen(text);
-	p = smprint("go.string.\"%Z\"", text);
-	s = lookup(p, 0);
-	if(s->size == 0) {
-		s->type = SGOSTRING;
-		s->reachable = 1;
-		s->size = 2*PtrSize+n;
-		symgrow(s, 2*PtrSize+n);
-		setaddrplus(s, 0, s, 2*PtrSize);
-		setuintxx(s, PtrSize, n, PtrSize);
-		memmove(s->p+2*PtrSize, text, n);
-	}
-	s->reachable = 1;
-	return s;
-}
+	int i;
+	Reloc *r;
 
-// addpctab appends to f a pc-value table, storing its offset at off.
-// The pc-value table is for func and reports the value of valfunc
-// parameterized by arg.
-static int32
-addpctab(Sym *f, int32 off, Sym *func, char *desc, int32 (*valfunc)(Sym*, int32, Prog*, int32, int32), int32 arg)
-{
-	int32 start;
-	
-	start = f->np;
-	funcpctab(f, func, desc, valfunc, arg);
-	if(start == f->np) {
-		// no table
-		return setuint32(f, off, 0);
-	}
-	if((int32)start > (int32)f->np) {
-		diag("overflow adding pc-table: symbol too large");
-		errorexit();
+	ctxt->cursym = s;
+	for(i=0; i<s->nr; i++) {
+		r = &s->r[i];
+		if(r->sym == nil) // happens for some external ARM relocs
+			continue;
+		if(r->sym->type == Sxxx || r->sym->type == SXREF) {
+			diag("undefined: %s", r->sym->name);
+			continue;
+		}
+		if(!r->sym->reachable)
+			diag("use of unreachable symbol: %s", r->sym->name);
 	}
-	return setuint32(f, off, start);
-}
-
-static int32
-ftabaddstring(Sym *ftab, char *s)
-{
-	int32 n, start;
-	
-	n = strlen(s)+1;
-	start = ftab->np;
-	symgrow(ftab, start+n+1);
-	strcpy((char*)ftab->p + start, s);
-	return start;
 }
 
-// pclntab initializes the pclntab symbol with
-// runtime function and file name information.
 void
-pclntab(void)
+undef(void)
 {
-	Prog *p;
-	int32 i, n, nfunc, start, funcstart;
-	uint32 *havepc, *havefunc;
-	Sym *ftab, *s;
-	int32 npcdata, nfuncdata, off, end;
-	int64 funcdata_bytes;
-	
-	funcdata_bytes = 0;
-	ftab = lookup("pclntab", 0);
-	ftab->type = SPCLNTAB;
-	ftab->reachable = 1;
-
-	// See golang.org/s/go12symtab for the format. Briefly:
-	//	8-byte header
-	//	nfunc [PtrSize bytes]
-	//	function table, alternating PC and offset to func struct [each entry PtrSize bytes]
-	//	end PC [PtrSize bytes]
-	//	offset to file table [4 bytes]
-	nfunc = 0;
-	for(cursym = textp; cursym != nil; cursym = cursym->next)
-		nfunc++;
-	symgrow(ftab, 8+PtrSize+nfunc*2*PtrSize+PtrSize+4);
-	setuint32(ftab, 0, 0xfffffffb);
-	setuint8(ftab, 6, MINLC);
-	setuint8(ftab, 7, PtrSize);
-	setuintxx(ftab, 8, nfunc, PtrSize);
-
-	nfunc = 0;
-	for(cursym = textp; cursym != nil; cursym = cursym->next, nfunc++) {
-		funcstart = ftab->np;
-		funcstart += -ftab->np & (PtrSize-1);
-
-		setaddr(ftab, 8+PtrSize+nfunc*2*PtrSize, cursym);
-		setuintxx(ftab, 8+PtrSize+nfunc*2*PtrSize+PtrSize, funcstart, PtrSize);
-
-		npcdata = 0;
-		nfuncdata = 0;
-		for(p = cursym->text; p != P; p = p->link) {
-			if(p->as == APCDATA && p->from.offset >= npcdata)
-				npcdata = p->from.offset+1;
-			if(p->as == AFUNCDATA && p->from.offset >= nfuncdata)
-				nfuncdata = p->from.offset+1;
-		}
-
-		// fixed size of struct, checked below
-		off = funcstart;
-		end = funcstart + PtrSize + 3*4 + 5*4 + npcdata*4 + nfuncdata*PtrSize;
-		if(nfuncdata > 0 && (end&(PtrSize-1)))
-			end += 4;
-		symgrow(ftab, end);
-
-		// entry uintptr
-		off = setaddr(ftab, off, cursym);
-
-		// name int32
-		off = setuint32(ftab, off, ftabaddstring(ftab, cursym->name));
-		
-		// args int32
-		// TODO: Move into funcinfo.
-		if(cursym->text == nil)
-			off = setuint32(ftab, off, ArgsSizeUnknown);
-		else
-			off = setuint32(ftab, off, cursym->args);
-	
-		// frame int32
-		// TODO: Remove entirely. The pcsp table is more precise.
-		// This is only used by a fallback case during stack walking
-		// when a called function doesn't have argument information.
-		// We need to make sure everything has argument information
-		// and then remove this.
-		if(cursym->text == nil)
-			off = setuint32(ftab, off, 0);
-		else
-			off = setuint32(ftab, off, (uint32)cursym->text->to.offset+PtrSize);
-
-		// pcsp table (offset int32)
-		off = addpctab(ftab, off, cursym, "pctospadj", pctospadj, 0);
-
-		// pcfile table (offset int32)
-		off = addpctab(ftab, off, cursym, "pctofileline file", pctofileline, 0);
-
-		// pcln table (offset int32)
-		off = addpctab(ftab, off, cursym, "pctofileline line", pctofileline, 1);
-		
-		// npcdata int32
-		off = setuint32(ftab, off, npcdata);
-		
-		// nfuncdata int32
-		off = setuint32(ftab, off, nfuncdata);
-		
-		// tabulate which pc and func data we have.
-		n = ((npcdata+31)/32 + (nfuncdata+31)/32)*4;
-		havepc = mal(n);
-		havefunc = havepc + (npcdata+31)/32;
-		for(p = cursym->text; p != P; p = p->link) {
-			if(p->as == AFUNCDATA) {
-				if((havefunc[p->from.offset/32]>>(p->from.offset%32))&1)
-					diag("multiple definitions for FUNCDATA $%d", p->from.offset);
-				havefunc[p->from.offset/32] |= 1<<(p->from.offset%32);
-			}
-			if(p->as == APCDATA)
-				havepc[p->from.offset/32] |= 1<<(p->from.offset%32);
-		}
-
-		// pcdata.
-		for(i=0; i<npcdata; i++) {
-			if(!(havepc[i/32]>>(i%32))&1) {
-				off = setuint32(ftab, off, 0);
-				continue;
-			}
-			off = addpctab(ftab, off, cursym, "pctopcdata", pctopcdata, i);
-		}
-		
-		unmal(havepc, n);
-		
-		// funcdata, must be pointer-aligned and we're only int32-aligned.
-		// Unlike pcdata, can gather in a single pass.
-		// Missing funcdata will be 0 (nil pointer).
-		if(nfuncdata > 0) {
-			if(off&(PtrSize-1))
-				off += 4;
-			for(p = cursym->text; p != P; p = p->link) {
-				if(p->as == AFUNCDATA) {
-					i = p->from.offset;
-					if(p->to.type == D_CONST)
-						setuintxx(ftab, off+PtrSize*i, p->to.offset, PtrSize);
-					else {
-						// TODO: Dedup.
-						funcdata_bytes += p->to.sym->size;
-						setaddrplus(ftab, off+PtrSize*i, p->to.sym, p->to.offset);
-					}
-				}
-			}
-			off += nfuncdata*PtrSize;
-		}
-
-		if(off != end) {
-			diag("bad math in functab: funcstart=%d off=%d but end=%d (npcdata=%d nfuncdata=%d)", funcstart, off, end, npcdata, nfuncdata);
-			errorexit();
-		}
-	
-		// Final entry of table is just end pc.
-		if(cursym->next == nil)
-			setaddrplus(ftab, 8+PtrSize+(nfunc+1)*2*PtrSize, cursym, cursym->size);
-	}
+	LSym *s;
 	
-	// Start file table.
-	start = ftab->np;
-	start += -ftab->np & (PtrSize-1);
-	setuint32(ftab, 8+PtrSize+nfunc*2*PtrSize+PtrSize, start);
-
-	symgrow(ftab, start+(nhistfile+1)*4);
-	setuint32(ftab, start, nhistfile);
-	for(s = filesyms; s != S; s = s->next)
-		setuint32(ftab, start + s->value*4, ftabaddstring(ftab, s->name));
-
-	ftab->size = ftab->np;
-	
-	if(debug['v'])
-		Bprint(&bso, "%5.2f pclntab=%lld bytes, funcdata total %lld bytes\n", cputime(), (vlong)ftab->size, (vlong)funcdata_bytes);
-}	
+	for(s = ctxt->textp; s != nil; s = s->next)
+		undefsym(s);
+	for(s = datap; s != nil; s = s->next)
+		undefsym(s);
+	if(nerrors > 0)
+		errorexit();
+}