gc, ld: detect stale or incompatible object files

The object files begin with a header that is

        $GOARCH

on a line by itself.  This CL changes that header to

        go object $GOOS $GOARCH release.2011-01-01 4567+

where the final two fields are the most recent release
tag and the current hg version number.

All objects imported into a Go compilation or linked into an
executable must have the same header line, and that header
line must match the compiler and linker versions.

The effect of this will be that if you update and run all.bash
and then try to link in objects compiled with an earlier version
of the compiler (or invoke the wrong version of the compiler),
you will get an error showing the different headers instead
of perhaps silent incompatibility.

Normal usage with all.bash should be unaffected, because
all.bash deletes all the object files in $GOROOT/pkg/$GOOS_$GOARCH
and cleans all intermediate object files before starting.

This change is intended to diagnose stale objects arising when
users maintaining alternate installation directories forget to
rebuild some of their files after updating.

It should help make the adoption of $GOPATH (CL 3780043)
less error-prone.

R=ken2, r
CC=golang-dev
http://codereview.appspot.com/4023063

14 files changed, 110 insertions, 53 deletions

diff --git a/src/cmd/5a/lex.c b/src/cmd/5a/lex.c
index b36094a78..e762f5646 100644
--- a/src/cmd/5a/lex.c
+++ b/src/cmd/5a/lex.c
@@ -187,7 +187,7 @@ assemble(char *file)
 	pass = 1;
 	pinit(file);
 
-	Bprint(&obuf, "%s\n", thestring);
+	Bprint(&obuf, "go object %s %s %s\n", getgoos(), thestring, getgoversion());
 
 	for(i=0; i<nDlist; i++)
 		dodefine(Dlist[i]);
diff --git a/src/cmd/5c/swt.c b/src/cmd/5c/swt.c
index 43eb73c94..d45aabc5e 100644
--- a/src/cmd/5c/swt.c
+++ b/src/cmd/5c/swt.c
@@ -373,7 +373,7 @@ outcode(void)
 		}
 	}
 
-	Bprint(&outbuf, "%s\n", thestring);
+	Bprint(&outbuf, "go object %s %s %s\n", getgoos(), thestring, getgoversion());
 	if(ndynimp > 0 || ndynexp > 0) {
 		int i;
 
diff --git a/src/cmd/6a/lex.c b/src/cmd/6a/lex.c
index 1b8bb6344..37144c888 100644
--- a/src/cmd/6a/lex.c
+++ b/src/cmd/6a/lex.c
@@ -189,7 +189,7 @@ assemble(char *file)
 	pass = 1;
 	pinit(file);
 
-	Bprint(&obuf, "%s\n", thestring);
+	Bprint(&obuf, "go object %s %s %s\n", getgoos(), thestring, getgoversion());
 
 	for(i=0; i<nDlist; i++)
 		dodefine(Dlist[i]);
diff --git a/src/cmd/6c/swt.c b/src/cmd/6c/swt.c
index 47975a0c8..6d886f459 100644
--- a/src/cmd/6c/swt.c
+++ b/src/cmd/6c/swt.c
@@ -231,7 +231,7 @@ outcode(void)
 	}
 	Binit(&b, f, OWRITE);
 
-	Bprint(&b, "%s\n", thestring);
+	Bprint(&b, "go object %s %s %s\n", getgoos(), thestring, getgoversion());
 	if(ndynimp > 0 || ndynexp > 0) {
 		int i;
 
diff --git a/src/cmd/8a/lex.c b/src/cmd/8a/lex.c
index bf298b266..d5fa959aa 100644
--- a/src/cmd/8a/lex.c
+++ b/src/cmd/8a/lex.c
@@ -189,7 +189,7 @@ assemble(char *file)
 	pass = 1;
 	pinit(file);
 
-	Bprint(&obuf, "%s\n", thestring);
+	Bprint(&obuf, "go object %s %s %s\n", getgoos(), thestring, getgoversion());
 
 	for(i=0; i<nDlist; i++)
 		dodefine(Dlist[i]);
diff --git a/src/cmd/8c/swt.c b/src/cmd/8c/swt.c
index be48885f8..d07a5439c 100644
--- a/src/cmd/8c/swt.c
+++ b/src/cmd/8c/swt.c
@@ -230,7 +230,7 @@ outcode(void)
 	}
 	Binit(&b, f, OWRITE);
 
-	Bprint(&b, "%s\n", thestring);
+	Bprint(&b, "go object %s %s %s\n", getgoos(), thestring, getgoversion());
 	if(ndynimp > 0 || ndynexp > 0) {
 		int i;
 
diff --git a/src/cmd/gc/align.c b/src/cmd/gc/align.c
index ed20e7e8b..833eba19a 100644
--- a/src/cmd/gc/align.c
+++ b/src/cmd/gc/align.c
@@ -54,7 +54,8 @@ widstruct(Type *t, uint32 o, int flag)
 		if(f->type->width < 0)
 			fatal("invalid width %lld", f->type->width);
 		w = f->type->width;
-		o = rnd(o, f->type->align);
+		if(f->type->align > 0)
+			o = rnd(o, f->type->align);
 		f->width = o;	// really offset for TFIELD
 		if(f->nname != N) {
 			// this same stackparam logic is in addrescapes
diff --git a/src/cmd/gc/lex.c b/src/cmd/gc/lex.c
index 45b1257fa..2148d7523 100644
--- a/src/cmd/gc/lex.c
+++ b/src/cmd/gc/lex.c
@@ -405,7 +405,7 @@ void
 importfile(Val *f, int line)
 {
 	Biobuf *imp;
-	char *file;
+	char *file, *p, *q;
 	int32 c;
 	int len;
 	Strlit *path;
@@ -432,7 +432,7 @@ importfile(Val *f, int line)
 		cannedimports("unsafe.6", unsafeimport);
 		return;
 	}
-
+	
 	path = f->u.sval;
 	if(islocalname(path)) {
 		cleanbuf = mal(strlen(pathname) + strlen(path->s) + 2);
@@ -459,10 +459,25 @@ importfile(Val *f, int line)
 	len = strlen(namebuf);
 	if(len > 2 && namebuf[len-2] == '.' && namebuf[len-1] == 'a') {
 		if(!skiptopkgdef(imp)) {
-			yyerror("import not package file: %s", namebuf);
+			yyerror("import %s: not a package file", file);
 			errorexit();
 		}
 	}
+	
+	// check object header
+	p = Brdstr(imp, '\n', 1);
+	if(strcmp(p, "empty archive") != 0) {
+		if(strncmp(p, "go object ", 10) != 0) {
+			yyerror("import %s: not a go object file", file);
+			errorexit();
+		}
+		q = smprint("%s %s %s", getgoos(), thestring, getgoversion());
+		if(strcmp(p+10, q) != 0) {
+			yyerror("import %s: object is [%s] expected [%s]", file, p+10, q);
+			errorexit();
+		}
+		free(q);
+	}
 
 	// assume files move (get installed)
 	// so don't record the full path.
@@ -479,6 +494,7 @@ importfile(Val *f, int line)
 	curio.infile = file;
 	curio.nlsemi = 0;
 	typecheckok = 1;
+
 	for(;;) {
 		c = getc();
 		if(c == EOF)
diff --git a/src/cmd/gc/obj.c b/src/cmd/gc/obj.c
index 0d0d70ac9..fbabe0d43 100644
--- a/src/cmd/gc/obj.c
+++ b/src/cmd/gc/obj.c
@@ -21,7 +21,7 @@ dumpobj(void)
 		errorexit();
 	}
 
-	Bprint(bout, "%s\n", thestring);
+	Bprint(bout, "go object %s %s %s\n", getgoos(), thestring, getgoversion());
 	Bprint(bout, "  exports automatically generated from\n");
 	Bprint(bout, "  %s in package \"%s\"\n", curio.infile, localpkg->name);
 	dumpexport();
diff --git a/src/cmd/gc/subr.c b/src/cmd/gc/subr.c
index cb5e2a831..0755ca3cd 100644
--- a/src/cmd/gc/subr.c
+++ b/src/cmd/gc/subr.c
@@ -203,6 +203,7 @@ fatal(char *fmt, ...)
 
 	flusherrors();
 
+*(int*)0=0;
 	print("%L: internal compiler error: ", lineno);
 	va_start(arg, fmt);
 	vfprint(1, fmt, arg);
@@ -213,7 +214,7 @@ fatal(char *fmt, ...)
 	if(strncmp(getgoversion(), "release", 7) == 0) {
 		print("\n");
 		print("Please file a bug report including a short program that triggers the error.\n");
-		print("http://code.google.com/p/go/issues/entry?template=compilerbug");
+		print("http://code.google.com/p/go/issues/entry?template=compilerbug\n");
 	}
 	hcrash();
 	errorexit();
diff --git a/src/cmd/gopack/ar.c b/src/cmd/gopack/ar.c
index a16e98cfe..eed98967a 100644
--- a/src/cmd/gopack/ar.c
+++ b/src/cmd/gopack/ar.c
@@ -131,6 +131,7 @@ Arfile *astart, *amiddle, *aend;	/* Temp file control block pointers */
 int	allobj = 1;			/* set when all members are object files of the same type */
 int	symdefsize;			/* size of symdef file */
 char	*pkgstmt;		/* string "package foo" */
+char	*objhdr;		/* string "go object darwin 386 release.2010-01-01 2345+" */
 int	dupfound;			/* flag for duplicate symbol */
 Hashchain	*hash[NHASH];		/* hash table of text symbols */
 
@@ -246,6 +247,8 @@ main(int argc, char *argv[])
 	argc -= 3;
 	argv += 3;
 	(*comfun)(cp, argc, argv);	/* do the command */
+	if(errors && cflag)
+		remove(cp);
 	cp = 0;
 	while (argc--) {
 		if (*argv) {
@@ -590,10 +593,11 @@ void
 scanobj(Biobuf *b, Arfile *ap, long size)
 {
 	int obj;
-	vlong offset;
+	vlong offset, offset1;
 	Dir *d;
 	static int lastobj = -1;
 	uchar buf[4];
+	char *p, *t;
 
 	if (!allobj)			/* non-object file encountered */
 		return;
@@ -628,14 +632,32 @@ scanobj(Biobuf *b, Arfile *ap, long size)
 		Bseek(b, offset, 0);
 		return;
 	}
-	if (lastobj >= 0 && obj != lastobj) {
+
+	offset1 = Boffset(b);
+	Bseek(b, offset, 0);
+	p = Brdstr(b, '\n', 1);
+	Bseek(b, offset1, 0);
+	if(p == nil || strncmp(p, "go object ", 10) != 0) {
+		fprint(2, "gopack: malformed object file %s\n", file);
+		errors++;
+		Bseek(b, offset, 0);
+		free(p);
+		return;
+	}
+	
+	if ((lastobj >= 0 && obj != lastobj) || (objhdr != nil && strcmp(p, objhdr) != 0)) {
 		fprint(2, "gopack: inconsistent object file %s\n", file);
 		errors++;
 		allobj = 0;
-		Bseek(b, offset, 0);
+		free(p);
 		return;
 	}
 	lastobj = obj;
+	if(objhdr == nil)
+		objhdr = p;
+	else
+		free(p);
+		
 	if (!readar(b, obj, offset+size, 0)) {
 		fprint(2, "gopack: invalid symbol reference in file %s\n", file);
 		errors++;
@@ -677,7 +699,7 @@ char*	importblock;
 void
 getpkgdef(char **datap, int *lenp)
 {
-	char *tag;
+	char *tag, *hdr;
 
 	if(pkgname == nil) {
 		pkgname = "__emptyarchive__";
@@ -688,7 +710,11 @@ getpkgdef(char **datap, int *lenp)
 	if(safe || Sflag)
 		tag = "safe";
 
-	*datap = smprint("import\n$$\npackage %s %s\n%s\n$$\n", pkgname, tag, importblock);
+	hdr = "empty archive";
+	if(objhdr != nil)
+		hdr = objhdr;
+
+	*datap = smprint("%s\nimport\n$$\npackage %s %s\n%s\n$$\n", hdr, pkgname, tag, importblock);
 	*lenp = strlen(*datap);
 }
 
diff --git a/src/cmd/ld/lib.c b/src/cmd/ld/lib.c
index b1a62f25e..0c9ea0b7c 100644
--- a/src/cmd/ld/lib.c
+++ b/src/cmd/ld/lib.c
@@ -378,10 +378,10 @@ ldobj(Biobuf *f, char *pkg, int64 len, char *pn, int whence)
 	int n, c1, c2, c3, c4;
 	uint32 magic;
 	vlong import0, import1, eof;
-	char src[1024];
+	char *fld[10], *s, *t;
+	int nfld;
 
 	eof = Boffset(f) + len;
-	src[0] = '\0';
 
 	pn = strdup(pn);
 	
@@ -415,22 +415,34 @@ ldobj(Biobuf *f, char *pkg, int64 len, char *pn, int whence)
 	line = Brdline(f, '\n');
 	if(line == nil) {
 		if(Blinelen(f) > 0) {
-			diag("%s: malformed object file", pn);
+			diag("%s: not an object file", pn);
 			return;
 		}
 		goto eof;
 	}
 	n = Blinelen(f) - 1;
-	if(n != strlen(thestring) || strncmp(line, thestring, n) != 0) {
-		if(line)
-			line[n] = '\0';
+	line[n] = '\0';
+	if(strncmp(line, "go object ", 10) != 0) {
 		if(strlen(pn) > 3 && strcmp(pn+strlen(pn)-3, ".go") == 0) {
 			print("%cl: input %s is not .%c file (use %cg to compile .go files)\n", thechar, pn, thechar, thechar);
 			errorexit();
 		}
-		diag("file not %s [%s]\n", thestring, line);
+		if(strcmp(line, thestring) == 0) {
+			// old header format: just $GOOS
+			diag("%s: stale object file", pn);
+			return;
+		}
+		diag("%s: not an object file", pn);
+		return;
+	}
+	t = smprint("%s %s %s", getgoos(), thestring, getgoversion());
+	if(strcmp(line+10, t) != 0) {
+		diag("%s: object is [%s] expected [%s]", pn, line+10, t);
+		free(t);
 		return;
 	}
+	free(t);
+	line[n] = '\n';
 
 	/* skip over exports and other info -- ends with \n!\n */
 	import0 = Boffset(f);
diff --git a/src/libmach/obj.c b/src/libmach/obj.c
index dacb2ae1f..1ffe7a0ee 100644
--- a/src/libmach/obj.c
+++ b/src/libmach/obj.c
@@ -116,34 +116,24 @@ objtype(Biobuf *bp, char **name)
 	int i;
 	char buf[MAXIS];
 	int c;
-
-Retry:
-	if(Bread(bp, buf, MAXIS) < MAXIS)
-		return -1;
-	Bseek(bp, -MAXIS, 1);
-	for (i = 0; i < Maxobjtype; i++) {
-		if (obj[i].is && (*obj[i].is)(buf)) {
-			if (name)
-				*name = obj[i].name;
-			return i;
-		}
-	}
+	char *p;
 
 	/*
-	 * Maybe there's an import block we need to skip
+	 * Look for import block.
 	 */
-	for(i = 0; i < MAXIS; i++) {
-		if(isalpha(buf[i]) || isdigit(buf[i]))
-			continue;
-		if(i == 0 || buf[i] != '\n')
-			return -1;
-		break;
-	}
+	p = Brdline(bp, '\n');
+	if(p == nil)
+		return -1;
+	if(Blinelen(bp) < 10 || strncmp(p, "go object ", 10) != 0)
+		return -1;
+	Bseek(bp, -1, 1);
 
 	/*
 	 * Found one.  Skip until "\n!\n"
 	 */
-	while((c = Bgetc(bp)) != Beof) {
+	for(;;) {
+		if((c = Bgetc(bp)) == Beof)
+			return -1;
 		if(c != '\n')
 			continue;
 		c = Bgetc(bp);
@@ -156,8 +146,20 @@ Retry:
 			Bungetc(bp);
 			continue;
 		}
-		goto Retry;
+		break;
 	}
+
+	if(Bread(bp, buf, MAXIS) < MAXIS)
+		return -1;
+	Bseek(bp, -MAXIS, 1);
+	for (i = 0; i < Maxobjtype; i++) {
+		if (obj[i].is && (*obj[i].is)(buf)) {
+			if (name)
+				*name = obj[i].name;
+			return i;
+		}
+	}
+
 	return -1;
 }
 
diff --git a/src/version.bash b/src/version.bash
index 2d29825ff..0e6483150 100755
--- a/src/version.bash
+++ b/src/version.bash
@@ -11,17 +11,16 @@ fi
 
 # Get numerical revision
 VERSION=$(hg identify -n 2>/dev/null)
-if [ $? = 0 ]; then
-	TAG=$(hg identify -t | sed 's!/release!!')
-else
+if [ $? != 0 ]; then
 	OLD=$(hg identify | sed 1q)
 	VERSION=$(echo $OLD | awk '{print $1}')
-	TAG=$(echo $OLD | awk '{print $2}' | sed 's!/release!!')
 fi
 
-# Append tag if not 'tip'
-if [[ "$TAG" != "tip" ]]; then
-	VERSION="$VERSION $TAG"
+# Find most recent known release tag.
+TAG=$(hg tags | awk '$1~/^release\./ {print $1}' | sed -n 1p)
+
+if [ "$TAG" != "" ]; then
+	VERSION="$TAG $VERSION"
 fi
 
 echo $VERSION