add common linkage for data

all.h

@@ -371,6 +371,7 @@ struct Addr { /* amd64 addressing */
 struct Lnk {
 	char export;
 	char thread;
+	char common;
 	char align;
 	char *sec;
 	char *secf;

emit.c

@@ -75,7 +75,17 @@ emitdat(Dat *d, FILE *f)
 		zero = 0;
 		break;
 	case DEnd:
-		if (zero != -1) {
+		if (d->lnk->common) {
+			if (zero == -1)
+				die("invalid common data definition");
+			p = d->name[0] == '"' ? "" : T.assym;
+			fprintf(f, ".comm %s%s,%"PRId64,
+				p, d->name, zero);
+			if (d->lnk->align)
+				fprintf(f, ",%d", d->lnk->align);
+			fputc('\n', f);
+		}
+		else if (zero != -1) {
 			emitlnk(d->name, d->lnk, SecBss, f);
 			fprintf(f, "\t.fill %"PRId64",1,0\n", zero);
 		}
@@ -87,6 +97,8 @@ emitdat(Dat *d, FILE *f)
 			fprintf(f, "\t.fill %"PRId64",1,0\n", d->u.num);
 		break;
 	default:
+		if (d->lnk->common)
+			die("unsupported common data item");
 		if (zero != -1) {
 			emitlnk(d->name, d->lnk, SecData, f);
 			if (zero > 0)

parse.c

@@ -48,6 +48,7 @@ enum Token {
 	Thlt,
 	Texport,
 	Tthread,
+	Tcommon,
 	Tfunc,
 	Ttype,
 	Tdata,
@@ -106,6 +107,7 @@ static char *kwmap[Ntok] = {
 	[Thlt] = "hlt",
 	[Texport] = "export",
 	[Tthread] = "thread",
+	[Tcommon] = "common",
 	[Tfunc] = "function",
 	[Ttype] = "type",
 	[Tdata] = "data",
@@ -132,7 +134,7 @@ enum {
 	TMask = 16383, /* for temps hash */
 	BMask = 8191, /* for blocks hash */
 
-	K = 9583425, /* found using tools/lexh.c */
+	K = 11183273, /* found using tools/lexh.c */
 	M = 23,
 };
 
@@ -1159,6 +1161,9 @@ parselnk(Lnk *lnk)
 		case Tthread:
 			lnk->thread = 1;
 			break;
+		case Tcommon:
+			lnk->common = 1;
+			break;
 		case Tsection:
 			if (lnk->sec)
 				err("only one section allowed");

tools/lexh.c

@@ -29,7 +29,7 @@ char *tok[] = {
 	"function", "type", "data", "section", "align", "dbgfile",
 	"blit", "l", "w", "sh", "uh", "h", "sb", "ub", "b",
 	"d", "s", "z", "loadw", "loadl", "loads", "loadd",
-	"alloc1", "alloc2",
+	"alloc1", "alloc2", "thread", "common",
 
 };
 enum {