[dev.power64] cmd/9a: use new flag parser

Copy main from 6a. Fixes various things, but the
main thing is the use of the new flag parser.
The go command expects to be able to use -trimpath
and not have it be interpreted as -t rimpath.

LGTM=minux
R=minux
CC=golang-codereviews
https://golang.org/cl/126100043

src/cmd/9a/lex.c

@@ -50,30 +50,54 @@ systemtype(int sys)
 #endif
 }
 
+int
+pathchar(void)
+{
+	return '/';
+}
+
 int
 Lconv(Fmt *fp)
 {
 	return linklinefmt(ctxt, fp);
 }
 
-int
-pathchar(void)
+void
+dodef(char *p)
 {
-	return '/';
+	if(nDlist%8 == 0)
+		Dlist = allocn(Dlist, nDlist*sizeof(char *),
+			8*sizeof(char *));
+	Dlist[nDlist++] = p;
+}
+
+LinkArch*       thelinkarch = &linkpower64;
+
+void
+usage(void)
+{
+	print("usage: %ca [options] file.c...\n", thechar);
+	flagprint(1);
+	errorexit();
 }
 
 void
 main(int argc, char *argv[])
 {
 	char *p;
-	int c;
 
 	thechar = '9';
-	thestring = getgoarch();
-	if(strcmp(thestring, "power64le") == 0)
-		ctxt = linknew(&linkpower64le);
-	else
-		ctxt = linknew(&linkpower64);
+	thestring = "power64";
+
+	// Allow GOARCH=thestring or GOARCH=thestringsuffix,
+	// but not other values.	
+	p = getgoarch();
+	if(strncmp(p, thestring, strlen(thestring)) != 0)
+		sysfatal("cannot use %cc with GOARCH=%s", thechar, p);
+	if(strcmp(p, "power64le") == 0)
+		thelinkarch = &linkpower64le;
+
+	ctxt = linknew(thelinkarch);
 	ctxt->diag = yyerror;
 	ctxt->bso = &bstdout;
 	Binit(&bstdout, 1, OWRITE);
@@ -85,79 +109,57 @@ main(int argc, char *argv[])
 	cinit();
 	outfile = 0;
 	setinclude(".");
-	ARGBEGIN {
-	default:
-		c = ARGC();
-		if(c >= 0 && c < sizeof(debug))
-			debug[c] = 1;
-		break;
 
-	case 'o':
-		outfile = ARGF();
-		break;
+	flagfn1("D", "name[=value]: add #define", dodef);
+	flagfn1("I", "dir: add dir to include path", setinclude);
+	flagcount("S", "print assembly and machine code", &debug['S']);
+	flagcount("m", "debug preprocessor macros", &debug['m']);
+	flagstr("o", "file: set output file", &outfile);
+	flagstr("trimpath", "prefix: remove prefix from recorded source file paths", &ctxt->trimpath);
 
-	case 'D':
-		p = ARGF();
-		if(p) {
-			if (nDlist%8 == 0)
-				Dlist = allocn(Dlist, nDlist*sizeof(char *), 
-					8*sizeof(char *));
-			Dlist[nDlist++] = p;
-		}
-		break;
+	flagparse(&argc, &argv, usage);
+	ctxt->debugasm = debug['S'];
 
-	case 'I':
-		p = ARGF();
-		setinclude(p);
-		break;
-
-	case 'S':
-		ctxt->debugasm++;
-		break;
-	} ARGEND
-	if(*argv == 0) {
-		print("usage: %ca [-options] file.s\n", thechar);
-		errorexit();
-	}
+	if(argc < 1)
+		usage();
 	if(argc > 1){
 		print("can't assemble multiple files\n");
 		errorexit();
 	}
+
 	if(assemble(argv[0]))
 		errorexit();
+	Bflush(&bstdout);
 	exits(0);
 }
 
 int
 assemble(char *file)
 {
-	char ofile[100], incfile[20], *p;
+	char *ofile, *p;
 	int i, of;
 
+	ofile = alloc(strlen(file)+3); // +3 for .x\0 (x=thechar)
 	strcpy(ofile, file);
-	if(p = strrchr(ofile, pathchar())) {
+	p = utfrrune(ofile, pathchar());
+	if(p) {
 		include[0] = ofile;
 		*p++ = 0;
 	} else
 		p = ofile;
 	if(outfile == 0) {
 		outfile = p;
-		if(p = strrchr(outfile, '.'))
-			if(p[1] == 's' && p[2] == 0)
-				p[0] = 0;
-		p = strrchr(outfile, 0);
-		p[0] = '.';
-		p[1] = thechar;
-		p[2] = 0;
-	}
-	p = getenv("INCLUDE");
-	if(p) {
-		setinclude(p);
-	} else {
-		if(systemtype(Plan9)) {
-			sprint(incfile,"/%s/include", thestring);
-			setinclude(strdup(incfile));
-		}
+		if(outfile){
+			p = utfrrune(outfile, '.');
+			if(p)
+				if(p[1] == 's' && p[2] == 0)
+					p[0] = 0;
+			p = utfrune(outfile, 0);
+			p[0] = '.';
+			p[1] = thechar;
+			p[2] = 0;
+		} else
+			outfile = "/dev/null";
 	}
 
 	of = create(outfile, OWRITE, 0664);
@@ -166,10 +168,9 @@ assemble(char *file)
 		errorexit();
 	}
 	Binit(&obuf, of, OWRITE);
-	Bprint(&obuf, "go object %s %s %s\n", getgoos(), thestring, getgoversion());
-	Bprint(&obuf, "\n!\n");
+	Bprint(&obuf, "go object %s %s %s\n", getgoos(), getgoarch(), getgoversion());
+	Bprint(&obuf, "!\n");
 
-	pass = 1;
 	for(pass = 1; pass <= 2; pass++) {
 		nosched = 0;
 		pinit(file);