improved (plumb(1)'able) error messages from lex(1).

Reference: /n/sources/patch/applied/lex-err-msgs
Date: Wed Dec 17 17:32:52 CET 2008
Signed-off-by: steve@quintile.net

--- /sys/src/cmd/lex/lmain.c	Wed Dec 17 17:31:34 2008
+++ /sys/src/cmd/lex/lmain.c	Wed Dec 17 17:31:31 2008
@@ -32,6 +32,7 @@
 char **sargv;
 uchar buf[520];
 int yyline;		/* line number of file */
+char *yyfile;		/* filename for error messages */
 int eof;
 int lgatflg;
 int divflg;
@@ -119,13 +120,15 @@
 	sargc = argc;
 	sargv = argv;
 	if (argc > 0){
-		fin = Bopen(argv[fptr++], OREAD);
+		yyfile = argv[fptr++];
+		fin = Bopen(yyfile, OREAD);
 		if(fin == 0)
-			error ("Can't read input file %s",argv[0]);
+			error ("%s - can't open file", yyfile);
 		sargc--;
 		sargv++;
 	}
 	else {
+		yyfile = "stdin";
 		fin = myalloc(sizeof(Biobuf), 1);
 		if(fin == 0)
 			exits("core");
@@ -289,5 +292,5 @@
 void
 yyerror(char *s)
 {
-	fprint(2, "line %d: %s\n", yyline, s);
+	fprint(2, "%s:%d %s\n", yyfile, yyline, s);
 }
--- /sys/src/cmd/lex/ldefs.h	Wed Dec 17 17:31:41 2008
+++ /sys/src/cmd/lex/ldefs.h	Wed Dec 17 17:31:37 2008
@@ -68,6 +68,7 @@
 extern char **sargv;
 extern uchar buf[520];
 extern int yyline;		/* line number of file */
+extern char *yyfile;		/* file name of file */
 extern int sect;
 extern int eof;
 extern int lgatflg;
--- /sys/src/cmd/lex/sub1.c	Wed Dec 17 17:31:48 2008
+++ /sys/src/cmd/lex/sub1.c	Wed Dec 17 17:31:44 2008
@@ -21,7 +21,7 @@
 {
 	char buf[1024];
 
-	if(!eof)fprint(errorf,"%d: ",yyline);
+	if(!eof)fprint(errorf,"%s:%d  ", yyfile, yyline);
 	fprint(errorf,"(%s) ", type);
 	vseprint(buf, buf+sizeof(buf), fmt, argl);
 	fprint(errorf, "%s\n", buf);
@@ -174,10 +174,12 @@
 { /* copy C action to the next ; or closing } */
 	int brac, c, mth;
 	int savline, sw;
+	char *savfile;
 
 	brac = 0;
 	sw = TRUE;
 	savline = 0;
+	savfile = "?";
 
 while(!eof){
 	c = gch();
@@ -201,6 +203,7 @@
 case '{':
 		brac++;
 		savline=yyline;
+		savfile=yyfile;
 		break;
 
 case '}':
@@ -221,6 +224,7 @@
 
 		Bputc(&fout, c);
 		savline=yyline;
+		savfile=yyfile;
 		while( c=gch() ){
 			if( c=='*' ){
 				Bputc(&fout, c);
@@ -229,6 +233,7 @@
 			Bputc(&fout, c);
 		}
 		yyline=savline;
+		yyfile=savfile;
 		error( "EOF inside comment" );
 
 case '\'':	/* character constant */
@@ -257,6 +262,7 @@
 
 case '\0':
 		yyline = savline;
+		yyfile = savfile;
 		error("Action does not terminate");
 default:
 		break;		/* usual character */
@@ -277,9 +283,10 @@
 	peek = pushptr > pushc ? *--pushptr : Bgetc(fin);
 	if(peek == Beof && sargc > 1){
 		Bterm(fin);
-		fin = Bopen(sargv[fptr++],OREAD);
+		yyfile = sargv[fptr++];
+		fin = Bopen(yyfile,OREAD);
 		if(fin == 0)
-			error("Cannot open file %s",sargv[fptr-1]);
+			error("%s - cannot open file",yyfile);
 		peek = Bgetc(fin);
 		sargc--;
 		sargv++;