From: Omar Polo <op@omarpolo.com>
Subject: Re: mg: prevet crash with invalid compile buffer
To: Dante Catalfamo <dante@lambda.cx>
Cc: tech@openbsd.org
Date: Thu, 01 Aug 2024 13:09:03 +0200

On 2024/07/31 13:06:50 -0400, "Dante Catalfamo" <dante@lambda.cx> wrote:
> Realized I could open the compile buffer in a new window if it's not associated with one currently.

counter-proposal: if, instead of trying to maintain the global pointers
that can get invalidated by kill-buffer, in next_error we just search
for a buffer in the compile-mode and use it?  mg has only one compile
buffer anyway.

I don't use often M-x compile or grep, but with some light testing this
works for me.  (actually i should resurrect your other diff to jump
between hits in the compile buffer and my old diff for M-x grep.)

what do you think?


diff /home/op/w/mg
commit - 80617155f9fa32a62f9dbcbea7b90ebbdb39ec14
path + /home/op/w/mg
blob - aa7f9dfd87d387253c9d8f8b20b0f47f5589b6fe
file + grep.c
--- grep.c
+++ grep.c
@@ -29,14 +29,6 @@ void grep_init(void);
 
 static char compile_last_command[NFILEN] = "make ";
 
-/*
- * Hints for next-error
- *
- * XXX - need some kind of callback to find out when those get killed.
- */
-struct mgwin	*compile_win;
-struct buffer	*compile_buffer;
-
 static PF compile_pf[] = {
 	compile_goto_error
 };
@@ -82,7 +74,7 @@ grep(int f, int n)
 	if ((wp = popbuf(bp, WNONE)) == NULL)
 		return (FALSE);
 	curbp = bp;
-	compile_win = curwp = wp;
+	curwp = wp;
 	return (TRUE);
 }
 
@@ -108,7 +100,7 @@ compile(int f, int n)
 	if ((wp = popbuf(bp, WNONE)) == NULL)
 		return (FALSE);
 	curbp = bp;
-	compile_win = curwp = wp;
+	curwp = wp;
 	gotoline(FFARG, 0);
 	return (TRUE);
 }
@@ -166,7 +158,7 @@ gid(int f, int n)
 	if ((wp = popbuf(bp, WNONE)) == NULL)
 		return (FALSE);
 	curbp = bp;
-	compile_win = curwp = wp;
+	curwp = wp;
 	return (TRUE);
 }
 
@@ -240,8 +232,6 @@ compile_mode(const char *name, const char *command)
 	bp->b_modes[1] = name_mode("compile");
 	bp->b_nmodes = 1;
 
-	compile_buffer = bp;
-
 	if (chdir(cwd) == -1) {
 		dobeep();
 		ewprintf("Can't change dir back to %s", cwd);
@@ -261,9 +251,7 @@ compile_goto_error(int f, int n)
 	const char *errstr;
 	struct line	*last;
 
-	compile_win = curwp;
-	compile_buffer = curbp;
-	last = blastlp(compile_buffer);
+	last = blastlp(curbp);
 
  retry:
 	/* last line is compilation result */
@@ -317,16 +305,42 @@ fail:
 	return (FALSE);
 }
 
+static int
+show_compile_buffer(void)
+{
+	struct mgwin	*wp;
+	struct buffer	*bp;
+	int		 i;
+
+	for (bp = bheadp; bp != NULL; bp = bp->b_bufp) {
+		for (i = 0; i <= bp->b_nmodes; ++i)
+			if (!strcmp(bp->b_modes[i]->p_name, "compile"))
+				goto done;
+	}
+ done:
+	if (bp == NULL)
+		return (FALSE);
+
+	for (wp = wheadp; wp != NULL; wp = wp->w_wndp) {
+		if (wp->w_bufp == bp)
+			return (TRUE);
+	}
+
+	if (splitwind(0, 1) == FALSE ||
+	    showbuffer(bp, curwp, 0) == FALSE)
+		return (FALSE);
+
+	return (TRUE);
+}
+
 int
 next_error(int f, int n)
 {
-	if (compile_win == NULL || compile_buffer == NULL) {
+	if (show_compile_buffer() == FALSE) {
 		dobeep();
 		ewprintf("No compilation active");
 		return (FALSE);
 	}
-	curwp = compile_win;
-	curbp = compile_buffer;
 	if (curwp->w_dotp == blastlp(curbp)) {
 		dobeep();
 		ewprintf("No more hits");