I think this approach makes sense, although there can be two compile buffers, *grep* and *compile*. I tried the patch out, and I seem to get an issue where if I'm not focused on the compile buffer, it will go to the next error once or twice and then say "no more hits" even though the point is only halfway down the buffer.

On Thu, Aug 1, 2024, at 7:09 AM, Omar Polo wrote:
> 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");