From: Stefan Sperling <stsp@stsp.name>
Subject: Re: got rebase or diff library bug
To: Mark Jamsek <mark@jamsek.com>
Cc: Christian Weisgerber <naddy@mips.inka.de>, gameoftrees@openbsd.org
Date: Tue, 6 Aug 2024 08:50:55 +0200

On Mon, Aug 05, 2024 at 10:26:13PM +1000, Mark Jamsek wrote:
> Mark Jamsek <mark@jamsek.com> wrote:
> > Christian Weisgerber <naddy@mips.inka.de> wrote:
> > > Christian Weisgerber:
> > > 
> > > > It also fixes my original problem.  I rebased the llvm18 branch in
> > > > my repository and the GCNRegPressure.cpp file survived unscathed.
> > > 
> > > Wait, no, it gained a trailing '\n':
> > 
> > Thanks, naddy! I was worried about that case.
> > 
> > I'll see if if I can come up with a minimal repro and a proper fix.
> 
> I've not yet managed to produce a minimal reproduction of your llvm case
> such that the trailing newline is appended with the previous diff, but
> I'm pretty sure I know why it's happening: it's because the ed script is
> not necessarily generated in order so we end up unsetting no_eofnl.
> 
> If I'm right, the below diff should now work with your llvm merge and
> it's still working with the simple hello\nworld\n+fubarEOF case.
> 
> Please let me know if GCNRegPressure.cpp still survives your llvm rebase
> unscathed and without gaining the trailing '\n', and I'll keep working
> on a minimal test case for it too. Thanks, naddy!
> 

fix is ok by me, thanks!

> diffstat f997e889eb0517a24a28f2f4000d6915683fef86 de493b727770ab0c07070cc9aff938371f4e4132
>  M  lib/diff3.c  |  17+  0-
> 
> 1 file changed, 17 insertions(+), 0 deletions(-)
> 
> diff f997e889eb0517a24a28f2f4000d6915683fef86 de493b727770ab0c07070cc9aff938371f4e4132
> commit - f997e889eb0517a24a28f2f4000d6915683fef86
> commit + de493b727770ab0c07070cc9aff938371f4e4132
> blob - c1ca2fdf44d461cda6adb950263ed6a9775971ac
> blob + 870a8eac2fb905a8f66de48e38c247aa970d2c5e
> --- lib/diff3.c
> +++ lib/diff3.c
> @@ -155,6 +155,8 @@ struct diff3_state {
>  
>  	char *buf;
>  
> +	int no_eofnl;		/* set if the merged file has no eof newline */
> +
>  	BUF *diffbuf;
>  };
>  
> @@ -417,6 +419,10 @@ out:
>  			err = got_error_from_errno("fclose");
>  	}
>  	if (err == NULL && diffb) {
> +		dlen = buf_len(diffb);
> +		if (d3s->no_eofnl && dlen > 0 &&
> +		    buf_getc(diffb, dlen - 1) == '\n')
> +			--diffb->cb_len;
>  		if (buf_write_fd(diffb, outfd) < 0)
>  			err = got_error_from_errno("buf_write_fd");
>  		*overlapcnt = d3s->overlapcnt;
> @@ -1063,6 +1069,17 @@ edscript(int n, struct diff3_state *d3s)
>  		}
>  
>  		if (!d3s->overlap[n]) {
> +			size_t len;
> +
> +			len = buf_len(d3s->diffbuf);
> +			if (len > 0) {
> +				if (buf_getc(d3s->diffbuf, len - 1) != '\n') {
> +					err = buf_putc(d3s->diffbuf, '\n');
> +					if (err != NULL)
> +						goto done;
> +					d3s->no_eofnl = 1;
> +				}
> +			}
>  			err = diff_output(d3s->diffbuf, ".\n");
>  			if (err)
>  				goto done;
> 
> 
> -- 
> Mark Jamsek <https://bsdbox.org>
> GPG: F2FF 13DE 6A06 C471 CA80  E6E2 2930 DC66 86EE CF68
> 
>