Hi Junio,
---- On Thu, 06 Nov 2025 00:57:27 +0800 Junio C Hamano <gitster@pobox.com> wrote ---
> Li Chen <me@linux.beauty> writes:
>
> > From: Li Chen <chenl311@chinatelecom.cn>
> >
> > Extracted trailer processing into a helper that accumulates output in
> > a strbuf before writing.
> >
> > Updated interpret_trailers() to reuse the helper, buffer output, and
> > clean up both input and output buffers after writing.
>
> Imperative?
>
> >
> > Signed-off-by: Li Chen <chenl311@chinatelecom.cn>
> > ---
> > builtin/interpret-trailers.c | 51 ++++++++++++++++++++----------------
> > 1 file changed, 29 insertions(+), 22 deletions(-)
> >
> > diff --git a/builtin/interpret-trailers.c b/builtin/interpret-trailers.c
> > index 41b0750e5a..4c90580fff 100644
> > --- a/builtin/interpret-trailers.c
> > +++ b/builtin/interpret-trailers.c
> > @@ -136,32 +136,21 @@ static void read_input_file(struct strbuf *sb, const char *file)
> > strbuf_complete_line(sb);
> > }
> >
> > -static void interpret_trailers(const struct process_trailer_options *opts,
> > - struct list_head *new_trailer_head,
> > - const char *file)
> > +static void process_trailers(const struct process_trailer_options *opts,
> > + struct list_head *new_trailer_head,
> > + struct strbuf *sb, struct strbuf *out)
>
> So we gained *out strbuf; in the preimage below I see fwrite(),
> fprintf(), etc. to outfile that is either stdout or tempfile, but
> presumably the output all will be captured in the strbuf instead,
> which makes sense. It is a bit curious what the new paramater sb
> is, but this is a file-scope static helper, so it does not strictly
> require documenting. Having a comment would still be nicer, though,
> unlike "struct process_trailer_options" that is very limited
> purpose, "strbuf" can be used for any string processing, so a good
> variable name like "out" that conveys what it is used for by
> implication is good, but "sb", which is obvious abbreviation for
> "Str Buf", conveys no useful information.
Thanks, I would rename the variable in next version.
>
> > {
> > LIST_HEAD(head);
> > - struct strbuf sb = STRBUF_INIT;
> > - struct strbuf trailer_block_sb = STRBUF_INIT;
>
> We no longer need a separate strbuf only for trailer block; we will
> see why before we read through this helper function, hopefully.
>
> > struct trailer_block *trailer_block;
> > - FILE *outfile = stdout;
> > -
> > - trailer_config_init();
> >
> > - read_input_file(&sb, file);
> > -
> > - if (opts->in_place)
> > - outfile = create_in_place_tempfile(file);
>
> OK, so the original code read the input (either "file", or standard
> input) into a tempfile and prepared the output file stream.
> Presumably it is now the responsibility of the caller of this new
> function. Initializing the trailer configuration is also what the
> caller of this function is reponsible for, as well.
>
> So this answers one of the questions I had upon starting to read
> this function, i.e. "what is sb?" It holds the input string, which
> is what? Something that look like a commit message that has title,
> body and then a trailer block? We may want to give the parameter a
> better name? I dunno (as this is file-scope static, as long as it
> is obvious to the local caller, it may be OK, but on the other hand,
> the caller needs to differenciate two strbuf parameters to the
> helper function, one used for input and the other output, so if you
> are calling the latter "out", perhaps you would want to call it
> "in", or "input", perhaps?)Yes, in is a better name.
>
> > - trailer_block = parse_trailers(opts, sb.buf, &head);
> > + trailer_block = parse_trailers(opts, sb->buf, &head);
>
> So we parse existing trailers from the input strbuf that is supplied
> by the caller. The rest of this hunk is rewriting FILE* I/O with
> strbuf addition.
>
> > @@ -173,22 +162,40 @@ static void interpret_trailers(const struct process_trailer_options *opts,
> > }
> >
> > /* Print trailer block. */
> > - format_trailers(opts, &head, &trailer_block_sb);
> > + format_trailers(opts, &head, out);
> > free_trailers(&head);
> > - fwrite(trailer_block_sb.buf, 1, trailer_block_sb.len, outfile);
> > - strbuf_release(&trailer_block_sb);
>
> The format_trailers() helper function appends appends to the strbuf
> that is given to it, so instead of using an extra strbuf (and then
> appending that to the output), we just pass our output strbuf to it,
> which is why we no longer need the trailer_block_sb strbuf anymore.
> Makes sense.
>
> > /* Print the lines after the trailer block as is. */
> > if (!opts->only_trailers)
> > - fwrite(sb.buf + trailer_block_end(trailer_block), 1,
> > - sb.len - trailer_block_end(trailer_block), outfile);
> > + strbuf_add(out, sb->buf + trailer_block_end(trailer_block),
> > + sb->len - trailer_block_end(trailer_block));
> > trailer_block_release(trailer_block);
> > +}
>
> And again, FILE* I/O is replaced with appending to the output strbuf
> in the rest of this helper function. Good.
>
> > +static void interpret_trailers(const struct process_trailer_options *opts,
> > + struct list_head *new_trailer_head,
> > + const char *file)
>
> So the original caller of interpret_trailers() now call this outer
> shell, which has the same name and the same function signature as
> the original. Our new process_trailers() helper assumes a handful
> of preparatory steps are already done by the caller, so what we are
> going read here will be mostly those preparation, a call to our new
> helper, and then printing the result to "file" or standard output.
>
> > +{
> > + struct strbuf sb = STRBUF_INIT;
> > + struct strbuf out = STRBUF_INIT;
> > + FILE *outfile = stdout;
> > +
> > + trailer_config_init();
> > +
> > + read_input_file(&sb, file);
> > + if (opts->in_place)
> > + outfile = create_in_place_tempfile(file);
>
> And these are exactly the lines we lost from the new helper.
> Looking good.
>
> > + process_trailers(opts, new_trailer_head, &sb, &out);
>
> And our call. "out" should have what we wanted to output to
> outfile, so ...
>
> > + fwrite(out.buf, out.len, 1, outfile);
>
> ... we write it out. Good. For a single long string that can never
> have NUL in it, I'd personally find it more natural to call fputs(),
> though. Use of fwrite() makes readers unnecessarily wonder if there
> is something unusual (like needing to be able to handle NULs in the
> buffer).
>
> > if (opts->in_place)
> > if (rename_tempfile(&trailers_tempfile, file))
> > die_errno(_("could not rename temporary file to %s"), file);
> >
> > strbuf_release(&sb);
> > + strbuf_release(&out);
>
> OK. We could release out a bit earlier, immediately after fwrite().
>
> Looking mostly good.
>
> > }
> >
> > int cmd_interpret_trailers(int argc,
> Regards,
Li
Li Chen <me@linux.beauty>