From 436728fe9d75d05fa2439f867ca2039012b86e69 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Thu, 3 Oct 2024 17:09:24 -0400 Subject: [PATCH] diff: return const char from output_prefix callback The diff_options structure has an output_prefix callback for returning a prefix string, but it does so by returning a pointer to a strbuf. This makes the interface awkward. There's no reason the callback should need to use a strbuf, and it creates questions about whether the ownership of the resulting buffer should be transferred to the caller (it should not be, but a recent attempt to clean up this code led to a double-free in some cases). The one advantage we get is that the strbuf contains a ptr/len pair, so we could in theory have a prefix with embedded NULs. But we can observe that none of the existing callbacks would ever produce such a NUL (they are usually just indentation or graph symbols, and even the "--line-prefix" option takes a NUL-terminated string). And anyway, only one caller (the one in log_tree_diff_flush) actually looks at the strbuf length. In every other case we use a helper function which discards the length and just returns the NUL-terminated string. So let's just have the callback return a "const char *" pointer. It's up to the callbacks themselves if they want to use a strbuf under the hood. And now the caller in log_tree_diff_flush() can just use the helper function along with everybody else. That lets us even simplify out the function pointer check, since the helper returns an empty string (technically this does mean we'll sometimes issue an empty fputs() call, but I don't think this code path is hot enough to care about that). Signed-off-by: Jeff King Signed-off-by: Junio C Hamano --- diff-lib.c | 4 ++-- diff.c | 9 +++------ diff.h | 2 +- graph.c | 4 ++-- log-tree.c | 7 +------ range-diff.c | 4 ++-- 6 files changed, 11 insertions(+), 19 deletions(-) diff --git a/diff-lib.c b/diff-lib.c index 7a1eb63757..1cbf983a9c 100644 --- a/diff-lib.c +++ b/diff-lib.c @@ -704,7 +704,7 @@ int index_differs_from(struct repository *r, return (has_changes != 0); } -static struct strbuf *idiff_prefix_cb(struct diff_options *opt UNUSED, void *data) +static const char *idiff_prefix_cb(struct diff_options *opt UNUSED, void *data) { return data; } @@ -719,7 +719,7 @@ void show_interdiff(const struct object_id *oid1, const struct object_id *oid2, opts.output_format = DIFF_FORMAT_PATCH; opts.output_prefix = idiff_prefix_cb; strbuf_addchars(&prefix, ' ', indent); - opts.output_prefix_data = &prefix; + opts.output_prefix_data = prefix.buf; diff_setup_done(&opts); diff_tree_oid(oid1, oid2, "", &opts); diff --git a/diff.c b/diff.c index f725d217de..a7bfe73fe6 100644 --- a/diff.c +++ b/diff.c @@ -2313,12 +2313,9 @@ const char *diff_get_color(int diff_use_color, enum color_diff ix) const char *diff_line_prefix(struct diff_options *opt) { - struct strbuf *msgbuf; - if (!opt->output_prefix) - return ""; - - msgbuf = opt->output_prefix(opt, opt->output_prefix_data); - return msgbuf->buf; + return opt->output_prefix ? + opt->output_prefix(opt, opt->output_prefix_data) : + ""; } static unsigned long sane_truncate_line(char *line, unsigned long len) diff --git a/diff.h b/diff.h index f816d3b12b..ed91c92e3a 100644 --- a/diff.h +++ b/diff.h @@ -94,7 +94,7 @@ typedef void (*add_remove_fn_t)(struct diff_options *options, typedef void (*diff_format_fn_t)(struct diff_queue_struct *q, struct diff_options *options, void *data); -typedef struct strbuf *(*diff_prefix_fn_t)(struct diff_options *opt, void *data); +typedef const char *(*diff_prefix_fn_t)(struct diff_options *opt, void *data); #define DIFF_FORMAT_RAW 0x0001 #define DIFF_FORMAT_DIFFSTAT 0x0002 diff --git a/graph.c b/graph.c index 34b18a80d4..6a4db229bb 100644 --- a/graph.c +++ b/graph.c @@ -309,7 +309,7 @@ struct git_graph { unsigned short default_column_color; }; -static struct strbuf *diff_output_prefix_callback(struct diff_options *opt, void *data) +static const char *diff_output_prefix_callback(struct diff_options *opt, void *data) { struct git_graph *graph = data; static struct strbuf msgbuf = STRBUF_INIT; @@ -321,7 +321,7 @@ static struct strbuf *diff_output_prefix_callback(struct diff_options *opt, void strbuf_addstr(&msgbuf, opt->line_prefix); if (graph) graph_padding_line(graph, &msgbuf); - return &msgbuf; + return msgbuf.buf; } static const struct diff_options *default_diffopt; diff --git a/log-tree.c b/log-tree.c index 13524bc888..7a5828ce63 100644 --- a/log-tree.c +++ b/log-tree.c @@ -922,12 +922,7 @@ int log_tree_diff_flush(struct rev_info *opt) * diff/diffstat output for readability. */ int pch = DIFF_FORMAT_DIFFSTAT | DIFF_FORMAT_PATCH; - if (opt->diffopt.output_prefix) { - struct strbuf *msg = NULL; - msg = opt->diffopt.output_prefix(&opt->diffopt, - opt->diffopt.output_prefix_data); - fwrite(msg->buf, msg->len, 1, opt->diffopt.file); - } + fputs(diff_line_prefix(&opt->diffopt), opt->diffopt.file); /* * We may have shown three-dashes line early diff --git a/range-diff.c b/range-diff.c index 5f01605550..f28a388fb8 100644 --- a/range-diff.c +++ b/range-diff.c @@ -478,7 +478,7 @@ static void patch_diff(const char *a, const char *b, diff_flush(diffopt); } -static struct strbuf *output_prefix_cb(struct diff_options *opt UNUSED, void *data) +static const char *output_prefix_cb(struct diff_options *opt UNUSED, void *data) { return data; } @@ -506,7 +506,7 @@ static void output(struct string_list *a, struct string_list *b, opts.flags.suppress_hunk_header_line_count = 1; opts.output_prefix = output_prefix_cb; strbuf_addstr(&indent, " "); - opts.output_prefix_data = &indent; + opts.output_prefix_data = indent.buf; diff_setup_done(&opts); /*