Re: [PATCH v3] log --graph: customize the graph lines with config log.graphColors

On Sun, Jan 08, 2017 at 07:05:12PM -0800, Junio C Hamano wrote:

quoted

+{
+	static char **colors;
+	static int colors_max, colors_alloc;
+	char *string = NULL;
+	const char *end, *start;
+	int i;
+
+	for (i = 0; i < colors_max; i++)
+		free(colors[i]);
+	if (colors)
+		free(colors[colors_max]);
+	colors_max = 0;

The correctness of the first loop relies on the fact that colors is
non-null when colors_max is not zero, and then the freeing of the
colors relies on something else.  It is not wrong per-se, but it
will reduce the "Huh?" factor if you wrote it like so:

	if (colors) {
        	/* 
                 * Reinitialize, but keep the colors[] array.
		 * Note that the last entry is allocated for
		 * reset but colors_max does not count it, hence
		 * "i <= colors_max", not "i < colors_max".
		 */
		int i;
		for (i = 0; i <= colors_max; i++)
			free(colors[i]);
		colors_max = 0;
	}

Yeah, I agree that what you've written here is less confusing. Less
confusing still would be to keep colors_nr, and deal separately with the
"max" interface to graph_set_column_colors().

I also wonder if it is worth just using argv_array. We do not care about
NULL-terminating the list here, but it actually works pretty well as a
generic string-array class (and keeping a NULL at the end of any
array-of-pointers is a reasonable defensive measure). Then the function
becomes:

  argv_array_clear(&colors);
  ...
  if (!color_parse_mem(..., color))
          argv_array_push(&colors, color);
  ...
  argv_array_push(&colors, GIT_COLOR_RESET);
  /* graph_set_column_colors takes a max-index, not a count */
  graph_set_column_colors(colors.argv, colors.argc - 1);

It is not much shorter than ALLOC_GROW(), but IMHO it is easier to read.

-Peff