Re: [PATCH] Reserve a slot for argv[0] in default_arg.

From: Petter Urkedal <urkedal@nbi.dk>
Date: Oct 4, 2009, 14:51 UTC
Message-ID: <20091004145141.GA16477@eideticdew.org>
In-Reply-To: <20091004133333.GA13894@sigill.intra.peff.net>

On 2009-10-04, Jeff King wrote:

> Thanks, your fix looks sane. But I am curious about whether we are
> triggering some glibc pickiness that is in your setup, or if we are
> somehow violating the assumption that we only ever look at
> default_arg[1] and beyond.

I had a look at parse-options.c. In parse_options_start, argv is assigned to ctx->out, which is overwritten from index 0 in parse_options_end. This will show the problem:

diff --git a/builtin-show-branch.c b/builtin-show-branch.c
index 3510a86..1c587ad 100644
--- a/builtin-show-branch.c
+++ b/builtin-show-branch.c
@@ -691,6 +691,7 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
                showbranch_use_color = git_use_color_default;
 
        /* If nothing is specified, try the default first */
+       printf("default_arg = %p\n", default_arg);
        if (ac == 1 && default_num) {
                ac = default_num + 1;
                av = default_arg - 1; /* ick; we would not address av[0] */
diff --git a/parse-options.c b/parse-options.c
index f559411..267e752 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -435,6 +435,7 @@ unknown:
 
 int parse_options_end(struct parse_opt_ctx_t *ctx)
 {
+       printf("Assigning to %p\n", ctx->out + ctx->cpidx);
        memmove(ctx->out + ctx->cpidx, ctx->argv, ctx->argc * sizeof(*ctx->out));
        ctx->out[ctx->cpidx + ctx->argc] = NULL;
        return ctx->cpidx + ctx->argc;