Re: [PATCH v3] MSVC: fix t0040-parse-options crash

[Junio C Hamano <gitster@pobox.com>]

Marat Radchenko <marat@slonopotamus.org> writes:

> On 64-bit MSVC, pointers are 64 bit but `long` is only 32.
> Thus, casting string to `unsigned long`, which is redundand on other
> platforms, throws away important bits and when later cast to `intptr_t`
> results in corrupt pointer.
>
> This patch fixes test-parse-options by replacing harming cast with
> correct one.
>
> Signed-off-by: Marat Radchenko <marat@slonopotamus.org>
> ---
>
> Aargh! Didn't notice that V2 introduced compilation warning. Take three.

I am glad that I asked you to clarify, as I totally forgot that
there are L32P64 boxes.

I love it every time to see an attempt to describe why the solution
works clearly results in a better patch.  It is not about writing
verbose log message; it is about thinking things through and clearly
cut to the core of the issue.  Moving the string literal to a
separate variable to be used in the constructor in v1 was totally a
red-herring.  Your updated log message makes it crystal clear that
using the correct typecast, not "unsigned long" but "intptr_t", is
the core of the solution.

As OPT_SET_PTR() is about setting the pointer value to intptr_t defval,
a follow-up patch on top of this fix (see attached) may not be a bad
thing to have, but that patch alone will not fix this issue without
dropping the unneeded and unwanted cast to unsigned long.

Thanks.

>  test-parse-options.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/test-parse-options.c b/test-parse-options.c
> index 434e8b8..6f6c656 100644
> --- a/test-parse-options.c
> +++ b/test-parse-options.c
> @@ -60,7 +60,7 @@ int main(int argc, char **argv)
>  		OPT_STRING('o', NULL, &string, "str", "get another string"),
>  		OPT_NOOP_NOARG(0, "obsolete"),
>  		OPT_SET_PTR(0, "default-string", &string,
> -			"set string to default", (unsigned long)"default"),
> +			"set string to default", (intptr_t)"default"),
>  		OPT_STRING_LIST(0, "list", &list, "str", "add str to list"),
>  		OPT_GROUP("Magic arguments"),
>  		OPT_ARGUMENT("quux", "means --quux"),


 parse-options.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/parse-options.h b/parse-options.h
index d670cb9..7a24d2e 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -129,7 +129,7 @@ struct option {
 #define OPT_HIDDEN_BOOL(s, l, v, h) { OPTION_SET_INT, (s), (l), (v), NULL, \
 				      (h), PARSE_OPT_NOARG | PARSE_OPT_HIDDEN, NULL, 1}
 #define OPT_SET_PTR(s, l, v, h, p)  { OPTION_SET_PTR, (s), (l), (v), NULL, \
-				      (h), PARSE_OPT_NOARG, NULL, (p) }
+				      (h), PARSE_OPT_NOARG, NULL, (intptr_t)(p) }
 #define OPT_CMDMODE(s, l, v, h, i) { OPTION_CMDMODE, (s), (l), (v), NULL, \
 				      (h), PARSE_OPT_NOARG|PARSE_OPT_NONEG, NULL, (i) }
 #define OPT_INTEGER(s, l, v, h)     { OPTION_INTEGER, (s), (l), (v), N_("n"), (h) }