Oh sorry, I meant how did the bug manifest itself in racket programs.
On 08/16/2011 11:02 AM, Jay McCarthy wrote:
> The C macro expanded into more than a single expression, but there was
> no {} after the else, so the latter expressions always ran.
>
> This is a great example :)
>
> Jay
>
> On Tue, Aug 16, 2011 at 11:00 AM, Jon Rafkind <[email protected]> wrote:
>> What was the bug? :)
>>
>> On 08/16/2011 10:43 AM, [email protected] wrote:
>>> mflatt has updated `master' from d05f138ed2 to 311d55b5cf.
>>> http://git.racket-lang.org/plt/d05f138ed2..311d55b5cf
>>>
>>> =====[ 1 Commits ]======================================================
>>>
>>> Directory summary:
>>> 100.0% src/racket/src/
>>>
>>> ~~~~~~~~~~
>>>
>>> 311d55b Matthew Flatt <[email protected]> 2011-08-16 10:27
>>> :
>>> | fix bug that affects `free-identifier=?'
>>> |
>>> | This bug is in the "amazing that it lurked for years" category,
>>> | as well as the "stupid use of C preprocessor" category.
>>> :
>>> M src/racket/src/syntax.c | 5 +++--
>>>
>>> =====[ Overall Diff ]===================================================
>>>
>>> src/racket/src/syntax.c
>>> ~~~~~~~~~~~~~~~~~~~~~~~
>>> --- OLD/src/racket/src/syntax.c
>>> +++ NEW/src/racket/src/syntax.c
>>> @@ -365,7 +365,7 @@ XFORM_NONGCING static MZ_INLINE void
>>> DO_WRAP_POS_INC(Wrap_Pos *w)
>>> #define WRAP_POS_INIT_END(w) (w.l = scheme_null, w.a = NULL, w.is_limb =
>>> 0, w.pos = 0)
>>> #define WRAP_POS_END_P(w) SCHEME_NULLP(w.l)
>>> #define WRAP_POS_FIRST(w) w.a
>>> -#define WRAP_POS_COPY(w, w2) w.l = (w2).l; w.a = (w2).a; w.is_limb=
>>> (w2).is_limb; w.pos = (w2).pos
>>> +#define WRAP_POS_COPY(w, w2) w.l = (w2).l; w.a = (w2).a; w.is_limb =
>>> (w2).is_limb; w.pos = (w2).pos
>>>
>>> /* Walking backwards through one chunk: */
>>>
>>> @@ -3618,8 +3618,9 @@ static Scheme_Object *resolve_env(WRAP_POS *_wraps,
>>> if (_wraps) {
>>> WRAP_POS_COPY(wraps, *_wraps);
>>> WRAP_POS_INC(wraps);
>>> - } else
>>> + } else {
>>> WRAP_POS_INIT(wraps, ((Scheme_Stx *)a)->wraps);
>>> + }
>>>
>>> while (1) {
>>> if (WRAP_POS_END_P(wraps)) {
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