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)) { > > _________________________________________________ > For list-related administrative tasks: > http://lists.racket-lang.org/listinfo/dev > -- Jay McCarthy <[email protected]> Assistant Professor / Brigham Young University http://faculty.cs.byu.edu/~jay "The glory of God is Intelligence" - D&C 93 _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/dev
