diff --git a/rts/Sparks.c b/rts/Sparks.c index 571529afbbc31b6f8d7c2e366f4b7635b754dde2..9e4492ac1925c66b4fe942d8a6480671200d4aac 100644 --- a/rts/Sparks.c +++ b/rts/Sparks.c @@ -208,7 +208,9 @@ steal(SparkPool *deque) b = deque->bottom; t = deque->top; - if (b - t <= 0 ) { + // NB. b and t are unsigned; we need a signed value for the test + // below. + if ((long)b - (long)t <= 0 ) { return NULL; /* already looks empty, abort */ } @@ -259,7 +261,7 @@ looksEmpty(SparkPool* deque) StgWord t = deque->top; StgWord b = deque->bottom; /* try to prefer false negatives by reading top first */ - return (b - t <= 0); + return ((long)b - (long)t <= 0); /* => array is *never* completely filled, always 1 place free! */ } @@ -304,7 +306,10 @@ pushBottom (SparkPool* deque, StgClosurePtr elem) This is why we do not just call empty(deque) here. */ t = deque->topBound; - if ( b - t >= sz ) { /* nota bene: sz == deque->size - 1, thus ">=" */ + if ( (StgInt)b - (StgInt)t >= (StgInt)sz ) { + /* NB. 1. sz == deque->size - 1, thus ">=" + 2. signed comparison, it is possible that t > b + */ /* could be full, check the real top value in this case */ t = deque->top; deque->topBound = t;