0-length arrays in Buddy ranges #672
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This fixes the 0-length arrays discussed (and made into assertion failures) in the next commit. This works because the Buddy's `MIN_SIZE_BITS` is instantiated at `MIN_CHUNK_BITS`, and so we ensure that we instantiate the LargeBuddyRange only with `max_page_chunk_size_bits` above `MIN_CHUNK_BITS`.
Now that the case leading to several 0-sized arrays in Buddy ranges, that then cause gcc's -Warray-bounds to trip, has been removed, add a static assert so that we can catch this with better error messages next time.
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You OK to merge even though macos CI is still pending? |
Yeah. I think Mac os 11 support has been removed. I think we need to remove and possibly add the next version |
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Buddyranges can be instantiated withMAX_SIZE_BITS == MIN_SIZE_BITS(or, in principle,<=). If this happens, the resulting class will contain 0-length arrays, and code that appears to attempt to access an element therein trips gcc's-Warray-bounds.This PR contains two commits: one that adds a
static_assertto ensure thatBuddy's arrays are always of positive size, and one possible way to fix the case I'm tripping over. The latter works because the Buddy'sMIN_SIZE_BITSis instantiated atMIN_CHUNK_BITS, and so the change herein then ensures that itsMAX_SIZE_BITSis strictly greater thanMIN_CHUNK_BITS.A different, and possibly better, solution would be to drop the
LargeBuddyRangefromCentralMetaRangewhenmax_page_chunk_size_bitsis computed to be equal toMIN_CHUNK_BITS.Please advise.