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Re: [PATCH 1/2] avoid shifting signed integers 31 bits

From
Duy Nguyen <pclouds@gmail.com>
Date
Dec 31, 2015, 05:10 UTC
Message-ID
<CACsJy8CAAqZFQCfadUov7DFhSgh=dtGfE-onbXZQXO-0Y2652g@mail.gmail.com>
In-Reply-To
<20151229063545.GA30340@sigill.intra.peff.net>
On Tue, Dec 29, 2015 at 1:35 PM, Jeff King <peff@peff.net> wrote:
Show 7 quoted lines
> We sometimes use 32-bit unsigned integers as bit-fields.
> It's fine to access the MSB, because it's unsigned. However,
> doing so as "1 << 31" is wrong, because the constant "1" is
> a signed int, and we shift into the sign bit, causing
> undefined behavior.
>
> We can fix this by using "1U" as the constant.
We have this in cache.h, should it be fixed as well?

/* CE_EXTENDED2 is for future extension */ #define CE_EXTENDED2 (1 << 31)

-- 
Duy
Previous: Jeff KingNext: Jeff King
Message 5 of 12 in “compiling with -fsanitize=undefined”
  1. 0/2 compiling with -fsanitize=undefinedJeff King, Dec 29, 2015
  2. 1/2 avoid shifting signed integers 31 bitsJeff King, Dec 29, 2015
  3. Junio C HamanoDec 30, 2015
  4. Jeff KingDec 30, 2015
  5. Duy NguyenDec 31, 2015
  6. Jeff KingDec 31, 2015
  7. Junio C HamanoJan 4, 2016
  8. Jeff KingJan 4, 2016
  9. 2/2 bswap: add NO_UNALIGNED_LOADS defineJeff King, Dec 29, 2015
  10. Eric SunshineDec 29, 2015
  11. Jeff KingDec 29, 2015
  12. Jeff KingDec 29, 2015

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