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List:       openjdk-hotspot-runtime-dev
Subject:    Re: RFR: 8297534: Specify the size of MEMFLAGS [v3]
From:       Thomas Stuefe <stuefe () openjdk ! org>
Date:       2022-11-25 13:16:33
Message-ID: 7ktXpvQClrU8ezmSKpjBvdIfYrJazKm3sZOvVZe694Y=.2e1f6038-48cf-4dd6-9dd5-3049e58ea7ba () github ! com
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On Fri, 25 Nov 2022 12:03:48 GMT, Johan Sjölen <jsjolen@openjdk.org> wrote:

> > Hi!
> > 
> > In MallocHeader we assume that MEMFLAGS can be stored in a uint8_t, see:
> > 
> > ```c++
> > class MallocHeader {
> > 
> > NOT_LP64(uint32_t _alt_canary);
> > const size_t _size;
> > const uint32_t _mst_marker;
> > const uint8_t _flags;
> > const uint8_t _unused;
> > uint16_t _canary;
> > // SNIP!
> > inline MEMFLAGS flags() const { return (MEMFLAGS)_flags; }
> > 
> > 
> > With C++11 we can specify the underlying type of an `enum class`, so let's just \
> > do that. If we generate 257 memflags we'll get a compile error. I don't believe \
> > that this would lead to any change in the behavior of the code. 
> > Testing: Compiled the code. Running tier1 testing right now.
> 
> Johan Sjölen has updated the pull request incrementally with one additional commit \
> since the last revision: 
> Add STATIC_ASSERT

Still good.

-------------

PR: https://git.openjdk.org/jdk/pull/11336


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