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| author | Thiago Macieira <thiago.macieira@intel.com> | 2017-10-21 11:24:54 -0700 |
|---|---|---|
| committer | Thiago Macieira <thiago.macieira@intel.com> | 2017-11-20 15:49:36 +0000 |
| commit | 3c7a6a7a581f9ea6f05a22a912d660c5402a1fa8 (patch) | |
| tree | 2dfc0d1c7ecc59fab766a972c8aa694b2ba3a3d5 /src/corelib/global | |
| parent | bb3872d60975724a50ff910b6dd108d1944db597 (diff) | |
QRandomGenerator: Enforce the use of 32-bit integers in the engine
std::mt19937 is defined as operating on uint_fast32_t, which is usually
just a 32-bit integer. That's not the case on 64-bit Linux, where it is
actually 64-bit wide, meaning sizeof(std::mt19937) jumps from 2504 to
5000 bytes, with exactly 50% of it filled with zeroes. The seed()
function also needs a large zero-extending loop.
Change-Id: Icaa86fc7b54d4b368c0efffd14efa911e2a40b44
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Diffstat (limited to 'src/corelib/global')
| -rw-r--r-- | src/corelib/global/qrandom.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/src/corelib/global/qrandom.h b/src/corelib/global/qrandom.h index bde64646a4..005de0941f 100644 --- a/src/corelib/global/qrandom.h +++ b/src/corelib/global/qrandom.h @@ -177,7 +177,8 @@ private: friend class QRandomGenerator64; struct SystemGenerator; struct SystemAndGlobalGenerators; - typedef std::mt19937 RandomEngine; + using RandomEngine = std::mersenne_twister_engine<quint32, + 32,624,397,31,0x9908b0df,11,0xffffffff,7,0x9d2c5680,15,0xefc60000,18,1812433253>; union Storage { uint dummy; |