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<p class="MsoNormal"><span style="color:#1F497D">I would agree that the original intent of random_device is to provide truly random numbers. However there is an explicit clause (</span><span style="font-size:10.0pt;font-family:LMRoman10-Regular">§</span><span style="color:#1F497D">26.5.6.2
in the C++14 standard) that blesses the use of a random number engine for implementations where non-deterministic random numbers are not supported.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">JB<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Ben Craig [mailto:ben.craig@ni.com]
<br>
<b>Sent:</b> Wednesday, September 13, 2017 8:39 AM<br>
<b>To:</b> Nagurne, James; cfe-dev@lists.llvm.org<br>
<b>Subject:</b> [EXTERNAL] RE: [libc++] Porting libc++ to embedded targets/compilers<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">>- The implementation of std::random_device does not support utilizing a random number engine in the absence of implementation-specific non-deterministic RNGs<o:p></o:p></p>
<p class="MsoNormal">>Two third-party library solutions, arc4 and Sodium, and two /platform-specific solutions, Unix-like /dev/random and Microsoft srand_s are supported.<o:p></o:p></p>
<p class="MsoNormal">>Could a fallback macro be used to implement random_device via another engine found in the random header? I think std::mt19937 is the simplest random engine that supports the full range of values of unsigned int.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The intent of the standard and the expectation of users is that std::random_device provide true random (and not pseudo-random) numbers. In my opinion, it is better to omit std::random_device than it would be to make it provide pseudo-random
numbers. If a user only needs pseudo-random numbers, then they can directly use the pseudo-random facilities.<o:p></o:p></p>
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