<div dir="ltr">Currently expensive checks are guarded with command line flags. It&#39;d be nice if there could be one unified command line flag -expensivechecks that subsumes -checkmempool and so on.</div><div class="gmail_extra">
<br><br><div class="gmail_quote">On Wed, Jun 4, 2014 at 6:42 PM, Jannis Froese <span dir="ltr">&lt;<a href="mailto:s9jafroe@stud.uni-saarland.de" target="_blank">s9jafroe@stud.uni-saarland.de</a>&gt;</span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">

  
    
  
  <div text="#000000" bgcolor="#FFFFFF">
    <div>There are reasons to have assertions
      enabled by default in software like Bitcoin Core, where incorrect
      behaviour can be costly. But this comes at a prize: our assertions
      have to satisfy certain performance requirements. It&#39;s no longer
      possible to do expensive, redundant checks in performance critical
      code, which is one of the main advantages of asserts. Imho,
      asserts are not intended for small range checks etc, but are meant
      for checks that a hash hasn&#39;t changed, that a tree structure is
      still a tree, that data is still sorted, or that data structures
      are in sync.<br>
      <br>
      I think most concerns about the current use of asserts would be
      resolved if the currently used asserts would be changed to a nicer
      definition which is independent of NDEBUG, and a second class of
      debugging asserts would be introduced, which is exclusively for
      expensive, redundant checks and is disabled by NDEBUG.<br>
      <br>
      <br>
      <br>
      Am 2014-06-04 12:15, schrieb Gregory Maxwell:<br>
    </div>
    <blockquote type="cite"><div><div class="h5">
      <div dir="ltr">On Wed, Jun 4, 2014 at 2:51 AM, Mike Hearn <span dir="ltr">&lt;<a href="mailto:mike@plan99.net" target="_blank">mike@plan99.net</a>&gt;</span>
        wrote:<br>
        <div class="gmail_extra">
          <div class="gmail_quote">
            <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
              <div dir="ltr">Hi Ron,
                <div><br>
                </div>
                <div>FYI your mail is being spamfoldered due to Yahoo&#39;s
                  DMARC policy and the brokenness of the SF.net mailing
                  list software. I would not expect to get replies
                  reliably whilst this is the case. I think we should
                  move away from SF.net for hosting mailing lists
                  personally, because it&#39;s this list that&#39;s at fault not
                  Yahoo, but until then you may wish to send to the list
                  with a different email address.</div>
                <div><br>
                </div>
                <div>As to your question,</div>
                <div class="gmail_extra">
                  <div class="gmail_quote"><br>
                    <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
                      <div>
                        <div style="color:#000;background-color:#fff;font-family:Courier New,courier,monaco,monospace,sans-serif;font-size:10pt">
                          <div>
                            <div>
                              <div style="color:#000;background-color:#fff;font-family:Courier New,courier,monaco,monospace,sans-serif;font-size:10pt">
                                <div style="color:rgb(0,0,0);font-size:13.3333px;font-family:Courier New,courier,monaco,monospace,sans-serif;background-color:transparent;font-style:normal">
                                  <tt>assert() </tt>should have <span style="text-decoration:underline"><b>no</b></span>
                                  side effects, that is the problem.<br>
                                  <br>
                                  See<br>
                                  <a rel="nofollow" href="http://books.google.com/books?id=L5ZbzVnpkXAC&amp;pg=PA72&amp;lpg=PA72&amp;dq=Gotcha+%2328+Side+Effects&amp;source=bl&amp;ots=Rn15TlPmje&amp;sig=tymHqta0aSANwaM2GaXC-1Di_tk&amp;hl=en&amp;sa=X&amp;ei=uVKNU47fCcvTsAT6goHIBA&amp;ved=0CCAQ6AEwAA#v=onepage&amp;q=Gotcha%20%2328%20Side%20Effects&amp;f=false" target="_blank">http://books.google.com/books?id=L5ZbzVnpkXAC&amp;pg=PA72&amp;lpg=PA72&amp;dq=Gotcha+%2328+Side+Effects&amp;source=bl&amp;ots=Rn15TlPmje&amp;sig=tymHqta0aSANwaM2GaXC-1Di_tk&amp;hl=en&amp;sa=X&amp;ei=uVKNU47fCcvTsAT6goHIBA&amp;ved=0CCAQ6AEwAA#v=onepage&amp;q=Gotcha%20%2328%20Side%20Effects&amp;f=false</a><br>

                                  <br>
                                  a great book, BTW.  Everyone who
                                  thinks they know what they are doing
                                  when they write C++ should read this
                                  book!  They will realize that they
                                  don&#39;t know Jack <img alt="Roll
                                    Eyes" border="0"></div>
                                <div style="color:rgb(0,0,0);font-size:13.3333px;font-family:Courier New,courier,monaco,monospace,sans-serif;background-color:transparent;font-style:normal">
                                  <br>
                                </div>
                                <div style="color:rgb(0,0,0);font-size:13.3333px;font-family:Courier New,courier,monaco,monospace,sans-serif;background-color:transparent;font-style:normal">Why
                                  weren&#39;t these and all the other
                                  examples of amateur, i.e.,
                                  non-professional, software fixed way
                                  back in version 0.3.0 in 2010, before
                                  any more releases were done?  And why
                                  were these and other sub-standard
                                  coding practices continued and
                                  expanded in later releases, right up
                                  until the present? <br>
                                </div>
                              </div>
                            </div>
                          </div>
                        </div>
                      </div>
                    </blockquote>
                    <div><br>
                    </div>
                    <div>Back in 2010 most code was still being written
                      by Satoshi so perhaps you should ask him.
                      Regardless, it&#39;s very common for professional
                      codebases to require assertions be enabled. For
                      example the entire Google C++ codebase uses
                      always-on assertions that have side effects
                      liberally: it&#39;s convenient and safe, when you have
                      the guarantee the code will always run, and the
                      performance benefits of compiling out assertions
                      are usually non-existent.</div>
                    <div><br>
                    </div>
                    <div>So for this reason I think Bitcoin Core
                      currently will fail to build if assertions are
                      disabled, and that seems OK to me.</div>
                  </div>
                </div>
              </div>
            </blockquote>
            <div><br>
            </div>
            <div>As a matter of procedure we do not use assertions with
              side effects— the codebase did at one point, but have
              cleaned them up.  In an abundance of caution we also made
              it refuse to compile without assertions enabled: A
              decision who&#39;s wisdom was clearly demonstrated when not
              long after, some additional side-effect having assert was
              contributed. In the real world errors happen here and
              there, and making robust software involves defense in
              depth.<br>
              <br>
            </div>
            <div>Considering the normal criticality of the software it
              should always be with the assertions. Without them is an
              untested configuration.  It would probably be superior to
              use our own assertion macros (for one, they can give some
              better reporting…) that don&#39;t have the baggage ordinary
              assertions have, but as a the codebase is a production
              thing, making larger changes all at once to satisfy
              aesthetics would be unwise... simply refusing to compile
              in that untested, unsupported configuration is prudent,
              for the time being.<br>
              <br>
            </div>
          </div>
        </div>
      </div>
      <br>
      <fieldset></fieldset>
      <br>
      </div></div><pre>------------------------------------------------------------------------------
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this first edition is now available. Download your free book today!<br>
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