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<p class="MsoNormal"><span lang="EN-US">Hi erlangers,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I'm wondering whether itís necessary to check that port is not NULL in the start callback of the driver:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">ErlDrvData (*start)(ErlDrvPort port, char *command);<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Iím asking because there are some samples that do such a verification, i.e.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><a href="https://github.com/dlfen/erlang-db-driver/blob/master/c_src/base/AsyncDrv.cpp#L29">https://github.com/dlfen/erlang-db-driver/blob/master/c_src/base/AsyncDrv.cpp#L29</a><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><a href="https://github.com/norton/lets/blob/master/c_src/lets_drv.cc#L251">https://github.com/norton/lets/blob/master/c_src/lets_drv.cc#L251</a><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">and a lot of port drivers that do not.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">As I understand (according to the otp sources) port parameter is only a number of the port in the erts_port array (<a href="https://github.com/erlang/otp/blob/maint/erts/emulator/beam/io.c#L60">https://github.com/erlang/otp/blob/maint/erts/emulator/beam/io.c#L60</a>)
 and 0 (zero) is a valid value for it.<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US">So I have two questions:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><![if !supportLists]><span lang="EN-US"><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman"">      
</span></span></span><![endif]><span lang="EN-US">Is it necessary to check that the port parameter in the start callback of the driver is not NULL (not 0) and why?<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><![if !supportLists]><span lang="EN-US"><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman"">      
</span></span></span><![endif]><span lang="EN-US">If 0 (zero) is a legal value for the port parameter in the start callback of the driver, why there are drivers which require that parameter to be not NULL (or this is a kind of a bug)?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="color:black;mso-fareast-language:RU">Best Regards,<o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span lang="EN-US" style="color:black;mso-fareast-language:RU">Sergey<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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