<div dir="ltr"><div><div><div>The problem we ran into was when we had a struct like this:<br><br></div>struct table {<br></div> uint16_t size;<br></div> struct element elements[0];<br><div><div>};<br><div><div><div class="gmail_extra"><br></div><div class="gmail_extra">and then we would try and index the array:<br><br></div><div class="gmail_extra">for (i = 0; i < table->size; i++) {<br></div><div class="gmail_extra"> element = &table->elements[i];<br></div><div class="gmail_extra">}<br><br></div><div class="gmail_extra">element ended up off in the weeds. The only thing that seems to make some versions of gcc happy was pointer arithmetic. E.g.,<br></div><div class="gmail_extra"><br></div><div class="gmail_extra">element = (struct element *)((char *)&table->elements[0] + (sizeof(struct element) * i));<br><br></div><div class="gmail_extra">Alex<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Aug 18, 2016 at 11:21 AM, StDenis, Tom <span dir="ltr"><<a href="mailto:Tom.StDenis@amd.com" target="_blank">Tom.StDenis@amd.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> <div dir="ltr"> <div style="font-size:12pt;color:#000000;background-color:#ffffff;font-family:Calibri,Arial,Helvetica,sans-serif"> <p>Any modern GCC should support [0] at the tail of a struct. This came up because when I was reading the code I saw they allocated 7 slots (plus the size of the struct) but then fill 8 slots. It's just weird <img alt="😊" style="vertical-align:bottom" src="cid:b9d342ca-4063-4b61-a23c-e54ecb4cfb09"></p> <p><br> </p> <p>Using [0] in the struct and allocating for 8 entries makes more sense and is clearer to read.</p> <p><br> </p> <p>Tom</p> <br> <br> <div style="color:rgb(0,0,0)"> <hr style="display:inline-block;width:98%"> <div dir="ltr"><font style="font-size:11pt" color="#000000" face="Calibri, sans-serif"><b>From:</b> Christian König <<a href="mailto:deathsimple@vodafone.de" target="_blank">deathsimple@vodafone.de</a>><br> <b>Sent:</b> Thursday, August 18, 2016 11:17<br> <b>To:</b> StDenis, Tom; amd-gfx list<br> <b>Subject:</b> Re: tidy'ing up cz_hwmgr.c</font> <div> </div> </div><div><div class="h5"> <div> <div> <blockquote type="cite"> <div>Has a [1] array at the tail which is then kzalloc'ed with N-1 entries. Shouldn't that just be a [0] with N entries allocated for clarity?</div> </blockquote> Actually the starting address of a dynamic array should be manually calculated instead of using [1] or [0].<br> <br> We had tons of problems with that because some gcc versions get this wrong and the atombios code used this as well.<br> <br> Alex how did we resolved such issues?<br> <br> Regards,<br> Christian.<br> <br> Am 18.08.2016 um 16:26 schrieb StDenis, Tom:<br> </div> <blockquote type="cite"> <div style="font-size:12pt;color:#000000;background-color:#ffffff;font-family:Calibri,Arial,Helvetica,sans-serif"> <p>Tidying up cz_hwmgr.c I noted a couple of things but first is </p> <p><br> </p> <div><span style="font-family:"Courier New",monospace">static bool cz_dpm_check_smu_features(<wbr>struct pp_hwmgr *hwmgr,</span></div> <div><span style="white-space:pre-wrap;font-family:"Courier New",monospace"></span><span style="font-family:"Courier New",monospace">unsigned long check_feature);</span></div> <div><br> </div> <div>Which will return "true" if the smu call fails <b>or</b> the feature is set. </div> <div><br> </div> <div>The structure </div> <div><br> </div> <div> <div><span style="font-family:"Courier New",monospace">struct phm_clock_voltage_dependency_<wbr>table;</span></div> </div> <div><br> </div> <div>Has a [1] array at the tail which is then kzalloc'ed with N-1 entries. Shouldn't that just be a [0] with N entries allocated for clarity?</div> <div><br> </div> <div>Tom</div> <div><br> </div> </div> <br> <fieldset></fieldset> <br> <pre>______________________________<wbr>_________________ amd-gfx mailing list <a href="mailto:amd-gfx@lists.freedesktop.org" target="_blank">amd-gfx@lists.freedesktop.org</a> <a href="https://lists.freedesktop.org/mailman/listinfo/amd-gfx" target="_blank">https://lists.freedesktop.org/<wbr>mailman/listinfo/amd-gfx</a> </pre> </blockquote> <p><br> </p> </div> </div></div></div> </div> </div> <br>______________________________<wbr>_________________<br> amd-gfx mailing list<br> <a href="mailto:amd-gfx@lists.freedesktop.org">amd-gfx@lists.freedesktop.org</a><br> <a href="https://lists.freedesktop.org/mailman/listinfo/amd-gfx" rel="noreferrer" target="_blank">https://lists.freedesktop.org/<wbr>mailman/listinfo/amd-gfx</a><br> <br></blockquote></div><br></div></div></div></div></div></div>