<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">2017-05-25 17:49 GMT+02:00 Eliot Miranda <span dir="ltr"><<a href="mailto:eliot.miranda@gmail.com" target="_blank">eliot.miranda@gmail.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi Nicolas,<div class="gmail_extra"><br><div class="gmail_quote"><span class="">On Wed, May 24, 2017 at 11:28 PM, Nicolas Cellier <span dir="ltr"><<a href="mailto:nicolas.cellier.aka.nice@gmail.com" target="_blank">nicolas.cellier.aka.nice@<wbr>gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><div><div><div><div><div><div><div>Great, you reproduced exact same behavior.<br></div>The problem I have is effectively where to put the breakpoint.<br></div><div>I think we can believe the output of (gdb) call printCallStack()<br></div></div></div></div></div></div></div></div></blockquote><div><br></div></span><div>here's one issue; the computation to see if the frame pointer is in use fails. I'm executing this at the compilation break point for <span style="color:rgb(0,0,0);font-size:12.800000190734863px">FilePath class>pathName:isEncoded:</span></div><div><br></div><div>(gdb) print /x CStackPointer</div><div>$7 = 0xef91d0</div><div>(gdb) print /x CFramePointer</div><div>$8 = 0x0</div><div>(gdb) print cFramePointerInUse</div><div>$9 = 0</div><div>(gdb) info registers</div><div>rax 0x68588f 6838415</div><div>rbx 0xffffffff 4294967295</div><div>rcx 0x68588f 6838415</div><div>rdx 0xabababab003a643a -6076574521274768326</div><div>rsi 0xfde9 65001</div><div>rdi 0x0 0</div><div>rbp 0xef5db0 0xef5db0</div><div>rsp 0xef5c50 0xef5c50</div><div>r8 0x0 0</div><div>r9 0xfffffffffbefbc48 -68174776</div><div>r10 0xe36e626d44726839 -2058599758222432199</div><div>r11 0x8101010101010100 -9151031864016699136</div><div>r12 0xffffffff 4294967295</div><div>r13 0x20 32</div><div>r14 0x7ffc202018f0 140720847460592</div><div>r15 0xf2faf0 15923952</div><div>rip 0x4015d9 0x4015d9 <warning+9></div><div>eflags 0x206 [ PF IF ]</div><div>cs 0x33 51</div><div>ss 0x2b 43</div><div>ds 0x2b 43</div><div>es 0x2b 43</div><div>fs 0x53 83</div><div>gs 0x2b 43</div><div>(gdb)</div><span class=""><div> </div></span></div></div></div></blockquote><div><br></div><div>So ceCaptureStackPointers() must get the value of SP and eventually FP in the caller.<br></div><div>For getting caller SP, it must unstack the push RBX, and the return address.<br><br></div><div>But on Win64 ABI it's not enough, because stack space is reserved for the 4 register arguments even if there is less than 4...<br></div><div>So we must add 32 bytes more to callee SP in order to retrieve caller SP...<br></div><div><br></div><div> <br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><span class=""><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><div><div><div><div><div><div></div><div><br></div>I've tried other means:<br></div>- analyze direct usage of registers RCX & co from VMMaker<br> if ever it could conflicts with WIN64 logical register assignment<br></div><div> But I did not find anything<br></div>- compile with MSVC 2017<br></div><div> if ever the compiler could spit different warnings and give a clue<br></div> alas it fails very early in readImageFromFileHeapSizeStart<wbr>ingAt (during checkAssumedCompactClasses)<br></div> the failure is incomprehensible, because the debugger shows identical contents if I print:<br><br> *((sqInt *)(classTableFirstPage+8+(51<<<wbr>3))) 140697255509608 __int64<br> *((sqInt *)(specialObjectsOop+8+(7<<3))<wbr>) 140697255509608 __int64<br><br></div>nonetheless, the debugger enters into the if and execute<br> invalidCompactClassError("Arra<wbr>y");<br><br></div>I'll have to debug it at assembler level, but it's driving me away from the original problem...<br></div></blockquote><div><br></div></span><div>Hmmm. I doubt this is a problem because the assert and debug VMs would print a warning if this were wrong and they seem to be doing fine (I'm using the clang build).</div><div><div class="h5"><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div dir="ltr"></div><div class="m_-6395514045624824347gmail-HOEnZb"><div class="m_-6395514045624824347gmail-h5"><div class="gmail_extra"><br></div></div></div></blockquote></div></div></div></div></div></blockquote><div><br></div><div>This is a MSVC code generation bug.<br> <br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><div><div class="h5"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex"><div class="m_-6395514045624824347gmail-HOEnZb"><div class="m_-6395514045624824347gmail-h5"><div class="gmail_extra"></div>
</div></div></blockquote></div></div></div><span class="HOEnZb"><font color="#888888"><br><br clear="all"><div><br></div>-- <br><div class="m_-6395514045624824347gmail_signature"><div dir="ltr"><div><span style="font-size:small;border-collapse:separate"><div>_,,,^..^,,,_<br></div><div>best, Eliot</div></span></div></div></div>
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