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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I recompiled TI’s runtime library with the original block size from trunk and do not have issues.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">So my question is, is a block size of 1 unsupported, and therefor the error is in TI’s changes? Or is there an error in _add_back_capacity()?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Why does __add_back_capacity(1) allocate more blocks if the base is empty, while __add_back_capacity() makes no check?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I’m talking about line 2510 of
<a href="https://github.com/llvm-mirror/libcxx/blob/master/include/deque">https://github.com/llvm-mirror/libcxx/blob/master/include/deque</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">FYI, w/o changes to TI’s code, as long as I resize(1) first, then push_back() will work just fine thereafter!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Somehow just that first push_back screws something up.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I really don’t want to have to run a modified version of TI’s runtime, but may have to.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Marshall Clow [mailto:mclow.lists@gmail.com]
<br>
<b>Sent:</b> Tuesday, April 2, 2019 4:04 PM<br>
<b>To:</b> Jason MacDonald <jason.macdonald@ditchwitch.com>; libcxx-dev@lists.llvm.org<br>
<b>Subject:</b> Re: [libcxx-dev] deque, block_size, __add_back_capacity<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p align="center" style="text-align:center;line-height:18.0pt;background:#CCCC00">
<b><span style="font-family:"Cambria",serif">Think Before You Click:</span></b><span style="font-family:"Cambria",serif"> This email originated
<b>outside</b> our organization. <o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Tue, Apr 2, 2019 at 8:55 AM Jason MacDonald via libcxx-dev <<a href="mailto:libcxx-dev@lists.llvm.org">libcxx-dev@lists.llvm.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hello all,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">First, apologizes if this is the wrong mailing list for this discussion.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">This is not a terrible place.<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> I am using the TI 18.1.5 compiler to compile for the TM4C1294NCPDT chip. A longer/better explanation of my problems might be obtained from the TI forums of my issue, which didn’t
gain traction: <a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__e2e.ti.com_support_tools_ccs_f_81_t_787948&d=DwMFaQ&c=G4BpsyPyB19LB50bn2swXw&r=2z0vjupNNnhHhgc2c7HiUGlYDV8dSFvIGZRHV7-Giy8&m=cSTTEZftPo7skIefkh_qd4wKIAeJV3pt3zB7h5L7znY&s=rVckol1NRCLS5HnIfykH8Af8a5shQ8nmuu3jrU9rZZo&e=" target="_blank">
https://e2e.ti.com/support/tools/ccs/f/81/t/787948</a><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">So I am trying to go upstream for more discussion.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Summary of my problem: Using deque::push_back on structures over 64 bytes will cause a crash.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Example code:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New";color:#555555">#include <deque>
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New";color:#555555">struct</span><span style="font-size:10.5pt;font-family:Consolas;color:#555555">
</span><span style="font-size:10.0pt;font-family:"Courier New";color:#555555">s {
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New";color:#555555"> char</span><span style="font-size:10.5pt;font-family:Consolas;color:#555555">
</span><span style="font-size:10.0pt;font-family:"Courier New";color:#555555">d[65];
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New";color:#555555">};
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New";color:#555555">int</span><span style="font-size:10.5pt;font-family:Consolas;color:#555555">
</span><span style="font-size:10.0pt;font-family:"Courier New";color:#555555">main()
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New";color:#555555">{
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New";color:#555555"> int</span><span style="font-size:10.5pt;font-family:Consolas;color:#555555">
</span><span style="font-size:10.0pt;font-family:"Courier New";color:#555555">size = sizeof(s);
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New";color:#555555">
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New";color:#555555"> std::deque<s> test;
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New";color:#555555"> test.push_back(s());
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New";color:#555555"> test.push_back(s()); // will crash here
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New";color:#555555"> while</span><span style="font-size:10.5pt;font-family:Consolas;color:#555555">
</span><span style="font-size:10.0pt;font-family:"Courier New";color:#555555">(1){}
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New";color:#555555">}</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I tried this on my desktop, and it did not crash.<o:p></o:p></p>
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<p class="MsoNormal">I also turned on address sanitizer to see if there might be an out-of-bounds read or write, but it didn't report any.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I tried your second program (again, on my desktop), and added some printf statements, and I got:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">back_spare cap<o:p></o:p></p>
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<p class="MsoNormal">61 62<o:p></o:p></p>
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<p class="MsoNormal">61 62<o:p></o:p></p>
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<p class="MsoNormal">62 62<o:p></o:p></p>
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<p class="MsoNormal">62 62<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">TI’s implementation of the struct __deque_block_size allows a minimum size of 1. Not sure if this should cause a problem or not.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">TI:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New"">template <class _ValueType, class _DiffType></span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New"">struct __deque_block_size {</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New""> enum __attribute__((__packed__)) { _MAX_BYTES = 32 * sizeof(void*) };</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New""> static const _DiffType value = sizeof(_ValueType) < _MAX_BYTES ? (_MAX_BYTES / sizeof(_ValueType)) : 1;</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:10.0pt;font-family:"Courier New"">};</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">So, is this a problem in LLVM’s __add_back_capacity() or TI’s block_size?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I'm suspecting TI's block_size. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">here's the one from trunk:<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">template <class _ValueType, class _DiffType><o:p></o:p></p>
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<p class="MsoNormal">struct __deque_block_size {<o:p></o:p></p>
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<p class="MsoNormal"> static const _DiffType value = sizeof(_ValueType) < 256 ? 4096 / sizeof(_ValueType) : 16;<o:p></o:p></p>
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<p class="MsoNormal">};<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Note that it never is smaller than 16.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">-- Marshall<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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