<div dir="ltr">Looks like everything is set, but let me try to explain a little bit.<div><br></div><div>The /O1 and /O2 options of MSVC and clang-cl actually expand to several other options. You can see this in the docs:</div><div><a href="https://docs.microsoft.com/en-us/cpp/build/reference/o1-o2-minimize-size-maximize-speed?view=msvc-160">https://docs.microsoft.com/en-us/cpp/build/reference/o1-o2-minimize-size-maximize-speed?view=msvc-160</a><br></div><div>/O2 (Maximize Speed) /Og /Oi /Ot /Oy /Ob2 /GF /Gy<br></div><div><br></div><div>In particular, /Gy means -ffunction-sections. If you were building your code with optimizations enabled, (`clang-cl /O2 /c foo.cpp`), that would explain why you see one section per function.</div><div><br></div><div>If you want to disable function sections more directly, consider passing the /Gy- flag after the /O2 flag.</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Jan 20, 2021 at 7:17 AM Gaier, Bjoern via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org">cfe-dev@lists.llvm.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<p class="MsoNormal"><span lang="EN-GB">Allright :’D<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-GB"><u></u> <u></u></span></p>
<p class="MsoNormal"><span lang="EN-GB">That worked! Now my 100x functions are in one section! Thank you so much guys!<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-GB"><u></u> <u></u></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Keane, Erich <<a href="mailto:erich.keane@intel.com" target="_blank">erich.keane@intel.com</a>>
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<b>Sent:</b> 20 January 2021 16:13<br>
<b>To:</b> Gaier, Bjoern <<a href="mailto:Bjoern.Gaier@horiba.com" target="_blank">Bjoern.Gaier@horiba.com</a>>; <a href="mailto:paul.robinson@sony.com" target="_blank">paul.robinson@sony.com</a>; clang developer list <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a>><br>
<b>Subject:</b> RE: Clang function-sections flag<u></u><u></u></span></p>
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<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><span lang="EN-US">/clang: sends to the ‘driver’. -Xclang sends to the ‘compiler instance’ (the -cc1 compiler), which the driver calls. They are actually the same executable which makes it a touch more confusing.<u></u><u></u></span></p>
<p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Gaier, Bjoern <<a href="mailto:Bjoern.Gaier@horiba.com" target="_blank">Bjoern.Gaier@horiba.com</a>>
<br>
<b>Sent:</b> Wednesday, January 20, 2021 7:11 AM<br>
<b>To:</b> Keane, Erich <<a href="mailto:erich.keane@intel.com" target="_blank">erich.keane@intel.com</a>>;
<a href="mailto:paul.robinson@sony.com" target="_blank">paul.robinson@sony.com</a>; clang developer list <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a>><br>
<b>Subject:</b> RE: Clang function-sections flag<u></u><u></u></span></p>
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<p class="MsoNormal"><span lang="EN-US"><u></u> <u></u></span></p>
<p class="MsoNormal"><span lang="EN-GB">Using /clang:-fno-function-sections and /clang:-ffunction-sections were both accepted by Clang-cl while /clang:-planschbecken was rejected.</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">Seems like that worked O_O Thank you!<br>
I gonna check if this will make a difference now.</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">In the meantime… why isn’t /clang: and -Xclang the same?!</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><u></u><u></u></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Keane, Erich <<a href="mailto:erich.keane@intel.com" target="_blank">erich.keane@intel.com</a>>
<br>
<b>Sent:</b> 20 January 2021 16:07<br>
<b>To:</b> Gaier, Bjoern <<a href="mailto:Bjoern.Gaier@horiba.com" target="_blank">Bjoern.Gaier@horiba.com</a>>;
<a href="mailto:paul.robinson@sony.com" target="_blank">paul.robinson@sony.com</a>; clang developer list <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a>><br>
<b>Subject:</b> RE: Clang function-sections flag</span><u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-US">Looks like CloudABI is the only triple that uses it by default. Presumably you aren’t on that, but I could also be missing something.</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-US"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-US">For me, it looks like BOTH -ffunction-sections and -fno-function-sections are unknown arguments in clang-cl, however if you use the /clang: syntax, both work. Can you try that?</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-US"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-US">/clang:-fno-function-sections</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-US"> </span><u></u><u></u></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> cfe-dev <<a href="mailto:cfe-dev-bounces@lists.llvm.org" target="_blank">cfe-dev-bounces@lists.llvm.org</a>>
<b>On Behalf Of </b>Gaier, Bjoern via cfe-dev<br>
<b>Sent:</b> Wednesday, January 20, 2021 7:00 AM<br>
<b>To:</b> <a href="mailto:paul.robinson@sony.com" target="_blank">paul.robinson@sony.com</a>; <a href="mailto:cfe-dev@lists.llvm.org" target="_blank">
cfe-dev@lists.llvm.org</a><br>
<b>Subject:</b> Re: [cfe-dev] Clang function-sections flag</span><u></u><u></u></p>
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<p class="MsoNormal"><span lang="EN-US"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">Hey Paul,</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">I tried that already and got:</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">“error: unknown argument: '-fno-function-sections'”</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">I use Clang-Cl under Windows, creating an ELF file for x86_64-pc-windows-elf – however the flag is not supported (not with -Xclang but also not without)</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">However “-ffunction-sections” is accepted (with -Xclang)</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">Kind greetings</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">Björn</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><u></u><u></u></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> <a href="mailto:paul.robinson@sony.com" target="_blank">
paul.robinson@sony.com</a> <<a href="mailto:paul.robinson@sony.com" target="_blank">paul.robinson@sony.com</a>>
<br>
<b>Sent:</b> 20 January 2021 15:56<br>
<b>To:</b> Gaier, Bjoern <<a href="mailto:Bjoern.Gaier@horiba.com" target="_blank">Bjoern.Gaier@horiba.com</a>>;
<a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a><br>
<b>Subject:</b> RE: Clang function-sections flag</span><u></u><u></u></p>
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<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-US">Try adding -fno-function-sections to make sure it’s turned off (sounds like it is on by default for your target).</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-US">--paulr</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-US"> </span><u></u><u></u></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> cfe-dev <<a href="mailto:cfe-dev-bounces@lists.llvm.org" target="_blank">cfe-dev-bounces@lists.llvm.org</a>>
<b>On Behalf Of </b>Gaier, Bjoern via cfe-dev<br>
<b>Sent:</b> Wednesday, January 20, 2021 5:01 AM<br>
<b>To:</b> Clang Dev <<a href="mailto:cfe-dev@lists.llvm.org" target="_blank">cfe-dev@lists.llvm.org</a>><br>
<b>Subject:</b> [cfe-dev] Clang function-sections flag</span><u></u><u></u></p>
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<p class="MsoNormal"><span lang="EN-US"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">Hey Clang-people,</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">I have a nooby question about the -ffunction-sections flag of Clang.
</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">As far as I used to understand, setting this flag means, that every function gets their own section. Makes sense so far.</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">Recently I started to look into the ELF format a bit so that subject came up. I created a macro to quickly generate me some functions:</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">#define wuff(a, b) \</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">a##b</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="MsoNormal">#define crap(num) \<u></u><u></u></p>
<p class="MsoNormal">int wuff(schwimmflugel, num) () \<u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">{ \</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> return num; \</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">}</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">Creating the object file and looking into it, I found a section header for every of my functions no matter if I set the -ffunction-sections flag or not.</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">Also setting my function to static didn't changed a thing.... well besides from having those functions striped from my object file xD</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">So... what does that flag effect?</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB"> </span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">Kind greetings</span><u></u><u></u></p>
<p class="MsoNormal"><span lang="EN-GB">Björn</span><u></u><u></u></p>
<p class="MsoNormal">Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Takashi Nagano, Junichi Tajika, Ergin Cansiz.
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<p class="MsoNormal">Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Takashi Nagano, Junichi Tajika, Ergin Cansiz.
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<p class="MsoNormal">Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Takashi Nagano, Junichi Tajika, Ergin Cansiz.
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Als GmbH eingetragen im Handelsregister Bad Homburg v.d.H. HRB 9816, USt.ID-Nr. DE 114 165 789 Geschäftsführer: Dr. Hiroshi Nakamura, Dr. Robert Plank, Markus Bode, Takashi Nagano, Junichi Tajika, Ergin Cansiz.
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