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<p style="margin-top:0;margin-bottom:0">Hello, </p>
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<p style="margin-top:0;margin-bottom:0">In my organization, we've been using ASAN and most of UBSAN checks in the default developers mode with a big success. I'd like to enable a few remaining UBSAN checks too but noticed that they cause significant (up to
2x in some cases) binary size overhead (mostly .rodata and .data). These checks are: null, function, vptr, object-size. </p>
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<p style="margin-top:0;margin-bottom:0">Inspecting .rodata, it looks like there are a lot of strings with file and type names. <span style="font-size: 12pt;">I tried to use `<span>-fsanitize-undefined-strip-path-components=-1` from [1]. It appeared to have
no effect when `-fsanitize=function` and `-fsanitize=address` are used at the same time (filed bug [2]). Disabling `-fsanitize=function` and using <span style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;">`</span><span style="font-family: Calibri, Helvetica, sans-serif, Helvetica, EmojiFont, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;">-fsanitize-undefined-strip-path-components=-1`
reduces the size overhead to 1.4x. </span></span></span>This is quite already significant.</p>
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<p style="margin-top:0;margin-bottom:0">I've considered -fsanitize=trap, it causes very little size overhead but it in some cases is hard to work with. </p>
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<p style="margin-top:0;margin-bottom:0">I noticed that [3] added minimal runtime for UBSAN. It works similar to `<span>-fsanitize-trap`, but prints a bit more informative message, which would suffice. Out of the box, I didn't notice a measurable binary size
reduction as mentioned on that change, but if used with `<span>-fdata-sections -ffunction-sections -Wl,--gc-sections -Wl,--print-gc-sections`, the size bloat of .rodata and .data is almost eliminated. Note, in this case, those flags don't help without `-<span>fsanitize-minimal-runtime`.</span></span></span></p>
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<p style="margin-top:0;margin-bottom:0"><span><span><span>Unfortunately, there is a restriction in the driver preventing this minimal UBSAN runtime to be used when ASAN is also enabled. I don't completely understand the reasons for having this restriction.
When I removed that restriction, both ASAN and UBSAN still seem functioning in my tests. </span></span></span></p>
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</span></span></span></p>
<p style="margin-top:0;margin-bottom:0"><span><span><span>I'd like to allow using minimal UBSAN runtime with ASAN. Are there reasons against it? I'd volunteer to do the work here.</span></span></span></p>
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</span></span></span></p>
<p style="margin-top:0;margin-bottom:0"><span><span><span>Also, v<span>ptr UBSAN check is disallowed when minimal UBSAN runtime is used. Would someone clarify why?</span></span></span></span></p>
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</span></span></span></span></p>
<p style="margin-top:0;margin-bottom:0">-- Igor</p>
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<li><a href="https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html#additional-configuration" class="OWAAutoLink" id="LPlnk224361" previewremoved="true">https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html#additional-configuration</a></li><li><span style="font-size: 12pt;"></span><a href="https://bugs.llvm.org/show_bug.cgi?id=39347" class="OWAAutoLink" id="LPlnk663307" previewremoved="true">https://bugs.llvm.org/show_bug.cgi?id=39347</a></li><li><a href="https://reviews.llvm.org/D36810" class="OWAAutoLink" id="LPlnk471537" previewremoved="true">https://reviews.llvm.org/D36810</a>
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<a id="LPUrlAnchor_15399093196720.8406941018844281" href="https://reviews.llvm.org/D36810" target="_blank" style="text-decoration: none;">D36810 Minimal runtime for UBSan. - LLVM</a></div>
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reviews.llvm.org</div>
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Not worried about that. If it allocates or prints too much, we can add in a custom allocator or printing strategy. If it requires too much metadata to be inserted into user programs, we can devise a new, smaller encoding for the metadata.</div>
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<p style="margin-top:0;margin-bottom:0"><a href="https://reviews.llvm.org/D36810" class="OWAAutoLink" id="LPlnk510871" previewremoved="true">https://reviews.llvm.org/D36810</a></p>
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<div id="LPRemovePreviewContainer_15399077390170.15590685974231056"><a id="LPlnk536017" class="ms-Icon--x ms-icon-font-size-14 OWAAutoLink" style="font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif; font-weight: normal; position: relative; cursor: pointer; padding: 8px; float: right; color: rgb(102, 102, 102); background-color: rgb(238, 247, 255); user-select: none; margin-left: 10px;" previewremoved="true"></a></div>
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<a id="LPUrlAnchor_15399077390170.8827673418982735" href="https://reviews.llvm.org/D36810" target="_blank" style="text-decoration: none;">D36810 Minimal runtime for UBSan. - LLVM</a></div>
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reviews.llvm.org</div>
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Not worried about that. If it allocates or prints too much, we can add in a custom allocator or printing strategy. If it requires too much metadata to be inserted into user programs, we can devise a new, smaller encoding for the metadata.</div>
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