release/22.x: [MC] Try to fix ubsan bot#177907
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c-rhodes merged 1 commit intollvm:release/22.xfrom Feb 3, 2026
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@llvm/pr-subscribers-llvm-mc Author: None (llvmbot) ChangesBackport d064f39 Requested by: @nikic 1 Files Affected:
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index 5fd30eccb45c5..0c64d89d7b491 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -111,7 +111,8 @@ void MCObjectStreamer::appendContents(ArrayRef<char> Contents) {
assert(FragSpace >= Contents.size());
// As this is performance-sensitive code, explicitly use std::memcpy.
// Optimization of std::copy to memmove is unreliable.
- std::memcpy(getCurFragEnd(), Contents.begin(), Contents.size());
+ if (!Contents.empty())
+ std::memcpy(getCurFragEnd(), Contents.begin(), Contents.size());
CurFrag->FixedSize += Contents.size();
FragSpace -= Contents.size();
}
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(This did fix the ubsan buildbot.) |
c-rhodes
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Feb 3, 2026
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seems like a simple fix that worked so im just going to go ahead and approve so we can land this
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Check that the size is non-zero to make sure we don't call memcpy with null pointers. This is well-defined now, but ubsan may still warn about it. (cherry picked from commit d064f39)
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Backport d064f39
Requested by: @nikic