Fix clang UBSan trigger in sbo_resource.hpp

lzulberti · lzulberti · commit c9e28ffd8bb9 · 2026-05-21T08:30:35.000+02:00
diff --git a/include/boost/cobalt/detail/sbo_resource.hpp b/include/boost/cobalt/detail/sbo_resource.hpp
@@ -41,12 +41,12 @@ struct sbo_resource
   }
   constexpr void align_as_max_()
   {
-    const auto buffer = static_cast<char*>(buffer_.p) - static_cast<char*>(nullptr);
+    const auto buffer = reinterpret_cast<std::uintptr_t>(buffer_.p);
     const auto diff = buffer % alignof(std::max_align_t );
     if (diff > 0)
     {
       const auto padding = alignof(std::max_align_t) - diff;
-      buffer_.p = static_cast<void*>(static_cast<char*>(nullptr) + buffer + padding);
+      buffer_.p = static_cast<char*>(buffer_.p) + padding;
       if (padding >= buffer_.size) [[unlikely]]
       {
         buffer_.size = 0;

Original file line number	Diff line number	Diff line change
`@@ -41,12 +41,12 @@ struct sbo_resource`
`41`	`41`	`}`
`42`	`42`	`constexpr void align_as_max_()`
`43`	`43`	`{`
`44`		`- const auto buffer = static_cast<char>(buffer_.p) - static_cast<char>(nullptr);`
	`44`	`+ const auto buffer = reinterpret_cast<std::uintptr_t>(buffer_.p);`
`45`	`45`	`const auto diff = buffer % alignof(std::max_align_t );`
`46`	`46`	`if (diff > 0)`
`47`	`47`	`{`
`48`	`48`	`const auto padding = alignof(std::max_align_t) - diff;`
`49`		`- buffer_.p = static_cast<void>(static_cast<char>(nullptr) + buffer + padding);`
	`49`	`+ buffer_.p = static_cast<char*>(buffer_.p) + padding;`
`50`	`50`	`if (padding >= buffer_.size) [[unlikely]]`
`51`	`51`	`{`
`52`	`52`	`buffer_.size = 0;`