[clangd] Fix undefined behavior due to misaligned type cast

The current code was casting pointer to a misaligned type which is undefined behavior.
Found by compiling with Undefined Behavior Sanitizer and running tests (check-clang-tools).

llvm-svn: 327902

1 files changed, 3 insertions, 1 deletions

diff --git a/clang-tools-extra/clangd/index/Index.h b/clang-tools-extra/clangd/index/Index.h
index 7da3a50ea47..1b752b672fc 100644
--- a/clang-tools-extra/clangd/index/Index.h
+++ b/clang-tools-extra/clangd/index/Index.h
@@ -61,7 +61,9 @@ private:
   friend llvm::hash_code hash_value(const SymbolID &ID) {
     // We already have a good hash, just return the first bytes.
     static_assert(sizeof(size_t) <= HashByteLength, "size_t longer than SHA1!");
-    return *reinterpret_cast<const size_t *>(ID.HashValue.data());
+    size_t Result;
+    memcpy(&Result, ID.HashValue.data(), sizeof(size_t));
+    return llvm::hash_code(Result);
   }
   friend llvm::raw_ostream &operator<<(llvm::raw_ostream &OS,
                                        const SymbolID &ID);