commit 28eed06cbf1d1d6183142743192b7eb3aafd605c
author Peter Collingbourne <peter@pcc.me.uk> Wed Dec 09 13:30:52 2020 -0800
committer Copybara-Service <copybara-worker@google.com> Tue Dec 15 00:11:45 2020 -0800
tree e7484744989aa4ab102445dd2d688f739a59a0a5
parent e879d1f83386c9e58937ef4cbbe5719bce43695f

scudo: Shrink secondary header and cache entry size by a word on Linux. NFCI.

Normally compilers will allocate space for struct fields even if the
field is an empty struct. Use the [[no_unique_address]] attribute to
suppress that behavior. This attribute that was introduced in C++20,
but compilers that do not support [[no_unique_address]] will ignore
it since it uses C++11 attribute syntax.

Differential Revision: https://reviews.llvm.org/D92966

GitOrigin-RevId: a7790508522fc277963df974dc953077778e3c11

secondary.h

diff --git a/secondary.h b/secondary.h
index eda8886..ff41bd3 100644
--- a/secondary.h
+++ b/secondary.h
@@ -31,7 +31,7 @@
   uptr BlockEnd;
   uptr MapBase;
   uptr MapSize;
-  MapPlatformData Data;
+  [[no_unique_address]] MapPlatformData Data;
 };
 
 constexpr uptr getHeaderSize() {
@@ -232,7 +232,7 @@
     uptr BlockEnd;
     uptr MapBase;
     uptr MapSize;
-    MapPlatformData Data;
+    [[no_unique_address]] MapPlatformData Data;
     u64 Time;
   };