[scudo] Introduce Chunk::getHeaderSize

Summary:
Instead of using `AlignedChunkHeaderSize`, introduce a `constexpr` function
`getHeaderSize` in the `Chunk` namespace. Switch `RoundUpTo` to a `constexpr`
as well (so we can use it in `constexpr` declarations). Mark a few variables
in the areas touched as `const`.

Overall this has no functional change, and is mostly to make things a bit more
consistent.

Reviewers: alekseyshl

Reviewed By: alekseyshl

Subscribers: delcypher, #sanitizers, llvm-commits

Differential Revision: https://reviews.llvm.org/D43772

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@326206 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 11 insertions, 8 deletions

diff --git a/lib/scudo/scudo_allocator.h b/lib/scudo/scudo_allocator.h
index a561247de..c29edea46 100644
--- a/lib/scudo/scudo_allocator.h
+++ b/lib/scudo/scudo_allocator.h
@@ -59,9 +59,17 @@ const uptr MaxAlignmentLog = 24;  // 16 MB
 const uptr MinAlignment = 1 << MinAlignmentLog;
 const uptr MaxAlignment = 1 << MaxAlignmentLog;
 
-const uptr ChunkHeaderSize = sizeof(PackedHeader);
-const uptr AlignedChunkHeaderSize =
-    (ChunkHeaderSize + MinAlignment - 1) & ~(MinAlignment - 1);
+// constexpr version of __sanitizer::RoundUp without the extraneous CHECK.
+// This way we can use it in constexpr variables and functions declarations.
+constexpr uptr RoundUpTo(uptr Size, uptr Boundary) {
+  return (Size + Boundary - 1) & ~(Boundary - 1);
+}
+
+namespace Chunk {
+  constexpr uptr getHeaderSize() {
+    return RoundUpTo(sizeof(PackedHeader), MinAlignment);
+  }
+}
 
 #if SANITIZER_CAN_USE_ALLOCATOR64
 const uptr AllocatorSpace = ~0ULL;
@@ -97,11 +105,6 @@ struct AP32 {
 typedef SizeClassAllocator32<AP32> PrimaryAllocator;
 #endif  // SANITIZER_CAN_USE_ALLOCATOR64
 
-// __sanitizer::RoundUp has a CHECK that is extraneous for us. Use our own.
-INLINE uptr RoundUpTo(uptr Size, uptr Boundary) {
-  return (Size + Boundary - 1) & ~(Boundary - 1);
-}
-
 #include "scudo_allocator_secondary.h"
 #include "scudo_allocator_combined.h"