[compiler-rt] sanitizer_allocator.cpp: Ensure at least sizeof(void*) alignment (PR #84440)

[Alexander Richardson via llvm-commits]

https://github.com/arichardson created https://github.com/llvm/llvm-project/pull/84440

Some platforms (e.g. 64-bit CHERI) have stronger alignment requirements
on values returned from allocators. For all other platforms this does
not result in any functional change.


>From 0bf259f52f5dc30c2c89ea3c85b23cc00cff0250 Mon Sep 17 00:00:00 2001
From: Alex Richardson <alexrichardson at google.com>
Date: Thu, 7 Mar 2024 23:36:16 -0800
Subject: [PATCH] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20initia?=
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Created using spr 1.3.6-beta.1
---
 compiler-rt/lib/sanitizer_common/sanitizer_allocator.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_allocator.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_allocator.cpp
index 0513ae36fbc721..d7f8acd819ade2 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_allocator.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_allocator.cpp
@@ -59,7 +59,7 @@ static void *RawInternalAlloc(uptr size, InternalAllocatorCache *cache,
 
 static void *RawInternalRealloc(void *ptr, uptr size,
                                 InternalAllocatorCache *cache) {
-  uptr alignment = 8;
+  constexpr usize alignment = Max<usize>(8, sizeof(void *));
   if (cache == 0) {
     SpinMutexLock l(&internal_allocator_cache_mu);
     return internal_allocator()->Reallocate(&internal_allocator_cache, ptr,
@@ -137,7 +137,8 @@ void InternalAllocatorUnlock() SANITIZER_NO_THREAD_SAFETY_ANALYSIS {
 }
 
 // LowLevelAllocator
-constexpr uptr kLowLevelAllocatorDefaultAlignment = 8;
+constexpr usize kLowLevelAllocatorDefaultAlignment =
+    Max<usize>(8, sizeof(void *));
 constexpr uptr kMinNumPagesRounded = 16;
 constexpr uptr kMinRoundedSize = 65536;
 static uptr low_level_alloc_min_alignment = kLowLevelAllocatorDefaultAlignment;