[compiler-rt] [scudo] Add hooks to mark the range of realloc (PR #74353)

[Christopher Ferris via llvm-commits]

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@@ -20,6 +20,20 @@ __attribute__((weak)) const char *__scudo_default_options(void);
 __attribute__((weak)) void __scudo_allocate_hook(void *ptr, size_t size);
 __attribute__((weak)) void __scudo_deallocate_hook(void *ptr);
 
+// `realloc` involves both deallocation and allocation but they are not reported
+// atomically. In one specific case which may keep taking a snapshot right in
+// the middle of `realloc` reporting the deallocation and allocation, it may
+// confuse the user by the missing memory from `realloc`. To alleviate that
+// case, define the two `realloc` hooks to get the knowledge of the bundled hook
+// calls. This hooks are optional and only used when you are pretty likely to
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cferris1000 wrote:

This -> These

and only used when you are pretty likely to -> and should only be used when a hooks user wants to track reallocs more closely.

or something similar.

https://github.com/llvm/llvm-project/pull/74353