RFR: 8369393: NMT: poison the canaries of malloc header under ASAN build [v7]

[Johan Sjölen]

On Tue, 14 Oct 2025 16:08:54 GMT, Afshin Zafari <azafari at openjdk.org> wrote:

>> src/hotspot/share/sanitizers/address.hpp line 29:
>> 
>>> 27: 
>>> 28: #ifdef ADDRESS_SANITIZER
>>> 29: #define __SANITIZE_ADDRESS__
>> 
>> Why not just check for `ADDRESS_SANITIZER` in the test, and skip this definition?
>
> In `.../clang/15.0.0/include/sanitizer/asan_interface.h`, the ASAN_(UN)POISON_MEMORY_REGION  macros would be empty as  
> ```C++
> // Macros provided for convenience.
> #if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
> /// Marks a memory region as unaddressable.
> ///
> /// \note Macro provided for convenience; defined as a no-op if ASan is not
> /// enabled.
> ///
> /// \param addr Start of memory region.
> /// \param size Size of memory region.
> #define ASAN_POISON_MEMORY_REGION(addr, size) \
>   __asan_poison_memory_region((addr), (size))
> 
> /// Marks a memory region as addressable.
> ///
> /// \note Macro provided for convenience; defined as a no-op if ASan is not
> /// enabled.
> ///
> /// \param addr Start of memory region.
> /// \param size Size of memory region.
> #define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
>   __asan_unpoison_memory_region((addr), (size))
> #else
> #define ASAN_POISON_MEMORY_REGION(addr, size) \
>   ((void)(addr), (void)(size))
> #define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
>   ((void)(addr), (void)(size))
> #endif
> 
> 
> I couldn't find yet why is that. So a fast/certain solution was to define the `__SANITIZE_ADDRESS__` explicitly.
> Should be found before integrating this PR.

@afshin-zafari , could you respond to this?

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PR Review Comment: https://git.openjdk.org/jdk/pull/27685#discussion_r2493646501