RFR: 8339331: GCC fortify error in vm_version_linux_aarch64.cpp [v2]

[David Holmes]

On Tue, 10 Dec 2024 10:18:13 GMT, SendaoYan <syan at openjdk.org> wrote:

>> Hi all,
>> The file src/hotspot/os_cpu/linux_aarch64/vm_version_linux_aarch64.cpp report nullptr compile warning by gcc14 with fastdebug configure. I think it's false positive, since the statement 'assert(buf != nullptr, "invalid argument");' has make sure the buf should not be nullptr before execute '::read(int, void*, int)'. The call chain is `void VM_Version::initialize_cpu_information(void)` -> `void VM_Version::get_compatible_board(char *buf, int buflen)` -> `static bool read_fully(const char *fname, char *buf, size_t buflen)`, `*buf` is defined as `char  Abstract_VM_Version::_cpu_desc[4096] = {0};` and then right shift 8 bytes, so `*buf` should not be nullptr.
>> This PR use guarantee instead of assert to suppress false positive gcc compile warning to make fastdebug configure make success on linux-aarch64 by gcc14.2.0.
>> Risk is low.
>> 
>> Additional testing:
>> 
>> - [x]  jtreg tests(include tier1/2/3) on linux-x64 with release build
>> - [x]  jtreg tests(include tier1/2/3) on linux-x64 with fastdebug build
>> - [x]  jtreg tests(include tier1/2/3) on linux-aarch64 with release build
>> - [x]  jtreg tests(include tier1/2/3) on linux-aarch64 with fastdebug build
>
> SendaoYan has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use guarantee instead of assert to suppress gcc warnings

It annoys me that we have to add runtime overhead to release builds to suppress this kind of warning. This code only has internal callers, all of which should be known to not pass a null buf, so the assert should suffice here.

But given the very limited use of the affected function I will approve it.

Thanks

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Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/22655#pullrequestreview-2507722870