RFR: 8339331: GCC fortify error in vm_version_linux_aarch64.cpp

[Andrew Haley]

On Tue, 10 Dec 2024 03:44:03 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 suppression pragma macro `PRAGMA_DISABLE_GCC_WARNING("-Wnonnull")` to disable 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

src/hotspot/os_cpu/linux_aarch64/vm_version_linux_aarch64.cpp line 191:

> 189:     PRAGMA_NONNULL_IGNORED
> 190:     ssize_t read_sz = ::read(fd, buf, buflen);
> 191:     PRAGMA_DIAG_POP

Does hardening `buf != nullptr` to a `guarantee()` fix it?

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PR Review Comment: https://git.openjdk.org/jdk/pull/22655#discussion_r1877740414