RFR: 8318696: Do not use LFS64 symbols on Linux [v3]

[Kim Barrett]

On Fri, 19 Jan 2024 06:47:39 GMT, Sam James <duke at openjdk.org> wrote:

>> The LFS64 symbols provided by glibc are not part of any standard and were gated behind -D_LARGEFILE64_SOURCE in musl 1.2.4 (to be removed in 1.2.5). This commit replaces the usage of LFS64 symbols with their regular counterparts and defines -D_FILE_OFFSET_BITS=64, ensuring that functions will always act as their -64 variants on glibc.
>
> Sam James has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add message for assert
>   
>   Not all C++ stds implement it w/o.

Consider (perhaps in a separate PR) forbidding the use of the xxx64 functions,
using FORBID_C_FUNCTION (from compilerWarnings.hpp &etc).  I think it would be
done in globalDefinitions_gcc.hpp, and probably conditional on
_LARGEFILE64_SOURCE.

src/hotspot/os/linux/os_linux.cpp line 4252:

> 4250: // otherwise, returns -1 that implies an error
> 4251: jlong os::Linux::sendfile(int out_fd, int in_fd, jlong* offset, jlong count) {
> 4252:   return ::sendfile64(out_fd, in_fd, (off_t*)offset, (size_t)count);

Why is this continuing to use sendfile64, rather than sendfile?

src/hotspot/os/linux/os_linux.cpp line 4936:

> 4934:   {
> 4935:     struct stat buf64;
> 4936:     int ret = ::fstat(fd, &buf64);

Consider s/buf64/buf/.  The 64 suffix looks rather odd now.

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PR Review: https://git.openjdk.org/jdk/pull/16329#pullrequestreview-1832057351
PR Review Comment: https://git.openjdk.org/jdk/pull/16329#discussion_r1458712646
PR Review Comment: https://git.openjdk.org/jdk/pull/16329#discussion_r1458717682