configure: Use AC_SYS_LARGEFILE

[orbea]

With musl-1.2.4 LFS support is being disabled and will later be entirely removed where it is expected to use off_t and lseek rather than off64_t and lseek64.

With glibc these types are also obsolete where it is expected to use the _FILE_OFFSET_BITS define where off_t and lseek will become 64-bit compatible versions when needed. This is set by AC_SYS_LARGEFILE.

[Oleksiy-Yakovenko]

Merging this would break compatibility with 32 bit systems, where lseek is 32 bit.

[orbea]

@Oleksiy-Yakovenko Are you saying deadbeef needs a 64-bit lseek even on 32-bit systems? Or am I not understanding? Unfortunately I do not have any 32-bit hardware to test.

[Oleksiy-Yakovenko]

Yes, lseek64 works on 32 bit systems to seek in large files which are larger than 4GB

[orbea]

Perhaps it would be better to define _FILE_OFFSET_BITS=64 unconditionally?

[Oleksiy-Yakovenko]

I checked the docs, and it seems like adding AC_SYS_LARGEFILE should take care of 64 bit file offsets on 32 bit systems as well, but it needs to be tested before merging. (I'll try to find time for this)

[orbea]

@Oleksiy-Yakovenko Any chance you had time to investigate this yet?

[Oleksiy-Yakovenko]

I haven't, and I'm not sure whether I will. Let's assume that it works as it should. There are not that many 32bit users, if they will complain we'll revert.