Date: Mon, 19 Aug 2019 20:56:35 -0400 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: [PATCH] Add copy_file_range system call On Mon, Aug 19, 2019 at 11:41:14PM +0000, Árni Dagur wrote: > This patch was based on commit 53147f9, which added splice and vmsplice. > --- > The function signature in the glibc manpage specifies `loff_t` instead > of `off_t`, for both `copy_file_range` and `splice`. In musl, however, > the function signature for `splice` specifies `off_t`, so I did the > same here. I'm not an experienced C programmer, so that may have been > wrong. I think this looks ok. Regarding loff_t vs off_t, loff_t is the kernel's API type for functions that take a 64-bit offset unconditionally rather than glibc providing 32-bit off_t and 64-bit off_t versions of them. This is gratuitous for musl where off_t is always 64-bit. We provide loff_t as a macro that expands to off_t, but even if it were a typedef the types woule be the same type, so it's fine to use off_t here, and I think it's the cleanest and most consistent with what we're doing elsewhere even if it's not textually the same as the man page. > include/unistd.h | 1 + > src/linux/copy_file_range.c | 8 ++++++++ > 2 files changed, 9 insertions(+) > create mode 100644 src/linux/copy_file_range.c > > diff --git a/include/unistd.h b/include/unistd.h > index 9485da7a..00cc7042 100644 > --- a/include/unistd.h > +++ b/include/unistd.h > @@ -188,6 +188,7 @@ char *get_current_dir_name(void); > int syncfs(int); > int euidaccess(const char *, int); > int eaccess(const char *, int); > +ssize_t copy_file_range(int fd_in, off_t *off_in, int fd_out, off_t *off_out, size_t len, unsigned flags); > #endif Is there a reason for the choice to put it in unistd.h? Similar functions seem to have gone in fcntl.h. unistd.h does not make the loff_t type available which could be problematic to callers using it, since they really should (for API compatibility) be declaring the objects whose addresses they pass as loff_t. If glibc does it here and exposes loff_t in unistd.h we might need to consider doing that too with _GNU_SOURCE. Rich
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