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# copy-file-range.m4
dnl Copyright 2019-2021 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
AC_DEFUN([gl_FUNC_COPY_FILE_RANGE],
[
AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
dnl Persuade glibc <unistd.h> to declare copy_file_range.
AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
dnl Use AC_LINK_IFELSE, rather than AC_CHECK_FUNCS or a variant,
dnl since we don't want AC_CHECK_FUNCS's checks for glibc stubs.
dnl Programs that use copy_file_range must fall back on read+write
dnl anyway, and there's little point to substituting the Gnulib stub
dnl for a glibc stub.
AC_CACHE_CHECK([for copy_file_range], [gl_cv_func_copy_file_range],
[AC_LINK_IFELSE(
[AC_LANG_PROGRAM(
[[#include <unistd.h>
]],
[[ssize_t (*func) (int, off_t *, int, off_t, size_t, unsigned)
= copy_file_range;
return func (0, 0, 0, 0, 0, 0) & 127;
]])
],
[gl_cv_func_copy_file_range=yes],
[gl_cv_func_copy_file_range=no])
])
if test "$gl_cv_func_copy_file_range" != yes; then
HAVE_COPY_FILE_RANGE=0
fi
])
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