fix #14574, cp on files >2GB

Author: JeffBezanson

base/file.jl

@@ -746,8 +746,14 @@ function sendfile(src::AbstractString, dst::AbstractString)
         dst_file = open(dst, JL_O_CREAT | JL_O_TRUNC | JL_O_WRONLY, filemode(src_file))
         dst_open = true
 
-        bytes = filesize(stat(src_file))
-        sendfile(dst_file, src_file, Int64(0), Int(bytes))
+        bytes = Int(filesize(stat(src_file)))
+        offs = Int64(0)
+        while true
+            nsent = sendfile(dst_file, src_file, offs, bytes)
+            bytes -= nsent
+            offs += nsent
+            bytes <= 0 && break
+        end
     finally
         if src_open && isopen(src_file)
             close(src_file)

base/filesystem.jl

@@ -106,10 +106,10 @@ end
 function sendfile(dst::File, src::File, src_offset::Int64, bytes::Int)
     check_open(dst)
     check_open(src)
-    err = ccall(:jl_fs_sendfile, Int32, (OS_HANDLE, OS_HANDLE, Int64, Csize_t),
-                src.handle, dst.handle, src_offset, bytes)
-    uv_error("sendfile", err)
-    nothing
+    result = ccall(:jl_fs_sendfile, Int32, (OS_HANDLE, OS_HANDLE, Int64, Csize_t),
+                   src.handle, dst.handle, src_offset, bytes)
+    uv_error("sendfile", result)
+    return Int(result)  # bytes written
 end
 
 function unsafe_write(f::File, buf::Ptr{UInt8}, len::UInt, offset::Int64=Int64(-1))