Mmap: fix grow! for non file IOs

base/iostream.jl

@@ -230,8 +230,8 @@ end
 function filesize(s::IOStream)
     sz = @_lock_ios s ccall(:ios_filesize, Int64, (Ptr{Cvoid},), s.ios)
     if sz == -1
-        err = Libc.errno()
-        throw(IOError(string("filesize: ", Libc.strerror(err), " for ", s.name), err))
+        # if `s` is not seekable `ios_filesize` can fail, so fall back to slower stat method
+        sz = filesize(stat(s))
     end
     return sz
 end

stdlib/Mmap/src/Mmap.jl

@@ -45,6 +45,7 @@ Anonymous() = Anonymous("",false,true)
 Base.isopen(::Anonymous) = true
 Base.isreadable(::Anonymous) = true
 Base.iswritable(a::Anonymous) = !a.readonly
+Base.isfile(::Anonymous) = true
 
 # const used for zeroed, anonymous memory
 gethandle(io::Anonymous) = INVALID_OS_HANDLE
@@ -86,6 +87,8 @@ grow!(::Anonymous,o::Integer,l::Integer) = return
 function grow!(io::IO, offset::Integer, len::Integer)
     pos = position(io)
     filelen = filesize(io)
+    # If non-regular file skip trying to grow since we know that will fail the ftruncate syscall
+    filelen == 0 && !isfile(io) && return
     if filelen < offset + len
         failure = ccall(:jl_ftruncate, Cint, (Cint, Int64), fd(io), offset+len)
         Base.systemerror(:ftruncate, failure != 0)
@@ -218,7 +221,7 @@ function mmap(io::IO,
     # platform-specific mmapping
     @static if Sys.isunix()
         prot, flags, iswrite = settings(file_desc, shared)
-        if requestedSizeLarger
+        if isfile(io) && requestedSizeLarger  # add a condition to this line to ensure it only checks files
             if iswrite
                 if grow
                     grow!(io, offset, len)