Previously 'process-stderr' would always pass a bytevector of MAX-LEN to
then daemon in the %stderr-read case (i.e., 'import-paths'), instead of
LEN (where LEN <= MAX-LEN).
In practice the extra bytes didn't cause a protocol violation or
anything because they happen at the end of the stream, which typically
contains the canonical sexp of the signature, and the extra zeros were
just ignored.
* guix/serialization.scm (write-bytevector): Add optional 'l' parameter
and honor it.
* guix/store.scm (process-stderr): Pass LEN to 'write-bytevector'.
Ludovic Courtès
39d1e9654c