Module Tolk.Compiler_worker
Compiles in processes of their own.
A worker is a C program, carried by tolk as bytes, that loads a vendor's compiler library and compiles: a library that serialises the compiles of a process, or crashes on a source, then holds or ends a worker's process only. On Linux the program runs from a sealed memory file, which runs where the home directory is mounted noexec; elsewhere from a file named by the program's digest, written aside and renamed into place, in Helpers.cache_dir, or in Filename.get_temp_dir_name if the cache cannot be written, other users can write it, or the system refuses to run a program from it. Such a file runs only if it is a regular file reached through no link, this user's, that no other user can write, without macOS's quarantine, holding the program's bytes; it is checked at each start and written again otherwise. Where another user's file holds the name, as in a shared temporary directory, the program runs from the file written aside, removed when this process exits.
A request is the worker's own fields and source. A reply is ok N\n then N bytes of binary, or error N\n then N bytes of message, whole if and only if it is N bytes past its header. What a worker prints goes to its diagnostics, a file. A worker serves compiles in turn (call). compiler_worker.h holds the worker's side.
type tThe type for workers.
v ~name program is the worker whose executable is program, named name in its files and its errors. Nothing is written until call.
call w library request has a worker of w serving library answer request: one that is idle, or else one it starts, as PROGRAM LIBRARY TEMP PARENT, PARENT this process's pid. A serving worker reads requests, each N\n then N bytes, on its standard input, replies to each on its standard output once it has read it whole, and ends when its input does or when this process ends, killed or not: a worker in a compile that does not return ends then too, within a second. A process forked from this one starts workers of its own: those it inherits are its parent's, and it closes its copies of their descriptors when it first calls with w.
TEMP is a directory of the worker's own in Filename.get_temp_dir_name, made its temporary directory. The worker removes it, with all in it, when it ends as above, but for what a compile creates while the directory is being removed, when this process ends during that compile; this process removes it when it finds the worker ended, so that what a crashed compile leaves goes with it. The directory of a worker killed while idle stays until a call of this process for its library finds it ended, or for good if this process exits first.
A worker is idle between calls, from any domain; there is no limit to their number. On Windows a worker inherits only its own three handles.
It is Ok binary or Error message as the worker replies. A worker that ends without a whole reply, or sends what is no reply, fails the request, with Error saying how it ended then what it printed during the request, and serves no other: the next call starts another. An idle worker that has ended meanwhile is replaced before the request is sent. A worker that replies has what it printed during the request printed on standard error.
A worker that ends never raises SIGPIPE here: requests go to a socket sent to without the signal, or on Windows, which has none, to a pipe.
Raises Failure naming the worker if its program can be written to neither directory, or cannot be started; the failure names each directory's.