• Simon Marlow's avatar
    Change the way module initialisation is done (#3252, #4417) · a52ff761
    Simon Marlow authored
    Previously the code generator generated small code fragments labelled
    with __stginit_M for each module M, and these performed whatever
    initialisation was necessary for that module and recursively invoked
    the initialisation functions for imported modules.  This appraoch had
     - FFI users had to call hs_add_root() to ensure the correct
       initialisation routines were called.  This is a non-standard,
       and ugly, API.
     - unless we were using -split-objs, the __stginit dependencies would
       entail linking the whole transitive closure of modules imported,
       whether they were actually used or not.  In an extreme case (#4387,
       #4417), a module from GHC might be imported for use in Template
       Haskell or an annotation, and that would force the whole of GHC to
       be needlessly linked into the final executable.
    So now instead we do our initialisation with C functions marked with
    __attribute__((constructor)), which are automatically invoked at
    program startup time (or DSO load-time).  The C initialisers are
    emitted into the stub.c file.  This means that every time we compile
    with -prof or -hpc, we now get a stub file, but thanks to #3687 that
    is now invisible to the user.
    There are some refactorings in the RTS (particularly for HPC) to
    handle the fact that initialisers now get run earlier than they did
    The __stginit symbols are still generated, and the hs_add_root()
    function still exists (but does nothing), for backwards compatibility.
CLabel.hs 37.2 KB