Sven Barth wrote:
/Why/ can't a library be run standalone? We're already at the position
that an executable can decide whether it's been invoked from a shell or
the GUI and behave as appropriate, so why can't it decide whether it's
being run as a program or being initialised as a library?
A library and an application have different entry point signatures. Take
Windows for example. There the entry point for applications is
"procedure EntryPoint; stdcall;" while for DLLs it is "procedure
EntryPoint(aHinstance: PtrInt; aDLLReason: Word; aDLLParam: Pointer);
stdcall;". Additionally the entry point of a DLL is called multiple
times (once the process loads the library, every time a new thread is
created and destroyed and once the process unloads the library) while
the entry point of an application is only called once. Also AFAIK
Windows does not let you run binaries that are flagged as "DLL". That's
the reason why there is a program called "rundll32" ;) [though it
expects an exported function with a certain signature...]
Assuming for a moment that a binary can be built that is basically an
executable but also exports library-style entry points, and which could
be loaded into memory using DynLib or whatever: could the initialisation
function be told to return fast and cleanly if it detected that it
wasn't being run as a program? In that case, the caller could use DynLib
to load it and then invoke a different entry point explicitly to handle
initialisation.
Hypothetical case in which this sort of thing could be useful: if run as
a program the library outputs a .inc or .h file describing its exports.
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
--
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