On 19.07.24 21:27, David E. Wheeler wrote:
I’m trying to understand the standard terms for extension libraries. There seem
too a bewildering number of terms used to refer to a shared object library, for
example:
* LOAD[1]:
* “shared library”
* “shared library file”
* dynamic_library_path[2]:
* “dynamically loadable module”
* xfunc-c[3]:
* “dynamically loadable object”
* “shared library”
* “loadable object”
* “loadable object file”
* “object file”
* “dynamically loaded object file”
* pg_config[5]:
* “object code libraries” (static?)
* “dynamically loadable modules”
* PGXS[4]:
* “MODULES”
* “shared-library objects”
* “shared library”
I think in the POSIX-ish realm, the best term is "dynamically loadable
library". It's a library, because it contains functions you can, uh,
borrow, just like a static library. And it's dynamically loadable, as
opposed to being loaded in a fixed manner at startup time.
Also, the "dl" in dlopen() etc. presumably stands for dynamic-something
load-something.
Libtool uses the term "dlopened module" for this, and the command-line
option is -module.
(https://www.gnu.org/software/libtool/manual/libtool.html#Dlopened-modules)
Meson uses shared_module() for this. (It has shared_library() and
static_library() for things like libpq.)
Things like "object" or "object file" or probably wrong-ish. I
understand an object file to be a .o file, which you can't dlopen directly.
Shared library is semi-ok because on many platforms, link-time shared
libraries (like libpq) and dynamically loadable libraries (like plpgsql)
are the same file format. But on some they're not, so it leads to
confusion.
I think we can unify this around terms like "dynamically loadable
library" and "dynamically loadable module" (or "loaded" in cases where
it's talking about a file that has already been loaded).
