mirror of
https://github.com/matrix-construct/construct
synced 2024-12-11 08:02:59 +01:00
75 lines
2.8 KiB
Markdown
75 lines
2.8 KiB
Markdown
# IRCd Module Tree
|
|
|
|
This directory contains dynamically loadable functionality to libircd. Many of
|
|
these modules provide essential application functionality, but are not always
|
|
required to be directly linked and loaded into libircd proper. Most application-
|
|
specific functionality (i.e "business logic") is contained in modules within this
|
|
tree.
|
|
|
|
#### Layout
|
|
|
|
The `modules/` directory tree is primarily shaped the same as the HTTP resource
|
|
tree in which most of its modules register themselves in.
|
|
|
|
Note that the installation layout is not the same as the development source
|
|
layout (i.e in git). Upon installation, the module tree is collapsed into a
|
|
single directory and installed into
|
|
`$prefix/lib/modules/construct/$directory_$module.so`; where directories are
|
|
replaced by underscores in the final `SONAME`. this may be subject to
|
|
improvement.
|
|
|
|
#### Approach
|
|
|
|
Unlike most of the module systems found in traditional free software projects,
|
|
our approach is oriented around *global symbol* availability to the address
|
|
space rather than explicit imports from self-contained modules. This direction
|
|
is made viable by C++ and advances in the compiler and linker toolchains. The
|
|
result is significantly simpler and more convenient for developers to work with.
|
|
|
|
- Modules are loaded with `RTLD_GLOBAL` on both posix and windows platforms.
|
|
Use of C++ namespaces, visibility attributes, `STB_GNU_UNIQUE`, etc are
|
|
adequate to make this modernization.
|
|
|
|
- All project code is built to silently weaken undefined symbols. This means
|
|
a complicated interface declared in a header, like a class interface with
|
|
public and private and static members -- typical in C++ -- can be included
|
|
by itself into any part of the project without knowing where the definitions
|
|
of that interface are until they are *first used* at runtime. If said
|
|
definitions are not available because they are in an unloaded module, a C++
|
|
exception is thrown directly from the callsite.
|
|
|
|
## Getting started
|
|
|
|
The header `mods/mapi.h` is specific to modules and included for modules in
|
|
addition to the core `ircd.h`. Both of these are included automatically
|
|
via the compiler's command-line and the developer does not have to `#include`
|
|
either in the module.
|
|
|
|
1. Every loadable module requires a static `ircd::mapi::header` with the explicit
|
|
name of `IRCD_MODULE`. This is an object which will be sought by the module
|
|
loader in libircd.
|
|
|
|
```
|
|
// Example of a trivial module
|
|
|
|
ircd::mapi::header
|
|
IRCD_MODULE
|
|
{
|
|
"My Module", []
|
|
{
|
|
puts("hi\n");
|
|
}
|
|
};
|
|
|
|
```
|
|
|
|
2. Add an `_la_SOURCES` entry for your module in the appropriate place in
|
|
Makefile.am.
|
|
|
|
3. Add the module `.la` name to the appropriate LTLIBRARIES list
|
|
in Makefile.am.
|
|
|
|
4. At this time, most modules are listed explicitly in `ircd/m.cc` to
|
|
provide a strict load and unload ordering based on dependency. Note that
|
|
if the module is not `m::` related there may be similar lists for other
|
|
subsystems.
|