mirror of
https://github.com/matrix-construct/construct
synced 2024-06-02 18:18:56 +02:00
67 lines
2.1 KiB
Markdown
67 lines
2.1 KiB
Markdown
# Module Tree
|
|
|
|
This directory contains dynamically loadable functionality to libircd.
|
|
|
|
#### Approach
|
|
|
|
Unlike most of the module systems found in traditional C 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.
|
|
|
|
##### GLOBAL SYMBOLS
|
|
|
|
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.
|
|
|
|
##### WEAK UNDEFINED SYMBOLS
|
|
|
|
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 definitions are not available because they are in an unloaded module: a C++
|
|
exception is thrown directly from the callsite. We have built this action
|
|
is built into the lookup mechanism of the runtime dynamic linker; none of
|
|
this requires knowledge or effort from developers to use.
|
|
|
|
#### Layout
|
|
|
|
(TODO)
|
|
|
|
## 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.
|