construct/doc/BUILD.md

## BUILD (standalone)

##### Compatibility Primer

This section is intended to allow building with dependencies that have not
made their way to mainstream systems. Important notes that may affect you:

- GCC: Ubuntu Xenial (16.04) users must use a PPA to obtain GCC-7 or greater; don't
forget to `export CXX=g++-7` before running `./configure` on that system.

- Boost: The required version is available through `apt` as `boost-all-dev` on
Ubuntu Cosmic (18.10). All earlier releases (including 18.04 LTS) can configure
with `--with-included-boost` as instructed below.

- ~~RocksDB: The required version is available through `apt` as `librocksdb-dev` on
Ubuntu Disco (19.04). All earlier releases (including 18.04 LTS) can configure
with `--with-included-rocksdb` as instructed below.~~

- RocksDB: At this time we advise **all users** including those on 19.04 to
configure with `--with-included-rocksdb` until regressions in your RocksDB
package have been fixed.

##### Installation Primer

A general overview of what construct will build and install is given here. At
this time it is suggested to supply `./configure` with a `--prefix` path,
especially for development. Example `--prefix=~/.local/`.

- Binary executable `$prefix/bin/construct`
- Shared library `$prefix/lib/libircd.so`
- Shared library modules `$prefix/lib/modules/construct/*.so`
- Header files `$prefix/include/ircd/*`
- Read-only shared assets `$prefix/share/construct/*`
- Database directory may be established at `$prefix/var/db/construct/`

```
Do not set your `--prefix` path to a directory inside your git repository or
an invocation of `git clean` will erase your database in $prefix/var/db/.
```

#### STANDALONE BUILD PROCEDURE

```
./autogen.sh
./configure --prefix=$PWD/build --with-included-boost --with-included-rocksdb
make install
```

> The `--with-included-*` will fetch, configure **and build** the dependencies included
as submodules. Please read the compatibility primer first to understand which options
you need or don't need on your system.


### Additional build options

#### Debug mode

```
--enable-debug
```
Full debug mode. Includes additional code within `#ifdef RB_DEBUG` sections.
Optimization level is `-Og`, which is still valgrind-worthy. Debugger support
is `-ggdb`. Log level is `DEBUG` (maximum). Assertions are enabled. No
sanitizer instrumentation is generated by default in this mode.


#### Generic mode binary (for distribution packages)

Construct developers have set the default compilation to generate native
hardware operations which may only be supported on very specific targets. For
a generic mode binary, package maintainers may require this option.

```
--enable-generic
```
Sets `-mtune=generic` as `native` is otherwise the default.


#### Compact mode (experimental)

```
--enable-compact
```
Create the smallest possible resulting output. This will optimize for size
(if optimization is enabled), remove all debugging, strip symbols, and apply
any toolchain-feature or #ifdef in code that optimizes the output size.

_This feature is experimental. It may not build or execute on all platforms
reliably. Please report bugs._


#### Manually enable assertions

```
--enable-assert
```
Implied by `--enable-debug`. This is useful to specifically enable `assert()`
statements when `--enable-debug` is not used.


#### Manually enable optimization

```
--enable-optimize
```
This manually applies full release-mode optimizations even when using
`--enable-debug`. Implied when not in debug mode.


#### Disable third-party dynamic allocator libraries

```
--disable-malloc-libs
```
`./configure` will detect alternative `malloc()` implementations found in
libraries installed on the system (jemalloc/tcmalloc/etc). Construct developers
may enable these to be configured by default, if detected. To always prevent
any alternative to the default standard library allocator specify this option.


#### Enable third-party dynamic allocator libraries

Currently:

```
--enable-jemalloc
```

`./configure` will detect alternative `malloc()` implementations found in
libraries installed on the system (jemalloc/tcmalloc/etc). Construct developers
may not enable these to be configured by default, falling back on the default
allocator. To always use one of the alternative allocators use one option here.


#### Logging level

```
--with-log-level=
```
This manually sets the level of logging. All log levels at or below this level
will be available. When a log level is not available, all code used to generate
its messages will be entirely eliminated via *dead-code-elimination* at compile
time.

The log levels are (from logger.h):
```
7  DEBUG      Maximum verbosity for developers.
6  DWARNING   A warning but only for developers (more frequent than WARNING).
5  DERROR     An error but only worthy of developers (more frequent than ERROR).
4  INFO       A more frequent message with good news.
3  NOTICE     An infrequent important message with neutral or positive news.
2  WARNING    Non-impacting undesirable behavior user should know about.
1  ERROR      Things that shouldn't happen; user impacted and should know.
0  CRITICAL   Catastrophic/unrecoverable; program is in a compromised state.
```

When `--enable-debug` is used `--with-log-level=DEBUG` is implied. Otherwise
for release mode `--with-log-level=INFO` is implied. Large deployments with
many users may consider lower than `INFO` to maximize optimization and reduce
noise.