# Hacking on MySQL++

If you are going to make any changes to MySQL++, this file has some
hints and commentary you may find helpful.

## Code Repository Access

MySQL++ uses the [Fossil][fsl] [distributed version control
system][dvcs]. See its [quick start guide][fslq] if you are unfamilar
with Fossil.

That Fossil repository is also [mirrored to GitHub][ghm] nightly, but
this is a read-only mirror, meant for use with Git automation tooling.
For example, you could use MySQL++ as a submodule in a larger Git
project via this channel. [Changes to MySQL++](#patches) still must go
go through the Fossil repository.

You must be running Fossil version 2.1 or higher to access the MySQL++
repository. If your operating system includes an older Fossil package,
you will either have to install [an official binary][fslb] or [build
it from source][fsls].

To clone the MySQL++ repository anonymously, say:

    $ fossil clone https://tangentsoft.com/mysqlpp mysqlpp.fossil

If you have a developer account on the MySQL++ Fossil instance, just add
your username to the URL like so:

    $ fossil clone https://username@tangentsoft.com/mysqlpp mysqlpp.fossil

That will get you a file called `mysqlpp.fossil` containing the [abridged
version history][avh] of MySQL++ back to the project's founding.

The repository clone file can be named anything you like. Even the
`.fossil` extension is just a convention, not a requirement.

To "open" the repo clone so you can hack on it, say:

    $ mkdir mysqlpp
    $ cd mysqlpp
    $ fossil open ../mysqlpp.fossil

This two step “clone and open” process may seem weird if you’re used to
Git, but it’s a feature. It means the repository and working directories
are separate, allowing you to create multiple independent checkouts from
a single repo clone. I like a working tree that looks like this:

    ~/museum/                  # Where one keeps fossils, right?
        mysqlpp.fossil
    ~/src/                     # Working tree for software projects
        mysqlpp/               # A directory for each project
            trunk/             # Primary working branch for MySQL++
            v2.3.2-modern/     # Checkout for another branch
            v3.2.3/            # Checkout for a tagged stable release

You check out a branch or tag like so:

    $ cd ~/src/mysqlpp/v3.2.3
    $ fossil open ~/museum/mysqlpp.fossil v3.2.3

Fossil will let you make any modifications you like to your local
repository copy. For those with check-in privileges on the upstream
copy, changes get automatically synced with it by default. (If you
prefer Git or Mercurial style two-phase commits, you can say `fossil set
autosync off`, then later say `fossil push` after making one or more
checkins.) If you don't have commit capability on the central repository
server, checkins just modify your local repository clone. If you do such
checkins on a branch, you don’t need to worry about conflicts when
pulling down upstream changes into your local clone.

Developers are expected to make all changes that affect the libary's
API, ABI, or behavior on a branch, rather than check such changes
directly into the trunk. Once we have discussed the change on the
[forum][for] and resolved any isssues with the experimental branch, it
will be merged into the trunk.

Creating a branch in Fossil is scary-simple, to the point that those
coming from other version control systems may ask, "Is that really all
there is to it?" Yes, really, this is it:

    $ fossil checkin --branch new-branch-name

That is to say, you make your changes as you normally would; then when
you go to make the first checkin, you give the `--branch` option to put
the changes on a new branch, rather than add them to the same branch the
changes were made against. Every subsequent checkin without a `--branch`
option gets checked in as the new tip of that branch.

If you’re creating a branch that will probably live a long enough time
that you’ll want to return to trunk one or more times while that branch
lives, you might follow the above command with a sequence like this:

    $ fossil update trunk           # return working dir to tip-of-trunk
    $ mkdir ../new-branch-name
    $ cd ../new-branch-name
    $ fossil open ~/museum/mysqlpp.fossil new-branch-name

Now you can bounce back and forth between trunk and your new branch with
a simple `cd` command, rather than switching in place, as is typical
with Git. This style of work avoids invalidating build system outputs,
and it makes it possible to switch branches without checking in or
stashing your work on the other branch first.

[avh]:  https://tangentsoft.com/mysqlpp/wiki?name=Abridged+Version+History
[dvcs]: http://en.wikipedia.org/wiki/Distributed_revision_control
[for]:  https://tangentsoft.com/mysqlpp/froum/
[fsl]:  http://fossil-scm.org/
[fslb]: http://fossil-scm.org/fossil/uv/download.html
[fslq]: http://fossil-scm.org/fossil/doc/trunk/www/quickstart.wiki
[fsls]: http://fossil-scm.org/fossil/doc/trunk/www/build.wiki
[ghm]:  https://github.com/tangentsoft/mysqlpp

## Bootstrapping the Library

When you check out MySQL++ from Fossil, there are a lot of things
"missing" as compared to a distributed tarball, because the Fossil
repository contains only source files, no generated files.  The
process that turns a fresh MySQL++ repository checkout into
something you can build and hack on is called bootstrapping.

Boostrapping is best done on a modern Unix type platform: Linux, OS
X, BSD, Solaris...any version released since 2005 or so. It's
possible to do it on Windows, but much harder; we cover the options
below in a separate section.

Two of the tools you need to do this are commonly available on Unixy
systems, at least as an option: Perl 5, and GNU Autoconf 1.59 or higher.
If they're not installed, you can probably run your system's package
manager to install suitable versions.

There's a third tool you'll need to bootstrap MySQL++ called
[Bakefile][bf]. The syntax used in `mysql++.bkl` requires at least
Bakefile 0.2.5 or higher, which in turn requires Python 2.3 or higher to
run. You may require a newer version of Bakefile to support newer OSes
and Python versions; we've tested with versions up to 0.2.11
successfully.

Do not use any of the Bakefile 1.x versions: it’s an incompatible
change, and we currently have no intention to switch from Bakefile 0.x.

Once you have all the tools in place, you can bootstrap MySQL++ with a
Bourne shell script called `bootstrap`, which you get as part of the
Fossil checkout. It's fairly powerful, with many options.  For most
cases, it suffices to just run it without any arguments:

    $ ./bootstrap

For more unusual situations, here's the complete usage:

    $ ./bootstrap [no{doc,ex,lib,opt}] [pedantic] [bat] [configure flags]

Arguments:

*   `nodoc`

    The documentation won't be considered a prerequisite for building
    the distribution tarball. This is useful on systems where the
    documentation doesn't build correctly, and you only need to make a
    binary RPM. That process requires a tarball, but doesn't need the
    documentation. Don't distribute the tarball or SRPM that results, as
    they are no good for any other purpose.

*   `noex`

    The generated `Makefiles` and project files won't try to build any of
    the examples.

*   `nolib`

    The generated `Makefiles` and project files won't try to build the
    MySQL++ library.

*   `nomaint`

    Turn off "maintainer mode" stuff in the build. These are features
    used only by those building MySQL++ from Fossil. The `dist` build
    target uses this when creating the tarball, because it reduces the
    build time somewhat.

*   `noopt`

    Compiler optimization will be turned off. (This currently has no
    effect on the generated MinGW Makefile or the Visual C++ project
    files.)

*   `pedantic`

    Turns on all of GCC's warnings and portability checks.  We use this
    as part of our [release process](./RELEASE-CHECKLIST.txt).

*   `bat`

    Runs `bootstrap.bat` via `cmd.exe` for you, passing along equivalent
    options to any of the "*no*" options you give before it.

    Only the "*no*" options above have an effect on the generated build
    system files when you give "`bat`".  In particular, the files
    generated by `bootstrap.bat` make no distinction between "pedantic"
    and normal builds.

    Passing `bat` stops all command line processing in the `bootstrap`
    script, so if you also pass some of the other options, "`bat`" must
    be last.
    
    The `bootstrap.bat` script is useful only when you intend to build
    MySQL++ with MinGW or Visual C++, and you are using Cygwin only as a
    command line environment.  If you intend to build MySQL++ with
    Cygwin's GCC toolchain, you must not give this option, else you will
    not end up with the necessary build system files.

    One advantage of this feature is that the commands necessary to
    achieve a given effect with `bootstrap.bat` when run via `bootstrap`
    are shorter than when you run the batch file directly.

    Another advantage is that this low-strength version of the bootstrap
    script runs faster than the full-strength form, because it produces
    fewer files.

    Finally, running `bootstrap.bat` indirectly like this lets you avoid
    using `cmd.exe`, a command shell greatly inferior to any of those
    available for Cygwin.

*   `configure` script options

    As soon as the bootstrap script sees an option that it doesn't
    understand, it stops processing the command line.  Any subsequent
    options are passed to the `configure` script. See
    [README-Unix.txt][rmu] for more on `configure` script options.

[bf]:  http://bakefile.org/
[rmu]: https://tangentsoft.com/mysqlpp/file/README-Unix.txt

## Bootstrapping the Library Using Only Windows

The thing that makes bootstrapping on Windows difficult is that one of
the required steps uses a Unix-centric tool, Autoconf.  This section
gives alternatives for either getting Autoconf working on Windows or
avoiding the need for it.

The thing Autoconf does that's relevant to Windows builds of MySQL++
is that it substitutes the current MySQL++ version number into several
source files. This allows us to change the version number in just one
place — `configure.ac` — and have it applied to all these other places.
Until you do this step, a Fossil checkout of MySQL++ won't build,
because these files with the version numbers in them won't be generated.


### Option 1: Copy the generated files over from a released version

Only one of these generated files is absolutely critical to allowing
MySQL++ to build: `lib/mysql++.h`. So, the simplest option you have to
bootstrap MySQL++ entirely on Windows is to copy `lib/mysql++.h` over
from a released version of MySQL++. While you're doing that, you might
copy over the other such generated files:

    install.hta
    mysql++.spec
    doc/userman/userman.dbx
    lib/Doxyfile

Having done that, you can complete the bootstrapping process by running
`bootstrap.bat`. It has the same purpose as the Bourne shell script
described [above](#bootstrap), but with a different and simpler usage:

    C:\> bootstrap.bat [bakefile-options]

Any options passed are passed as-is to Bakefile. This is normally used
to pass `-D` options to affect the generated build system output files.


### Option 2: Cygwin

If you'd like to hack on MySQL++ entirely on Windows and have all the
build freedoms enjoyed by those working on Unixy platforms, the simplest
solution is probably to [install Cygwin][cyg]. It doesn’t matter whether
you use the 32-bit or 64-bit version, for our purposes here.

While in the Cygwin setup program, you will have to add the Autoconf and
Perl 5 packages, which aren't installed in Cygwin by default.  Autoconf
is in the Devel category, and Perl 5 in the Interpreters category.

You will also need to install the native Windows binary version of
[Bakefile](http://bakefile.org/).  Don't get the source version and try
to build Bakefile under Cygwin; it won't work. The Windows binary
version of Bakefile includes an embedded version of Python, so you won't
need to install Cygwin's Python.

Having done all this, you can follow the Unix bootstrapping
instructions in the previous section.

[cyg]: http://cygwin.com/


### Option 3: Windows Subsystem for Linux (WSL)

If you’re on Windows 10, you have the option of [installing WSL][wsl], a
lightweight Linux kernel and user environment that runs atop Windows.
This is fundamentally different technology than Cygwin, but the
user-level effect of it is the same as far as MySQL++’s build system
goes.

Assuming you use the default Ubuntu enviroment atop WSL, the [standard
bootstrapping process](#bootstrap) applies, after you install the needed
tools:

    $ apt install bakefile build-essential perl libmysqlclient-dev

[wsl]: https://docs.microsoft.com/en-us/windows/wsl/install-win10


### Option 4: ["Here's a nickel, kid, get yourself a better computer."][dc]

Finally, you might have access to a Unixy system, or the ability to set
one up. You don't even need a separate physical computer, now that
virtual machine techology is free.

Given such a machine, you'd do the Fossil checkout of MySQL++ on that
machine, then bootstrap it there using the instructions in the previous
section, and copy the generated files back to the Windows box.

[dc]: http://tomayko.com/writings/that-dilbert-cartoon


## On Manipulating the Build System Source Files

One of the things the bootstrapping system described [above](#bootstrap)
does is produces various types of project and make files from a small
number of source files. This system lets us support many platforms
without having to maintain separate build system files for each
platform.

[Bakefile](http://bakefile.org/) produces most of these project and make
files from a single source file called [`mysql++.bkl`][bkl].

Except for small local changes, it's best to change `mysql++.bkl` and
"re-bake" the project and make files rather than change those files
directly. You can do this with the bootstrap scripts covered above. On
Windows, if all you've changed is `mysql++.bkl`, you can use
`rebake.bat` instead, which doesn't try to do as much as
`bootstrap.bat`.

Bakefile produces finished project files for Visual C++ and Xcode and
finished `Makefiles` for MinGW. It also produces `Makefile.in`, which is
input to GNU Autoconf along with `configure.ac` and `config/*`. You may
need to change these latter files in addition to or instead of
`mysql++.bkl` to get the effect you want.  Running bootstrap
incorporates changes to all of these files in the GNU Autoconf output.

While Bakefile's documentation isn't as comprehensive as it
ought to be, you can at least count on it to list all of the
available features. So, if you can't see a way to make Bakefile
do something, it's likely it just can't do it. Bakefile is a
high-level abstraction of build systems in general, so it'll never
support all the particulars of every odd build system out there.

[bkl]: https://tangentsoft.com/mysqlpp/file/mysql%2B%2B.bkl

## Submitting Patches

If you wish to submit a patch to the library, it’s probably simplest to
paste it into a [forum post][for], if it’s small. If it’s large, put it
in Pastebin or similar, then link to it from a forum post.  We want
patches in unified diff format.

We will also accept trivial patches not needing discussion as text
or attachments to [a Fossil ticket][tkt].

The easiest way to get a unified diff is to check out a copy of the
current MySQL++ tree [as described above](#repo). Then make your change,
`cd` to the MySQL++ root directory, and ask Fossil to generate the patch
for you:

    $ fossil diff > mychange.patch

If your patch adds new files, moves files, or needs to be understood in
terms of multiple checkins, it's best to do that work on a [private
local branch](#private), then send a [bundle][fb] instead of a patch.

If you've sent patches to MySQL++ before and don't have a Fossil
developer login, another alternative is to ask for a login before you
begin work so that your changes are automatically sync'd to the main
Fossil repository as you work, so you don't have to send bundles or
patch files. We generally don't refuse such requests if you've already
proven your ability to work productively with the MySQL++ project.

If you're making a patch against a MySQL++ distribution tarball, then
you can generate a patch this way:

    $ diff -ruN mysql++-olddir mysql++-newdir > mychange.patch

The `diff` command is part of every Unix and Linux system, and should be
installed by default. If you're on a Windows machine, GNU diff is part
of [Cygwin](http://cygwin.com/). Fossil is also available for all of
these systems. There are no excuses for not being able to make unified
diffs. :)

Although MySQL++ does have a [GitHub mirror][ghm], we do not acccept PRs
via that channel, because the mirror is read-only. You can still send us
a PR through GitHub, but realize that what’s going to happen on the back
end is that we’ll generate a patch and apply it to the Fossil repo by
hand, then update the mirror, so you won’t get GitHub credit for the PR.
Sorry; there’s no easy way for this mirroring system to accept
contributions back the other direction. If you want credit for the
commit, ask us for an account on the Fossil repo, and commit it there
instead.

[fb]:  http://fossil-scm.org/fossil/help?cmd=bundle
[tkt]: https://tangentsoft.com/mysqlpp/tktnew


## The MySQL++ Code Style

Every code base should have a common code style. Love it or
hate it, here are MySQL++'s current code style rules:


### Source Code

File types: `ac`, `cpp`, `h`, `in`, `m4`, `pl`

-   Tabs for indents, size 4

-   Unix line endings. Any decent programmer's editor can cope with
    this, even on Windows.

-   C/C++ rules:

    -   Base whitespace style is AT&Tish: K&R/Stroustrup, plus a little
        local spice. If you have the indent(1) program, the command is:

            indent -kr -nce -cli4 -ss -di1 -psl -ts4 FILES...

        That is, don't cuddle else, indent case statement labels, space
        before semicolon with empty loop body, no extra space between a
        variable type and name, return value of function on separate
        line from rest of definition.

    -   Class names are in `CamelCase`, uppercased first letter

    -   Method names are in `all_lower_case_with_underscores()`;
        ditto most other global symbols.

    -   Macro names are in `ALL_UPPERCASE_WITH_UNDERSCORES`

    -   Doxygen comment for all public declarations, unless there is a
        very good reason to keep the thing undocumented.

-   Perl and shell script rules are more or less the same as for C/C++,
    to the extent this makes sense.


### XML/HTML Dialects

File types: `bkl`, `dbx`, `hta`

-   Spaces for indents, size 2. Shallow indents due to the high level of
    nesting occurring in such files, and spaces because they're not as
    annoying at shallow indent levels in editors that don't treat space
    indents like tabs.

-   Unix line endings. Again, these are intended to be viewed in a
    programmer's text editor, which should work with Unix line endings
    no matter the platform.


### Plain Text Files

File types: `txt`

-   Spaces for indents, size 4. Spaces because such files are often
    viewed in Notepad and similarly crippled text editors which use a
    default indent level of 8.

-   DOS line endings, again for the Notepad reason. And on modern Unixy
    platforms, the tools cope with DOS line endings reasonably well.
    Better than the converse, anyway.


When in doubt, mimic what you see in the current code. When still in
doubt, ask on [the forum][for].


## Testing Your Proposed Change

MySQL++ includes a self-test mechanism called `dtest`. It's a Bourne
shell script, run much like `exrun`:

    $ ./dtest [-s server_addr] [-u user] [-p password]

This automatically runs most of the examples, captures the outputs to a
file, and then compares that to a known-good run's outputs, stored in
`bmark.txt`. So, before you submit a patch, run `dtest` to see if
anything has changed. If something has and you can't account for it, it
represents a problem that you'll have to fix before submitting the
patch. If it gives an expected change, remove `bmark.txt`, re-run
`dtest`, and include the `bmark.txt` diffs in your patch. This
communicates to us the fact that you know there are differences and want
the patch evaluated anyway. Otherwise, we are likely to view the change
as a bug.

`dtest` also runs all of the unit tests in `test/*`. The purpose of
`test/*` is different from that of `examples/*`:

-   `test/*` are unit tests: each tests only one MySQL++ class,
    independent of everything else. Because DB access requires several
    MySQL++ classes to cooperate, a unit test never accesses a database;
    hence, no unit test needs DB connection parameters.  We will never
    get 100% code coverage from `test/*` alone.

-   `examples/*` can be thought of as integration tests: they test many
    pieces of MySQL++ working together, accessing a real database
    server. In addition to ensuring that all the pieces work together
    and give consistent results from platform to platform and run to
    run, it also fills in gaps in the code coverage where no suitable
    `test/*` module could be created.

-   `test/*` programs always run silently on success, writing output
    only to indicate test failures. This is because they're usually only
    run via `dtest`.

-   `examples/*` are always "noisy," regardless of whether they succeed
    or fail, because they're also run interactively by people learning
    to use MySQL++.

Patches should include tests if they introduce new functionality or fix
a bug that the existing test coverage failed to catch.  If the test is
noisy, needs DB access, or tests multiple parts of the library at once,
it goes in `examples/*`. If your change affects only one class in
MySQL++ and testing it can be done without instantiating other MySQL++
classes — other than by composition, of course — it should go in
`test/*`.

In general, prefer modifying an existing `examples/*` or `test/*`
program.  Add a new one only if you're introducing brand new
functionality or when a given feature currently has no test at all.

Beware that the primary role the examples is to illustrate points in the
user manual. If an existing example does something similar to what a
proper test would need to do and the test doesn't change the nature of
the example, don't worry about changing the example code. If your test
would change the nature of the example, you either need to do the test
another way, or also submit a change to `doc/userman/*.dbx` that
incorporates the difference.

## Adding Support for a Different Compiler

As described above, MySQL++ uses the Bakefile system for creating
project files and makefiles. This allows us to make changes to a single
set of files, and have the proper changes be made to all generated
project files and makefiles. In the past, we used more ad-hoc systems,
and we'd frequently forget to update individual project files and
makefiles, so at any given time, at least one target was likely to be
broken.

If MySQL++ doesn't currently ship with project files or makefiles tuned
for your compiler of choice, you need to work through the Bakefile
mechanism to add support. We're not willing to do ad-hoc platform
support any more, so please don't ask if you can send us project files
instead; we don't want them.

If you want to port MySQL++ to another platform, we need to be confident
that the entire library works on your platform before we'll accept
patches. In the past, we've had broken ports that were missing important
library features, or that crashed when built in certain ways. Few people
will knowingly use a crippled version of MySQL++, since there are
usually acceptable alternatives.  Therefore, such ports become
maintenance baggage with little compensating value.

## Maintaining a Private Repository

Although Fossil syncs changes back to the [MySQL++ Fossil
repository][home] by default, it is possible to maintain a private copy
that simply pulls changes in occasionally.

The first step is to turn off the auto-sync feature:

     $ fossil set autosync off

Then, I recommend that you make any local changes on a branch:

    ...hack, hack, hack...
    $ fossil ci --branch my-local-branch

After you give the `--branch` option on a checkin, Fossil automatically
switches your local checkout to that branch, so that all further
checkins can be made without the `--branch` option.  To get back to the
trunk, you'd say `fossil up trunk`, but under this workflow, the need
for that will be rare.

When something happens on the official trunk on `tangentsoft.com` that
you want pulled into your private repository, say:

    $ fossil sync
    $ fossil merge trunk

The first command pulls all remote changes into your local clone, but
since those changes don't affect your private branch, you won't see any
immediate change. The second attempts to merge the trunk branch's
changes since the last branch or merge point into your private branch.

Whether the merge is successful or not, Fossil does not immediately
modify your clone, only the working checkout directory. You must then
say `fossil ci` once you're happy with the merge. Until then, all the
usual Fossil commands like `fossil diff` and `fossil status` will help
you come to that decision.

If you ever decide to contribute your private branch to the MySQL++
project, there are a couple of easy ways to achieve that. Ask about it
on [the forum][for] if you find yourself in this situation.

[home]: https://tangentsoft.com/mysqlpp/
