Whereto put "plugins" in linux - c++

I am currently developing/hacking an image analyzing/transforming tool.
The filters therein will be loaded at runtime using dlopen&co.
My question is where do *nix tools usually put plugins (*.so files) when installed?
bin/program
lib/program/plugins/thisandthat.so
maybe?
Secondly how do I use it and where do I put it during development without installing it. (this is probably the tricky part)
I want to avoid shell-scripts if possible.
thanks in regard
Ronny

Usually /usr/lib/programmname should be a good spot
During development I'd create a command line paramter to specify the plugin search path and just leave the plugins in the build-dir for example.

Consider:
/usr/lib/program/*.so

A good guide for choosing is Filesystem Hierarchy Standard.
Most Linux distribuitions use this standard.
Here is a very short summary.
Place application binary in:
/usr/bin/progname, /usr/local/bin/progname or /opt/progname
Place plugins or library files in:
/usr/lib/progname, /usr/local/lib/progname or /opt/progname/lib
Place host configuration for the application in:
/etc/progname or /etc/opt/progname
Place user configuration in:
$HOME/.progname
Place application manual page in:
/usr/shar/man/man1/
There is separate hierachy for /var. As an example use /var/log/progname for logging.
In responce to caf's comment. I find it very usefull to choose target directory at compile time. Using a $PREFIX also makes it easy to separate devellopment build's from shippment.
Most use /usr/progname, /usr/lib/progname and /etc/progname

Do not forget:
$HOME/.program/

The layout seems sensible. You can, for instance, look in current directory, look up environment variable or command line switch during development. It depends on the details of your development environment and workflow.

Related

Where to store resources for C++ program on linux

This question says the best place to store settings in linux is in ~/.config/appname
The program I'm writing needs to use a 99MB .dat file for recognizing facial landmarks, embedding it in the binary doesn't seem like a good idea.
Is there some default place to store resources on linux? currently it's just in the directory next to the executable, but this requires that the program is run with the current directory being the directory it's located in.
What's the best way to deal with resources like this on linux? (that could potentially be cross platform with at least OSX)
You should take a look at the Filesystem Hierarchy Standards. Depending on the data (will it change, is it constant across all installations, etc) the path where it gets placed will change based on the standards.
In general:
/usr/lib/program: includes object files, libraries, and internal binaries for an application
/usr/share/program: for all read-only architecture independent data files
/var/lib/program: holds state information pertaining to an application or the system
Those seem like pretty good places to start, and you can check the documentation to see if your app falls into one of those categories.
If the file is specific to the user running the app, it should be in a subdir of ~/ but AFAIK there's no standard, and the best choice depends much on the file type/usage. If it should be visible to the user via GUI, you could use ~/Desktop or ~/Downloads. If it's temporary, you can use ~/tmp or ~/var/tmp.
If it's not specific, you should place it in a subdir of /var. Again, the exact subdir may depend on its kind and other factors.

Linked directory not found

I have following scenario:
The main software I wrote uses a database created by a simulator. This database is around 10 GB big at the moment, so I want to keep only one copy of that data per system.
Assuming I have following projects:
Main Software using the data, located at /SimData
DLL using the data for debugging, searching for data at /SimData
Debugging tool to parse the image database, searching for the data at /SimData
Since I do not want to have all those programs have their own copy of SimData (not only to decrease place used, but also to ensure that all Simulation data used is always up to date for all programs).
I created for the DLL and Debugging Utility a link named SimData to MainSoftware/SimData, but when opening a file with "SimData\MyFile.data" it cannot find it, only the MainSoftware with the ACTUAL SimData folder can find it.
How can I use the MainSoftware/SimData folder without setting absolute paths?
This is on Windows 7 x64
I agree with Peter about adding the DB location as a configurable parameter. A common place to store that is in the registry.
however, If you want to create links that will be recognized by your software, try hardlinks. . fsutil should do the trick as described here.
You need a way to configure the database location. You could use an INI or other configuration file, or a registry setting, or a command-line input, or an environment variable. Or You could write your program to search a directory hierarchy... for example, if the various modules are usually siblings of each other in your directory tree, you could search for SimData/MyFile.data, ../SimData/MyFile.data, ../../MainSoftware/SimData/Myfile.data, and use the first one found.
Which answer is the "right one" depends on your situation.

Building a Native Client app from nothing

What does it take to build a Native Client app from scratch? I have looked into the documentation, and fiddled with several apps, however, I am now moving onto making my own app and I don't see anything related to creating the foundation of a native client app.
Depending on the version of the SDK you want to use, you have a couple of options.
Pepper 16 and 17: use init_project.py or use an example as a starting point
If you are using pepper_16 or pepper_17, you will find a Python script init_project.py in the project_templates in the SDK. It will setup up a complete set of files (.cc, .html, .nmf) with comments indicating where you need to add code. Run python init_project.py -h to see what options it accepts. Additional documentation can be found at https://developers.google.com/native-client/pepper17/devguide/tutorial.
Pepper 18 and newer: use an example as the starting point
If you are using pepper_18 or newer, init_project.py is no longer included. Instead you can copy a very small example from the examples directory (e.g., hello_world_glibc or hello_world_newlib for C or hello_world_interactive for C++) and use that as a starting point.
Writing completely from scratch
If you want to write your app completely from scratch, first ensure that the SDK is working by compiling and running a few of the examples. Then a good next step is to look at the classes pp::Module and pp:Instance, which your app will need to implement.
On the HTML side, write a simple page with the EMBED element for the Native Client module. Then add the JavaScript event handlers for loadstart, progress, error, abort, load, loadend, and message and have the handlers write the event data to, e.g., the JavaScript console, so that it's possible to tell what went wrong if the Native Client module didn't load. The load_progress example shows how to do this.
Next, create the manifest file (.nmf). From pepper_18 and onwards you can use the generate_nmf.py script found in the tools/ directory for this. If you want to write it from scratch, the examples provide examples both for using newlib and glibc (the two Standard C librares currently supported). See hello_world_newlib/ and hello_world_glibc/, respectively.
If you haven't used a gcc-family compiler before, it is also a good idea to look at the Makefile for some of the examples to see what compiler and linker flags to use. Compiling both for 32-bit and 64-bit right from the beginning is recommended.
Easiest way is to follow the quick start doc at https://developers.google.com/native-client/pepper18/quick-start, in particular steps 5-7 of the tutorial ( https://developers.google.com/native-client/pepper18/devguide/tutorial ) which seems to be what you are asking about.

Application settings methods? c++

I am thinking about adding configurable settings to an application, and I think the easiest ways are an external file or win registry (its a win only app).
Which way would be better?
I was wondering, an user with not enough permissions may not be able to create/write the config file. And in the case of the registry, would todays antivirus allow me to add/edit/remove keys? Or they only monitor certain keys?
Also, if someone knows a class/lib to manage config settings (in pure win32) in vc++ please post it.
As far as I know:
an user with not enough permissions may not be able to create/write the config file
You should be able to make files inside user's "home directory" or "application data" directory, regardless of permissions. Normally those directories should be writeable.
would todays antivirus allow me to add/edit/remove keys?
Haven't ever seen my antivirus interfere with registry manipulation. You probably will be fine as long as you aren't doing anything suspicious in registry.
Which way would be better?
It is matter of taste. I think that text file is better - allows easier migration of settings. Just don't leave junk behind after uninstall.
Also, if someone knows a class/lib to manage config settings in vc++
QSettings in Qt 4. But using entire Qt for just saving settings is definitely an overkill. You could also check configuration languages like JSON, use lua for settings (less overkill than using Qt 4) or get any XML library. Also, working with registry directly or writing configuration files using iostreams or stdio shouldn't be hard. And you can always write your own configuration library - if you feel like it.
Is "Windows-only" a restriction or a restriction-relief? If you don't mind being cross-platform then I suggest you give boost::program_options a go. The library supports program options through commandline, through evironment-variables and through INI files. Boost's program_options also integrates and glues the various parsers very nicely with variables_map, which you can view as a map between options and their value.
For simple stuff, you might as well just use the registry. However, there are many benefits to a config file... you can save/load several different configs for different uses of your app, it's easier to share or migrate settings between users or machines, etc.
If you end up going the file route, I would recommend Boost's Property Tree library:
http://www.boost.org/doc/libs/1_41_0/doc/html/property_tree.html
It has a pretty nice syntax:
boost::property_tree::ptree properties;
std::string name = properties.get<std::string>("blah.name");
int score = properties.get<int>("blah.score");
properties.put("blah.name", "Inverse");
properties.put("blah.score", 1000);
It also supports reading and writing to various formats, like xml and others.
I think the new default thing is to write a configuration file in the user's "AppData" folder under the user's folder which should be safe to write/read from.
We're using a simple XML formatted file to store settings; but you could use a INI file type formatting.
If you save your configuration file in the Application Data directory SHGetFolderPath() with CSIDL_COMMON_APPDATA all users will be able to see the configuration. If you use CSIDL_LOCAL_APPDATA then only the one user will be able to see the configuration. The registry is not necessarily the place to save all configuration data.

C++ vim IDE. Things you'd need from it

I was going to create the C++ IDE Vim extendable plugin. It is not a problem to make one which will satisfy my own needs.
This plugin was going to work with workspaces, projects and its dependencies.
This is for unix like system with gcc as c++ compiler.
So my question is what is the most important things you'd need from an IDE? Please take in account that this is Vim, where almost all, almost, is possible.
Several questions:
How often do you manage different workspaces with projects inside them and their relationships between them? What is the most annoying things in this process.
Is is necessary to recreate "project" from the Makefile?
Thanks.
Reason to create this plugin:
With a bunch of plugins and self written ones we can simulate most of things. It is ok when we work on a one big "infinitive" project.
Good when we already have a makefile or jam file. Bad when we have to create our owns, mostly by copy and paste existing.
All ctags and cscope related things have to know about list of a real project files. And we create such ones. This <project#get_list_of_files()> and many similar could be a good project api function to cooperate with an existing and the future plugins.
Cooperation with an existing makefiles can help to find out the list of the real project files and the executable name.
With plugin system inside the plugin there can be different project templates.
Above are some reasons why I will start the job. I'd like to hear your one.
There are multiple problems. Most of them are already solved by independent and generic plugins.
Regarding the definition of what is a project.
Given a set of files in a same directory, each file can be the unique file of a project -- I always have a tests/ directory where I host pet projects, or where I test the behaviour of the compiler. On the opposite, the files from a set of directories can be part of a same and very big project.
In the end, what really defines a project is a (leaf) "makefile" -- And why restrict ourselves to makefiles, what about scons, autotools, ant, (b)jam, aap? And BTW, Sun-Makefiles or GNU-Makefiles ?
Moreover, I don't see any point in having vim know the exact files in the current project. And even so, the well known project.vim plugin already does the job. Personally I use a local_vimrc plugin (I'm maintaining one, and I've seen two others on SF). With this plugin, I just have to drop a _vimrc_local.vim file in a directory, and what is defined in it (:mappings, :functions, variables, :commands, :settings, ...) will apply to each file under the directory -- I work on a big project having a dozen of subcomponents, each component live in its own directory, has its own makefile (not even named Makefile, nor with a name of the directory)
Regarding C++ code understanding
Every time we want to do something complex (refactorings like rename-function, rename-variable, generate-switch-from-current-variable-which-is-an-enum, ...), we need vim to have an understanding of C++. Most of the existing plugins rely on ctags. Unfortunately, ctags comprehension of C++ is quite limited -- I have already written a few advanced things, but I'm often stopped by the poor information provided by ctags. cscope is no better. Eventually, I think we will have to integrate an advanced tool like elsa/pork/ionk/deshydrata/....
NB: That's where, now, I concentrate most of my efforts.
Regarding Doxygen
I don't known how difficult it is to jump to the doxygen definition associated to a current token. The first difficulty is to understand what the cursor is on (I guess omnicppcomplete has already done a lot of work in this direction). The second difficulty will be to understand how doxygen generate the page name for each symbol from the code.
Opening vim at the right line of code from a doxygen page should be simple with a greasemonkey plugin.
Regarding the debugger
There is the pyclewn project for those that run vim under linux, and with gdb as debugger. Unfortunately, it does not support other debuggers like dbx.
Responses to other requirements:
When I run or debug my compiled program, I'd like the option of having a dialog pop up which asks me for the command line parameters. It should remember the last 20 or so parameters I used for the project. I do not want to have to edit the project properties for this.
My BuildToolsWrapper plugin has a g:BTW_run_parameters option (easily overridden with project/local_vimrc solutions). Adding a mapping to ask the arguments to use is really simple. (see :h inputdialog())
work with source control system
There already exist several plugins addressing this issue. This has nothing to do with C++, and it must not be addressed by a C++ suite.
debugger
source code navigation tools (now I am using http://www.vim.org/scripts/script.php?script_id=1638 plugin and ctags)
compile lib/project/one source file from ide
navigation by files in project
work with source control system
easy acces to file changes history
rename file/variable/method functions
easy access to c++ help
easy change project settings (Makefiles, jam, etc)
fast autocomplette for paths/variables/methods/parameters
smart identation for new scopes (also it will be good thing if developer will have posibility to setup identation rules)
highlighting incorrect by code convenstion identation (tabs instead spaces, spaces after ";", spaces near "(" or ")", etc)
reformating selected block by convenstion
Things I'd like in an IDE that the ones I use don't provide:
When I run or debug my compiled program, I'd like the option of having a dialog pop up which asks me for the command line parameters. It should remember the last 20 or so parameters I used for the project. I do not want to have to edit the project properties for this.
A "Tools" menu that is configurable on a per-project basis
Ability to rejig the keyboard mappings for every possible command.
Ability to produce lists of project configurations in text form
Intelligent floating (not docked) windows for debugger etc. that pop up only when I need them, stay on top and then disappear when no longer needed.
Built-in code metrics analysis so I get a list of the most complex functions in the project and can click on them to jump to the code
Built-in support for Doxygen or similar so I can click in a Doxygen document and go directly to code. Sjould also reverse navigate from code to Doxygen.
No doubt someone will now say Eclipse can do this or that, but it's too slow and bloated for me.
Adding to Neil's answer:
integration with gdb as in emacs. I know of clewn, but I don't like that I have to restart vim to restart the debugger. With clewn, vim is integrated into the debugger, but not the other way around.
Not sure if you are developing on Windows, but if you are I suggest you check out Viemu. It is a pretty good VIM extension for Visual Studio. I really like Visual Studio as an IDE (although I still think VC6 is hard to beat), so a Vim extension for VS was perfect for me. Features that I would prefer worked better in a Vim IDE are:
The Macro Recording is a bit error prone, especially with indentation. I find I can easily and often record macros in Vim while I am editing code (eg. taking an enum defn from a header and cranking out a corresponding switch statement), but found that Viemu is a bit flakey in that deptartment.
The VIM code completion picks up words in the current buffer where Viemu hooks into the VS code completion stuff. This means if I have just created a method name and I want to ctrl ] to auto complete, Vim will pick it up, but Viemu won't.
For me, it's just down to the necessities
nice integration with ctags, so you can do jump to definition
intelligent completion, that also give you the function prototype
easy way to switch between code and headers
interactive debugging with breaakpoints, but maybe
maybe folding
extra bonus points for refactoring tools like rename or extract method
I'd say stay away from defining projects - just treat the entire file branch as part of the "project" and let users have a settings file to override that default
99% of the difference in speed I see between IDE and vim users is code lookup and navigation. You need to be able to grep your source tree for a phrase (or intelligently look for the right symbol using ctags), show all the hits, and switch to that file in like two or three keystrokes.
All the other crap like repository navigation or interactive debugging is nice, but there are other ways to solve those problems. I'd say drop the interactive debugging even. Just focus on what makes IDEs good editors - have a "big picture" view of your project, instead of single file.
In fact, are there any plugins for vim that already achieve this?