import file as variable in compilation(CPP) - c++

I have a CPP file which depends on having a vary large string being declared at the start of the file. I would like to be able to import this string from a text file, and include as a variable during compilation. Please could a shell script and relevant C/++ code be provided.

You can declare this string in a header file and include this file.

You can't do that without external help.
There're plenty of so-called "binary to header" scripts and programs out there. As an example, https://github.com/dparnell/bin2h (just a top hit from a search engine).
EDIT: Also, take a look at How to use bin2h?.

Related

When a file changes, I'd like to modify one or more different files

I've been scouring the web for hours looking for an approach to solving this problem, and I just can't find one. Hopefully someone can fast-track me. I'd like to cause the following behaviour:
When running ember s and a file of a certain extension is changed, I'd like to analyze the contents of that file and write to several other files in the same directory.
To give a specific example, let's assume I have a file called app/dashboard/dashboard.ember. dashboard.ember consists of 3 concatenated files: app/dashboard/controller.js, .../route.js, and .../template.hbs with a reasonable delimiter between the files. When dashboard.ember is saved, I'd like to call a function (inside an addon, I assume) that reads the file, splits it at the delimiter and writes the corresponding splitted files. ember-cli should then pick up the changed source (.js, .hbs, etc.) files that it knows how to handle, ignoring the .ember file.
I could write this as a standalone application, of course, but I feel like it should be integrated with the ember-cli build environment, but I can't figure out what concoction of hooks and tools I should use to achieve this.

Make variables defined in python readable by other languages

I have a python module that defines some paths when imported. I want those paths to be readable by scripts in c++ and shell.
One option would be to make a text file with those paths, and write a reader in python, c++ and shell, and then start all my scripts with the respective reader, but it's a solution I dislike. I would be constantly opening the text file, and it could give me issues if more than one script tries opening it at the same time.
Another solution would be to have the python file define the paths as environment variables instead. The usual way to do environment variables in python, os.environ, only lasts until I close python. Could anyone tell me how to do this?
(Defining these variables in my .bashrc would be quite the headache, because the module will also be used by other people, and the paths have to be changed from time to time.)
Any other way to solve this problem would also be appreciated.

Include static data/text file

I have a text file (>50k lines) of ascii numbers, with string identifiers, that can be thought of as a collection of data vectors. Based on user input, the application only needs one of these data vectors at runtime.
As far as I can see, I have 3 options for getting the information from this text file:
Keep it as a text file, extract the required vector at run-time. I believe the downside is that you can't have a relative path in the code, so the user would have to point to the file's correct location (?). Or alternatively, get the configure script to inject the absolute path as a macro.
Convert it to a static unsigned char using xxd (as explained here) and then include the resulting file. Downside is that a 5MB file turns into a 25MB include file. Am I correct in thinking that this 25MB is loaded into memory for the duration of the runtime?
Convert it to an object and link using objcopy as explained here. This seems to keep the file size about the same -- are there other trade-offs?
Is there a standard/recommended method for doing this? I can use C or C++ if that makes a difference.
Thanks.
(Running on linux with gcc)
I would go with number 1 and pass the filepath into the program as an argument. There's nothing wrong with doing that and it is simple and straight-forward.
You should have a look at the answers here:
Directory of running program
The top voted answer gives you a glue how to handle your data file. But instead of the home folder I would suggest to save it under /usr/share as explained in the link.
I'd preffer to use zlib (and both ways are possible:side file or include with compressed data).

FOO.tab.cpp file in folder FOO part of a larger project. Is there special significance of *.tab.cpp?

This might be difficult to answer. I am trying to understand some codebase and in one of the project folders named FOO there is a main.cpp file plus other .hpp and .cpp files. These filenames are made descriptive using underscores such as Hi_there_file.cpp etc.
There are two files Foo.tab.hpp and Foo.tab.cpp
Is *.tab.cpp an indication of something or just a poor try at making the file name descriptive?
Turns out, that file is generated by a perl script so they put a tab.cpp at the end. maybe even delete this question. Very very specific to what i'm working with

Is it possible to have identically named source files in one visual studio c++ project?

I'm working on a static library project for a c++ course I'm taking. The teacher insists that we define only one function per source file, grouping files/functions belonging to the same class in subdirectories for each class. This results in a structure like:
MyClass
\MyClass.cc (constructor)
\functionForMyClass.cc
\anotherFunctionForMyClass.cc
OtherClass
\OtherClass.cc (constructor)
Whether this is good practice or not is something I'd not like to discuss, since I'm simply obliged to organize my project in this manner.
I'm working in visual studio 2008, and somehow got strange link errors when using an identically named function (and thus filename) in two classes. This appears to be caused by the fact that visual studio puts all .obj files (one for each source file) in one intermediate directory, overwriting earlier generated object files when compiling identically named source files.
This could be solved by putting the object files in subdirectories based on the relative path of the input file. Visual studio allows one to configure the names of object files it generates and has macros to use in there, but there appears to be no macro for 'relative path of input file'.
So, is there some way to get this to work? If not, is using one project for each class the best work-around?
You are right, by default all object files are put into the same directory and their filenames are based on the source file name. The only solution I can think of is to change conflicting file's output file path in here:
Project Properties-C/C++-Output Files-Object File Name http://img37.imageshack.us/img37/3695/outputfile.png
PS. It sounds like the lecturer has a crappy (probably written by the lecturer himself) automatic code verifier that imposes this restriction. To get extra marks, offer to rewrite the parser so it works with normal/sane/non-weird projet layout.
Real answer:
Change
C/C++ => Output Files => Output File Name
to
$(IntDir)/%(RelativeDir)/
Every .obj file is going to be created in a sub folder so its not going to overwrite the previous on linking.
I can't think of any way to fudge the project settings to get VStudio to automatically split out the intermediate files into separate folders.
You have a few chances -
Build the class name into each file name. Most IDE's display just the file name in the tab view so if you do have several methods in different classes with the same name, its going to be difficult to tell them apart if the file name does not include the class name along with the method name. Which is really why I think your teachers advice is madness. I have not seen any programming style guide advocating that approach. Additionally it goes directly against the way various tools work - if you use Visual Studio to create a class, it creates one cpp file and one header, and automatically appends each new function to the single cpp file.
You could create a static library per class. When linking in static libs the obj files are all packaged up inside the .lib so conflicts are no longer a problem.
Switch comp-sci courses to one thats not being taught by a nut job. Seriously, this guy is completely out of touch with industry best practices and is trying to impose their own weird ideas on their students: Ideas that are going to have to be unlearnt the moment they leave the teaching environment.
You can also change output file name per file in its properties. Just make sure you use different names.
Can you use the class name in the filename to disambiguate? I'm thinking that you might have
MyClass
\MyClass.cc (constructor)
\function1_MyClass.cc
\function2_MyClass.cc
That would mean that every file would have a unique-enough name to defeat the problem. Is that an acceptable strategy?
You could probably arrange the properties of the project to put the object files into a folder which is below the folder of each source file. Once the project has this property, then every source file should inherit this property. (But if you've done experiments like Igor has suggested, then you may need to go through the properties as reset them back to the parent).
Having looked at the help files, I think you should go to project properties/C C++/Outpuf Files/Object File Name: and enter $(InputDir) (no trailing backslash). Every source file should then inherit this property and your .obj files should be separated.
You may need to do a Clean Solution before you make any changes.
Renaming the object files will work, but it's going to be a pain, and it will slow your compile/link cycle down. I've never figured out why, but it seems to confuse Visual Studio if the object files don't have the default names.
You could prefix the funciton name with the class name; e.g. myclass-ctor.cc, myclass-function1.cc etc.
You could have one .cc file per class which #includes the individual function files. In this case you'll need to prevent the #included files from being compiled seperately (either rename their extension or set Properties->Exclude From Build to 'Yes').
Out of curiosity, where does your teacher want you to put free functions e.g. local helper functions that might normally belong in an anonymous namespace?
If not, is using one project for each class the best work-around?
Not a good idea - apart from the fact that you won't end up with a single static library (without even more jiggery pokery), your link times are likely to increase and it will hide a
lot of pertinent info from the optimizer.
On another note; If the course is actually about C++ not OO programming, do what you need to pass but take your teacher's advice with a pinch of salt.
You don't have to put them in different translation units... why not put each function in a .h and include them all in one .cc per class? That will very likely give better output from the compiler.
I'd be asking why the teacher is insisting on this odd structure, too, the reasoning behind it should be explained. I know you didn't ask that of us, so that's all I'll say.
In Visual Studio 2010, I set
Properties -> C/C++ -> Output Files -> Output File Name
to
V:\%(Directory)$(PlatformName)_$(ConfigurationName)_%(Filename).obj
for OBJ files to end up next to the sources assuming the project lies on drive V (no idea whether there is a macro for it, yet).
By the way: $(InputDir) refers to the solution/project directory and will cause the same problem in another directory.