I find #include "../app/thing.h" very ugly and I would like to be able to import from the main root of my project, like this:
#include <project/app/submodule/thing.h>
(I know <> is generally used for external but I find it very cleaner)
How can I do that, from anywhere in my project?
You simply need to ensure that your build process sets an option to specify the starting point of the search.
For example, if your header is in:
/work/username/src/project/app/submodule/thing.h
then you need to include (assuming a POSIX-compliant compiler; AFAICR, even MSVC uses /I as the analogue of -I):
-I/work/username/src
as one of the compiler options. You can use that path from anywhere in your project since it is absolute. You just need a defined way for your build system to know what the setting should be, so that when it is moved to /home/someone/src/, you have only one setting to change.
See this answer for a more complete explanation about how the differences between the two formats work. Honestly, though, I think you might want to consider restructuring your folder hierarchy if you need to jump up a folder then jump into another folder to get something. Generally speaking, it's pretty common practice to keep all files local to your program local to each other in the folder structure (i.e. in the same folder), and all files that aren't local, but may be needed (such as header files for libraries used) in a sub-folder within the main program folder, or to include them at compile time.
It is important to note that in the answer I linked above, it explains that "<>" includes are IMPLEMENTATION DEPENDENT, so we'd really need to know what compiler you're using to tell you if you could or couldn't do that.
You can simply use the include directories option of your current compiler (-I usually) to achieve this.
Also note using the "" double quotes will just add to fallback for the compiler standard headers. Files included using the <>, are only guaranteed to search files from the compiler standard headers.
Related
I use a code with different libraries, which use names like defines.h. This does not only cause conflicts for identical filenames, but also creates confusion. From which library is the defines.h include?
Including as #include <library/defines.h> would be a clean solution, but then the include path would need to be the parent directory of the library, which is rather unclean again.
Is there some way to alias the include path, so that -I/path/to/library makes the headers available under library/headername.h?
Is there some way to alias the include path, so that -I/path/to/library makes the headers available under library/headername.h?
There seems to be no need to in this case. You can simply use -I/path/to which makes /path/to/library/headername.h available under library/headername.h.
That said, while there is no such compilation option (that I know of), you can create such "aliases" to file paths in most file systems. These aliases are called symbolic links. In this case, you could make a link /path/to/library/mylibrary that points to . which would make /path/to/library/headername.h available under mylibrary/headername.h assuming you've used -I/path/to/library.
At least on unixy systems, when you compile and install a library, headers are installed for example to
/usr/lib/libraryname/*.h
Or maybe something like
/opt/libraryname-1.2/include/libraryname/*.h
And then if necesssry (not installing to compiler's default include search path), right dir is added with compiler option, for gcc for example option
-I/opt/libraryname-1.2/include
Then just always do this in source code, trusting build system to have included the right search paths:
#include <libraryname/includefile.h>
In the following files:
app/main.cpp
app/config.hpp
app/show.hpp
app/file.hpp
lib/append.hpp
lib/clear.hpp
lib/reopen.hpp
lib/crypt.hpp
I have a problem. Imagine a few of my files use lib/crypt.hpp. For example in app/file.hpp I should write:
#include "../lib/crypt.hpp"
If I take this file to lib folder it does not work anymore. So I need a something like:
#include "LIB/crypt.hpp"
So, this LIB/ has meaning of (empty) in lib directory while it has meaning of "../lib/" in app directory.
Then I will have no worry about moving file.hpp from app to lib. I just need to fix the callers of it. But not what it calls.
Similar to concept of web programming frameworks. Is it possible in C/C++?
According to what you wrote you're searching for a way to move your sources around without worrying for hard-coded paths to your headers.
You didn't specify the compiler you're using so I'm not focusing on a specific one, anyway most C++ compilers have an option to specify one or more header search paths (on gcc you would just use something like -Ilib_parent_dir).
Once you've included your lib's parent path to the search list, you can move your sources around (as long as you don't move lib's headers) and have them include the right headers with something like #include <lib/crypt.hpp> (and keep include paths priority in mind)
This should be a cleaner and simpler way to achieve what you asked rather than using a macro.
Is there an automated way to take a large amount of C++ header files and combine them in a single one?
This operation must, of course, concatenate the files in the right order so that no types, etc. are defined before they are used in upcoming classes and functions.
Basically, I'm looking for something that allows me to distribute my library in two files (libfoo.h, libfoo.a), instead of the current bunch of include files + the binary library.
As your comment says:
.. I want to make it easier for library users, so they can just do one single #include and have it all.
Then you could just spend some time, including all your headers in a "wrapper" header, in the right order. 50 headers are not that much. Just do something like:
// libfoo.h
#include "header1.h"
#include "header2.h"
// ..
#include "headerN.h"
This will not take that much time, if you do this manually.
Also, adding new headers later - a matter of seconds, to add them in this "wrapper header".
In my opinion, this is the most simple, clean and working solution.
A little bit late, but here it is. I just recently stumbled into this same problem myself and coded this solution: https://github.com/rpvelloso/oneheader
How does it works?
Your project's folder is scanned for C/C++ headers and a list of headers found is created;
For every header in the list it analyzes its #include directives and assemble a dependency graph in the following way:
If the included header is not located inside the project's folder then it is ignored (e.g., if it is a system header);
If the included header is located inside the project's folder then an edge is create in the dependency graph, linking the included header to the current header being analyzed;
The dependency graph is topologically sorted to determine the correct order to concatenate the headers into a single file. If a cycle is found in the graph, the process is interrupted (i.e., if it is not a DAG);
Limitations:
It currently only detects single line #include directives (e.g., #include );
It does not handles headers with the same name in different paths;
It only gives you a correct order to combine all the headers, you still need to concatenate them (maybe you want remove or modify some of them prior to merging).
Compiling:
g++ -Wall -ggdb -std=c++1y -lstdc++fs oneheader.cpp -o oneheader[.exe]
Usage:
./oneheader[.exe] project_folder/ > file_sequence.txt
(Adapting an answer to my dupe question:)
There are several other libraries which aim for a single-header form of distribution, but are developed using multiple files; and they too need such a mechanism. For some (most?) it is opaque and not part of the distributed code. Luckily, there is at least one exception: Lyra, a command-line argument parsing library; it uses a Python-based include file fuser/joiner script, which you can find here.
The script is not well-documented, but they way you use it is with 3 command-line arguments:
--src-include - The include file to convert, i.e. to merge its include directives into its body. In your case it's libfoo.h which includes the other files.
--dst-include - The output file to write - the result of the merging.
--src-include-dir - The directory relative to which include files are specified (i.e. an "include search path" of one directory; the script doesn't support the complex mechanism of multiple include paths and search priorities which the C++ compiler offers)
The script acts recursively, so if file1.h includes another file under the --src-include-dir, that should be merged in as well.
Now, I could nitpick at the code of that script, but - hey, it works and it's FOSS - distributed with the Boost license.
If your library is so big that you cannot build and maintain a single wrapping header file like Kiril suggested, this may mean that it is not architectured well enough.
So if your library is really huge (above a million lines of source code), you might consider automating that, with tools like
GCC make dependency generator preprocessor options like -M -MD -MF etc, with another hand made script sorting them
expensive commercial static analysis tools like coverity
customizing a compiler thru plugins or (for GCC 4.6) MELT extensions
But I don't understand why you want an automated way of doing this. If the library is of reasonable size, you should understand it and be able to write and maintain a wrapping header by hand. Automating that task will take you some efforts (probably weeks, not minutes) so is worthwhile only for very large libraries.
If you have a master include file that includes all others available, you could simply hack a C preprocessor re-implementation in Perl. Process only ""-style includes and recursively paste the contents of these files. Should be a twenty-liner.
If not, you have to write one up yourself or try at random. Automatic dependency tracking in C++ is hard. Like in "let's see if this template instantiation causes an implicit instantiation of the argument class" hard. The only automated way I see is to shuffle your include files into a random order, see if the whole bunch compiles, and re-shuffle them until it compiles. Which will take n! time, you might be better off writing that include file by hand.
While the first variant is easy enough to hack, I doubt the sensibility of this hack, because you want to distribute on a package level (source tarball, deb package, Windows installer) instead of a file level.
You really need a build script to generate this as you work, and a preprocessor flag to disable use of the amalgamate (that could be for your uses).
To simplify this script/program, it helps to have your header structures and include hygiene in top form.
Your program/script will need to know your discovery paths (hint: minimise the count of search paths to one if possible).
Run the script or program (which you create) to replace include directives with header file contents.
Assuming your headers are all guarded as is typical, you can keep track of what files you have already physically included and perform no action if there is another request to include them. If a header is not found, leave it as-is (as an include directive) -- this is required for system/third party headers -- unless you use a separate header for external includes (which is not at all a bad idea).
It's good to have a build phase/translation that includes header alone and produces zero warnings or errors (warnings as errors).
Alternatively, you can create a special distribution repository so they never need to do more than pull from it occasionally.
What you want to do sounds "javascriptish" to me :-) . But if you insist, there is always "cat" (or the equivalent in Windows):
$ cat file1.h file2.h file3.h > my_big_file.h
Or if you are using gcc, create a file my_decent_lib_header.h with the following contents:
#include "file1.h"
#include "file2.h"
#include "file3.h"
and then use
$ gcc -C -E my_decent_lib_header.h -o my_big_file.h
and this way you even get file/line directives that will refer to the original files (although that can be disabled, if you wish).
As for how automatic is this for your file order, well, it is not at all; you have to decide the order yourself. In fact, I would be surprised to hear that a tool that orders header dependencies correctly in all cases for C/C++ can be built.
usually you don't want to include every bit of information from all your headers into the special header that enables the potential user to actually use your library. The non-trivial removal of type definitions, further includes or defines, that are not necessary for the user of your interface to know can not be automatedly done. As far as I know.
Short answer to your main question:
No.
My suggestions:
manually make a new header, that contains all relevant information (nothing more, nothing less) for the user of your library interface. Add nice documentation comments for each component it contains.
use forward declarations where possible, instead of full-fledged included definitions. Put the actual includes in your implementation files. The less include statements you have in your headers, the better.
don't build a deeply nested hierarchy of includes. This makes it extremely hard to keep an overview on the contents of every bit you include. The user of your library will look into the header to learn how to use it. And he will probably not be able to distinguish relevant code from irrelevant on the first sight. You want to maximize the ratio of relevant code per total code in the main header for your library.
EDIT
If you really do have a toolkit library, and the order of inclusion really does not matter, and you have a bunch of independent headers, that you want to enumerate just for convenience into a single header, then you can use a simple script. Like the following Python (untested):
import glob
with open("convenience_header.h", 'w') as f:
for header in glob.glob("*.h"):
f.write("#include \"%s\"\n" % header)
Why does tuple documentation say to use, for example:
#include "boost/tuple/tuple.hpp"
and not
#include <boost/tuple/tuple.hpp>
I know that it's not probable my code will have a file called "boost/tuple/tuple.hpp",
but using include <> states explicitly not to look in the curent directory.
So what is the reason?
Using <> does not mean "don't look in the current directory" - It means look in an implementation defined place and then look somewhere else, also implementation defined. Either, both or neither of these could be the current directory. This is one of the more useless bits of the C++ standard.
The historical meaning of <somefile> is to look in the system-standard places. With "somefile" it means look in the current directory, plus some other places.
Afaik the reason is to differentiate between headers that belong to an application and those which are from external libraries. I can't say why they have not used this convention. It is a only a convention and not a rule.
Perhaps someone should raise this issue with the Boost maintainers?
Use <...> for boost. This is not Your code. Unless your code is boost.
Use "...." for your header files, which you inevitably have in every C++ program. This is for the reader, not for the compiler.
From msdn:
Quoted form
This form instructs the preprocessor
to look for include files in the same
directory of the file that contains
the #include statement, and then in
the directories of any files that
include (#include) that file. The
preprocessor then searches along the
path specified by the /I compiler
option, then along paths specified by
the INCLUDE environment variable.
Angle-bracket form
This form instructs the preprocessor
to search for include files first
along the path specified by the /I
compiler option, then, when compiling
from the command line, along the path
specified by the INCLUDE environment
variable.
Are you asking what the difference between the two styles of inclusion is, or for Boost's rationale? Since others have spoken regarding the difference, I'll just add my take on the latter issue:
I don't believe either is more correct, in general. It depends on how your project is structured with respect to its dependencies. For example, in my projects I typically include the relevant bits of Boost, et cetera, in a subdirectory of the project and thus tend to prefer the #include "" form. If you want to pick up the Boost installation from a more global location, you'd prefer the #include <> form.
I am working on a large C++ project in Visual Studio 2008, and there are a lot of files with unnecessary #include directives. Sometimes the #includes are just artifacts and everything will compile fine with them removed, and in other cases classes could be forward declared and the #include could be moved to the .cpp file. Are there any good tools for detecting both of these cases?
While it won't reveal unneeded include files, Visual studio has a setting /showIncludes (right click on a .cpp file, Properties->C/C++->Advanced) that will output a tree of all included files at compile time. This can help in identifying files that shouldn't need to be included.
You can also take a look at the pimpl idiom to let you get away with fewer header file dependencies to make it easier to see the cruft that you can remove.
PC Lint works quite well for this, and it finds all sorts of other goofy problems for you too. It has command line options that can be used to create External Tools in Visual Studio, but I've found that the Visual Lint addin is easier to work with. Even the free version of Visual Lint helps. But give PC-Lint a shot. Configuring it so it doesn't give you too many warnings takes a bit of time, but you'll be amazed at what it turns up.
There's a new Clang-based tool, include-what-you-use, that aims to do this.
!!DISCLAIMER!! I work on a commercial static analysis tool (not PC Lint). !!DISCLAIMER!!
There are several issues with a simple non parsing approach:
1) Overload Sets:
It's possible that an overloaded function has declarations that come from different files. It might be that removing one header file results in a different overload being chosen rather than a compile error! The result will be a silent change in semantics that may be very difficult to track down afterwards.
2) Template specializations:
Similar to the overload example, if you have partial or explicit specializations for a template you want them all to be visible when the template is used. It might be that specializations for the primary template are in different header files. Removing the header with the specialization will not cause a compile error, but may result in undefined behaviour if that specialization would have been selected. (See: Visibility of template specialization of C++ function)
As pointed out by 'msalters', performing a full analysis of the code also allows for analysis of class usage. By checking how a class is used though a specific path of files, it is possible that the definition of the class (and therefore all of its dependnecies) can be removed completely or at least moved to a level closer to the main source in the include tree.
I don't know of any such tools, and I have thought about writing one in the past, but it turns out that this is a difficult problem to solve.
Say your source file includes a.h and b.h; a.h contains #define USE_FEATURE_X and b.h uses #ifdef USE_FEATURE_X. If #include "a.h" is commented out, your file may still compile, but may not do what you expect. Detecting this programatically is non-trivial.
Whatever tool does this would need to know your build environment as well. If a.h looks like:
#if defined( WINNT )
#define USE_FEATURE_X
#endif
Then USE_FEATURE_X is only defined if WINNT is defined, so the tool would need to know what directives are generated by the compiler itself as well as which ones are specified in the compile command rather than in a header file.
Like Timmermans, I'm not familiar with any tools for this. But I have known programmers who wrote a Perl (or Python) script to try commenting out each include line one at a time and then compile each file.
It appears that now Eric Raymond has a tool for this.
Google's cpplint.py has an "include what you use" rule (among many others), but as far as I can tell, no "include only what you use." Even so, it can be useful.
If you're interested in this topic in general, you might want to check out Lakos' Large Scale C++ Software Design. It's a bit dated, but goes into lots of "physical design" issues like finding the absolute minimum of headers that need to be included. I haven't really seen this sort of thing discussed anywhere else.
Give Include Manager a try. It integrates easily in Visual Studio and visualizes your include paths which helps you to find unnecessary stuff.
Internally it uses Graphviz but there are many more cool features. And although it is a commercial product it has a very low price.
You can build an include graph using C/C++ Include File Dependencies Watcher, and find unneeded includes visually.
If your header files generally start with
#ifndef __SOMEHEADER_H__
#define __SOMEHEADER_H__
// header contents
#endif
(as opposed to using #pragma once) you could change that to:
#ifndef __SOMEHEADER_H__
#define __SOMEHEADER_H__
// header contents
#else
#pragma message("Someheader.h superfluously included")
#endif
And since the compiler outputs the name of the cpp file being compiled, that would let you know at least which cpp file is causing the header to be brought in multiple times.
PC-Lint can indeed do this. One easy way to do this is to configure it to detect just unused include files and ignore all other issues. This is pretty straightforward - to enable just message 766 ("Header file not used in module"), just include the options -w0 +e766 on the command line.
The same approach can also be used with related messages such as 964 ("Header file not directly used in module") and 966 ("Indirectly included header file not used in module").
FWIW I wrote about this in more detail in a blog post last week at http://www.riverblade.co.uk/blog.php?archive=2008_09_01_archive.xml#3575027665614976318.
Adding one or both of the following #defines
will exclude often unnecessary header files and
may substantially improve
compile times especially if the code that is not using Windows API functions.
#define WIN32_LEAN_AND_MEAN
#define VC_EXTRALEAN
See http://support.microsoft.com/kb/166474
If you are looking to remove unnecessary #include files in order to decrease build times, your time and money might be better spent parallelizing your build process using cl.exe /MP, make -j, Xoreax IncrediBuild, distcc/icecream, etc.
Of course, if you already have a parallel build process and you're still trying to speed it up, then by all means clean up your #include directives and remove those unnecessary dependencies.
Start with each include file, and ensure that each include file only includes what is necessary to compile itself. Any include files that are then missing for the C++ files, can be added to the C++ files themselves.
For each include and source file, comment out each include file one at a time and see if it compiles.
It is also a good idea to sort the include files alphabetically, and where this is not possible, add a comment.
If you aren't already, using a precompiled header to include everything that you're not going to change (platform headers, external SDK headers, or static already completed pieces of your project) will make a huge difference in build times.
http://msdn.microsoft.com/en-us/library/szfdksca(VS.71).aspx
Also, although it may be too late for your project, organizing your project into sections and not lumping all local headers to one big main header is a good practice, although it takes a little extra work.
If you would work with Eclipse CDT you could try out http://includator.com to optimize your include structure. However, Includator might not know enough about VC++'s predefined includes and setting up CDT to use VC++ with correct includes is not built into CDT yet.
The latest Jetbrains IDE, CLion, automatically shows (in gray) the includes that are not used in the current file.
It is also possible to have the list of all the unused includes (and also functions, methods, etc...) from the IDE.
Some of the existing answers state that it's hard. That's indeed true, because you need a full compiler to detect the cases in which a forward declaration would be appropriate. You cant parse C++ without knowing what the symbols mean; the grammar is simply too ambiguous for that. You must know whether a certain name names a class (could be forward-declared) or a variable (can't). Also, you need to be namespace-aware.
Maybe a little late, but I once found a WebKit perl script that did just what you wanted. It'll need some adapting I believe (I'm not well versed in perl), but it should do the trick:
http://trac.webkit.org/browser/branches/old/safari-3-2-branch/WebKitTools/Scripts/find-extra-includes
(this is an old branch because trunk doesn't have the file anymore)
If there's a particular header that you think isn't needed anymore (say
string.h), you can comment out that include then put this below all the
includes:
#ifdef _STRING_H_
# error string.h is included indirectly
#endif
Of course your interface headers might use a different #define convention
to record their inclusion in CPP memory. Or no convention, in which case
this approach won't work.
Then rebuild. There are three possibilities:
It builds ok. string.h wasn't compile-critical, and the include for it
can be removed.
The #error trips. string.g was included indirectly somehow
You still don't know if string.h is required. If it is required, you
should directly #include it (see below).
You get some other compilation error. string.h was needed and isn't being
included indirectly, so the include was correct to begin with.
Note that depending on indirect inclusion when your .h or .c directly uses
another .h is almost certainly a bug: you are in effect promising that your
code will only require that header as long as some other header you're using
requires it, which probably isn't what you meant.
The caveats mentioned in other answers about headers that modify behavior
rather that declaring things which cause build failures apply here as well.