My Problem
I read somewhere that to add include paths to g++ you need to use the -I option:
g++ -I /some/directory and_then_my_files.cpp
However, I'm not sure if this is actually what I need. It's currently not working for me, and I couldn't find anything else close to what I have.
My Setup
I've got a directory with all my current project code, and in it a subdirectory classes, that contains various .h and .cpp files containing classes that may or may not be used when compiling my main files.
Since g++ ./classes/*.cpp main.cpp takes a long time (large number of files in classes directory), I'm looking for an alternative that only compiles and links the files that are included in the main file.
Main file:
#include "classes/a.h"
#include "classes/b.h"
// ... my code
And as you can imagine, g++ complains about undefined references to classes A and B, unless I add ./classes/*.cpp to the build command.
What I want to achieve
So -I and -L did not work, and adding the whole directory to the build command results in a ridiculously long build time - I'm talking 3-5 minutes, which really slows down my development speed.
Is there any way to only build/link the included classes from my classes directory, such as only classes A and B from the example I gave above?
Small Recap of what I've already tried
g++ -I ./classes main.cpp -o main
g++ -L ./classes main.cpp -o main (probably stupid but I tried it anyway)
g++ ./classes/*.cpp main.cpp -o main (what I currently have to resort to)
Thanks in advance :)
A temporary workaround
export CPLUS_INCLUDE_PATH=/usr/local/include
Related
I've just inherited some C++ code that was written poorly with one cpp file which contained the main and a bunch of other functions. There are also .h files that contain classes and their function definitions.
Until now the program was compiled using the command g++ main.cpp. Now that I've separated the classes to .h and .cpp files do I need to use a makefile or can I still use the g++ main.cpp command?
list all the other cpp files after main.cpp.
ie
g++ main.cpp other.cpp etc.cpp
and so on.
Or you can compile them all individually. You then link all the resulting ".o" files together.
To compile separately without linking you need to add -c option:
g++ -c myclass.cpp
g++ -c main.cpp
g++ myclass.o main.o
./a.out
Now that I've separated the classes to .h and .cpp files do I need to use a makefile or can I still use the "g++ main.cpp" command?
Compiling several files at once is a poor choice if you are going to put that into the Makefile.
Normally in a Makefile (for GNU/Make), it should suffice to write that:
# "all" is the name of the default target, running "make" without params would use it
all: executable1
# for C++, replace CC (c compiler) with CXX (c++ compiler) which is used as default linker
CC=$(CXX)
# tell which files should be used, .cpp -> .o make would do automatically
executable1: file1.o file2.o
That way make would be properly recompiling only what needs to be recompiled. One can also add few tweaks to generate the header file dependencies - so that make would also properly rebuild what's need to be rebuilt due to the header file changes.
.h files will nothing to do with compiling ... you only care about cpp files... so type g++ filename1.cpp filename2.cpp main.cpp -o myprogram
means you are compiling each cpp files and then linked them together into myprgram.
then run your program ./myprogram
I know this question has been asked years ago but still wanted to share how I usually compile multiple c++ files.
Let's say you have 5 cpp files, all you have to do is use the * instead of typing each cpp files name E.g g++ -c *.cpp -o myprogram.
This will generate "myprogram"
run the program ./myprogram
that's all!!
The reason I'm using * is that what if you have 30 cpp files would you type all of them? or just use the * sign and save time :)
p.s Use this method only if you don't care about makefile.
You can still use g++ directly if you want:
g++ f1.cpp f2.cpp main.cpp
where f1.cpp and f2.cpp are the files with the functions in them. For details of how to use make to do the build, see the excellent GNU make documentation.
As rebenvp said I used:
g++ *.cpp -o output
And then do this for output:
./output
But a better solution is to use make file. Read here to know more about make files.
Also make sure that you have added the required .h files in the .cpp files.
You can use several g++ commands and then link, but the easiest is to use a traditional Makefile or some other build system: like Scons (which are often easier to set up than Makefiles).
If you want to use #include <myheader.hpp> inside your cpp files you can use:
g++ *.cpp -I. -o out
I used to use a custom Makefile that compiled all the files in current directory, but I had to copy it in every directory I needed it, everytime.
So I created my own tool - Universal Compiler which made the process much easier when compile many files.
You can do that using a single command assuming all the needed .cpp and .h files are in the same folder.
g++ *.cpp *.h -Wall && ./a.out
It will compile and execute at the same time.
when using compiler in the command line, you should take of the following:
you need not compile a header file, since header file gets substituted in the script where include directive is used.
you will require to compile and link the implementation and the script file.
for example let cow.h be header file and cow.cpp be implementation file and cow.cc(c++ files can have extension .cpp, .cc, .cxx, .C, .CPP, .cp) be script file.
Since gcc compiler notation for c++ file is g++, we can compile and link the files using
$g++ -g -Wall cow.cpp cow.cc -o cow.out
options '-g' and '-Wall' are for debugging info and getting warning for errors. Here cow.out is the name of the executable binary file that we can execute to run the program. it is always good to name your executable file otherwise name will be automatically given which might be confusing at times.
you can also do the same by using makefiles, makefiles will detect, compile and link automatically the specified files.
There are great resources for compilation using command line
enter link description here
~/In_ProjectDirectory $ g++ coordin_main.cpp coordin_func.cpp coordin.h
~/In_ProjectDirectory $ ./a.out
... Worked!!
Using Linux Mint with Geany IDE
When I saved each file to the same directory, one file was not saved correctly within the directory; the coordin.h file. So, rechecked and it was saved there as coordin.h, and not incorrectly as -> coordin.h.gch. The little stuff.
Arg!!
Good Day Everyone,
N.B - This problem has been solved - I have provided my own solution in the answer section however the solution provided by Jonathan is much shorter. Nevertheless, this was the following question I originally posted:
I am basically trying to compile a serial library (for UART communication) on Linux however I am not really sure how to correctly compile (I have mentioned what I have done so far below), any suggestions would be highly valuable. I am using the serialib library - which is composed of 2 main files (serialib.h and serialib.cpp) , you may directly view the source code of these files here (scroll all the way to the bottom and view the files in new tabs): http://serialib.free.fr/html/classserialib.html
I transferred these files (serialib.h and serialib.cpp) to my BeagleBone Black micro-controller which is running Debian (Wheezy) , g++/gcc (Debian 4.6.3-14) 4.6.3. I wrote my own program (uart.cpp is my file name) to access the functions provided by this library, this is what I wrote:
#include <iostream>
#include "serialib.h"
#ifdef __linux__
#define DEVICE_PORT "/dev/ttyO1"
#endif
int main()
{
serialib LS;
return 0;
}
So as you can see I am trying to access the 'seriallib' class. serialib.h, serialib.cpp and uart.cpp are all in the home directory. I also manually added the iostream library in serialib.cpp as I did not see it being declared in the original source code.
Now I am really unsure of how to compile such external libraries but so far I tried the following steps:
g++ -c -Wall -Werror -fPIC serialib.c to convert to PIC which gives the following error:
distcc[3142] (dcc_parse_hosts) Warning: /home/debian/.distcc/zeroconf/hosts contained no hosts; can't distribute work
distcc[3142] (dcc_zeroconf_add_hosts) CRITICAL! failed to parse host file.
distcc[3142] (dcc_build_somewhere) Warning: failed to distribute, running locally instead
g++ serialib.cpp -L /home/debian/serialib.h which gives the following error:
/usr/lib/gcc/arm-linux-gnueabihf/4.6/../../../arm-linux-gnueabihf/crt1.o: In function _start':
(.text+0x30): undefined reference tomain'
collect2: ld returned 1 exit status
distcc[3210] ERROR: compile serialib.cpp on localhost failed
As of now I am still finding out how to compile this and if I manage to work this out then I'll post my solution here too. Once again any suggestion will be highly valuable. Thank you all :) .
g++ -c -Wall -Werror -fPIC serialib.c to convert to PIC which gives the following error:
The "error" is not an error, it's a warning, telling you that your distcc setup is broken, but that it compiled locally.
That command doesn't "convert to PIC", it compiles the file serialib.c and produces a compiled object file, serialib.o
g++ serialib.cpp -L /home/debian/serialib.h
This is just nonsense. It tries to build a program from serialib.cpp and use the directory /home/debian/serialib.h (which isn't a directory!) to find libraries.
You don't need to "compile a library" you can just compile both the source files and link them together into a program. Either:
g++ -c serialib.cpp
g++ -c uart.cpp
g++ serialib.o uart.o -o uart
Or all in one command:
g++ serialib.cpp uart.cpp -o uart
You should read An Introduction to GCC to understand the commands, not just enter bogus commands without understanding them.
I have found a solution to this problem, hope this helps for all the future readers with similar problems. I have my own source code uart.cpp (Given in the question) which I want to compile, the external library is serialib that contains two main files (serialib.h and serialib.cpp), you will want to replace the following commands with respect to the files you have
Step 1: Compiling with position independent code
g++ -c -Wall -Werror -fpic serialib.cpp
Step 2: Creating a shared library
g++ -shared -o libserialib.so serialib.o , here the library is libserialib.so.
Step 3: Linking your source code with library
g++ -L /home/debian -lserialib uart.cpp -o uart
g++ -L /home/debian -Wall -o test uart.cpp -lserialib
You may save the library at a different path and you may have a different name of course. Suppose you have a library called libabc.so at the directory /home/user/myDir then the commands will be like:
g++ -L /home/user/myDir -labc your_code.cpp -o your_code
g++ -L /home/user/myDir -Wall -o test your_code.cpp -labc
test is out own program, lserialib is actually looking for libserialib.so and not serialib.o as gcc/g++ assumes all libraries start with lib and end with .so or .a and you can see the same goes for labc as it will look for libabc.so thus it is important to make sure your library name begins with lib and ends with .so or .a
Step 4: Making library available at run time
Here we provide the path where the library is actually stored, I saved it in the directory /home/debian which is why my command looks like:
export LD_LIBRARY_PATH=/home/debian:$LD_LIBRARY_PATH
if your library is saved at /path/to/file then the command will look like:
export LD_LIBRARY_PATH=/path/to/file:$LD_LIBRARY_PATH
This is to help the loader find the shared library and to view this path: echo $LD_LIBRARY_PATH and to unset this: unset LD_LIBRARY_PATH
To execute the program type either ./test or ./uart and in case of any modification to the main source code (uart.cpp in this case) , simply repeat step 3. I found the following link very useful: http://www.cprogramming.com/tutorial/shared-libraries-linux-gcc.html . Thank you to all of you who took time to read this question and especially those who gave me suggestions. If anyone has more or better solutions, feel free to post them here to assist future readers :).
Im a beginner in C++ and working with unix. So here is my question.
I`ve written few lines in the main-function, and i needed a function, that is defined in the c_lib - library.
main.cpp:
#include <iostream>
#include "c_lib.cpp"
int main()
{
return 0;
}
i want to execute it on the terminal, so i wrote
g++ -c c_lib.cpp
g++ -c main.cpp
g++ -o run c_lib.o main.o
Until here, there is no error report.
Then
./run
I get the error
error: ./run: No such file or directory
What's wrong?
Including a .cpp is not usually done, usually only headers are included. Headers usually contain the declarations that define the interface to the code in the other .cpp
Can you show us the source of c_lib? That may help.
As the source of c_lib is #included, there is no need to compile it seperately. In fact this can/will cause errors (multiple definitions being the first to come to mind). You should only need to do:
g++ -o run main.cpp
to compile your code in this case.
(When using a header (.h), you will need to compile the implementation (.cpp) seperately)
Compile with warnings turned on:
g++ -Wall -Wextra -o run main.cpp
and you will get more output if there are problems with your code.
Is the run file being output by gcc? You can test by calling ls in the terminal (or ls run to only show the executable if it is present).
If the executable is present, it could be that it isn't marked as runnable. I'll go into that if it is a problem as it is outside the general scope of the site (though still related)
First of all you should not include source file into another source. You should create a header file and put declarations there (that allows main() to call functions from c_lib.cpp or use global variables if any)
When you run g++ you have to look into it's output, if operation succeed or not. In your case it failed so executable run was not created.
Usually you do not call compiler manually but write a makefile and let make utility to call g++.
I already asked how to call a C++ constructor from a C file in How to call a C++ constructor from a C-File. Now when I successfully apply these methods suggested there, I receive an error
fatal error: string: No such file or directory compilation terminated
this error message points to the line: #include <string> in a header of a .cpp file.
I already found out that <string> is used by c++/g++ and <string.h> by c/gcc. Well the problem got clearer, when I checked the console output and there I can see, the (.cpp) file with the error was called by the gcc, which actually expects the <string.h> but that's not my intention - I need to compile it with the g++.
Now my question is: Can I force Eclipse to use a specific compiler? Here, for example just g++ (I heared it is capable of C-code too.) - Or even better, is there a way to chose the compiler for each directory in the workspace ?
Thanks for your advises
Answer respecting the wish of being able to specify the compiler for every subfolder:
What you are searching is probably a makefile project. That allows you to specify the toolchain, being for example the preprocessor, compiler and linker. g++ is an example for such a toolchain, as much as clang++ would be.
You can generate such a project in eclipse, writing the makefiles by hand, or use some build environment, such as CMake, which I would recommend for better portable code.
Both solutions would allow you to specify the compiler, as well as the compile flags, for every single directory of your project, if you wished so.
Writing a makefile for your existing C/C++ project can be achieved by completing the following steps:
in the folder where your source file is, right click and create a new file. New > File
name it makefile and click Finish
The new makefile should pop up in the editor and can be filled like follows:
makefile:
all: executable_name
clean:
-rm main.o executable_name[.exe on windows] executable_name
executable_name: main.o
g++ -g -o executable_name main.o
main.o: main.cpp
g++ -c -g main.cpp
Change Project's Setting can force eclipse to compile using g++:
I've just inherited some C++ code that was written poorly with one cpp file which contained the main and a bunch of other functions. There are also .h files that contain classes and their function definitions.
Until now the program was compiled using the command g++ main.cpp. Now that I've separated the classes to .h and .cpp files do I need to use a makefile or can I still use the g++ main.cpp command?
list all the other cpp files after main.cpp.
ie
g++ main.cpp other.cpp etc.cpp
and so on.
Or you can compile them all individually. You then link all the resulting ".o" files together.
To compile separately without linking you need to add -c option:
g++ -c myclass.cpp
g++ -c main.cpp
g++ myclass.o main.o
./a.out
Now that I've separated the classes to .h and .cpp files do I need to use a makefile or can I still use the "g++ main.cpp" command?
Compiling several files at once is a poor choice if you are going to put that into the Makefile.
Normally in a Makefile (for GNU/Make), it should suffice to write that:
# "all" is the name of the default target, running "make" without params would use it
all: executable1
# for C++, replace CC (c compiler) with CXX (c++ compiler) which is used as default linker
CC=$(CXX)
# tell which files should be used, .cpp -> .o make would do automatically
executable1: file1.o file2.o
That way make would be properly recompiling only what needs to be recompiled. One can also add few tweaks to generate the header file dependencies - so that make would also properly rebuild what's need to be rebuilt due to the header file changes.
.h files will nothing to do with compiling ... you only care about cpp files... so type g++ filename1.cpp filename2.cpp main.cpp -o myprogram
means you are compiling each cpp files and then linked them together into myprgram.
then run your program ./myprogram
I know this question has been asked years ago but still wanted to share how I usually compile multiple c++ files.
Let's say you have 5 cpp files, all you have to do is use the * instead of typing each cpp files name E.g g++ -c *.cpp -o myprogram.
This will generate "myprogram"
run the program ./myprogram
that's all!!
The reason I'm using * is that what if you have 30 cpp files would you type all of them? or just use the * sign and save time :)
p.s Use this method only if you don't care about makefile.
You can still use g++ directly if you want:
g++ f1.cpp f2.cpp main.cpp
where f1.cpp and f2.cpp are the files with the functions in them. For details of how to use make to do the build, see the excellent GNU make documentation.
As rebenvp said I used:
g++ *.cpp -o output
And then do this for output:
./output
But a better solution is to use make file. Read here to know more about make files.
Also make sure that you have added the required .h files in the .cpp files.
You can use several g++ commands and then link, but the easiest is to use a traditional Makefile or some other build system: like Scons (which are often easier to set up than Makefiles).
If you want to use #include <myheader.hpp> inside your cpp files you can use:
g++ *.cpp -I. -o out
I used to use a custom Makefile that compiled all the files in current directory, but I had to copy it in every directory I needed it, everytime.
So I created my own tool - Universal Compiler which made the process much easier when compile many files.
You can do that using a single command assuming all the needed .cpp and .h files are in the same folder.
g++ *.cpp *.h -Wall && ./a.out
It will compile and execute at the same time.
when using compiler in the command line, you should take of the following:
you need not compile a header file, since header file gets substituted in the script where include directive is used.
you will require to compile and link the implementation and the script file.
for example let cow.h be header file and cow.cpp be implementation file and cow.cc(c++ files can have extension .cpp, .cc, .cxx, .C, .CPP, .cp) be script file.
Since gcc compiler notation for c++ file is g++, we can compile and link the files using
$g++ -g -Wall cow.cpp cow.cc -o cow.out
options '-g' and '-Wall' are for debugging info and getting warning for errors. Here cow.out is the name of the executable binary file that we can execute to run the program. it is always good to name your executable file otherwise name will be automatically given which might be confusing at times.
you can also do the same by using makefiles, makefiles will detect, compile and link automatically the specified files.
There are great resources for compilation using command line
enter link description here
~/In_ProjectDirectory $ g++ coordin_main.cpp coordin_func.cpp coordin.h
~/In_ProjectDirectory $ ./a.out
... Worked!!
Using Linux Mint with Geany IDE
When I saved each file to the same directory, one file was not saved correctly within the directory; the coordin.h file. So, rechecked and it was saved there as coordin.h, and not incorrectly as -> coordin.h.gch. The little stuff.
Arg!!