I am writing some OpenGL code, and my links to libraries in /usr/lib is getting quite unwieldly:
g++ Application.cpp -lglfw -lGL -lGLEW
I don't want to hunt around/can't remember the exact names of the libraries EVERY TIME i want to complile something, so in my project folder I have a file called linkingsNeeded.txt. That file contains that command and nothing else. Is there a way to save the list of linkings so I can just type
g++ Application.cpp
And not have to deal with manually linking? Say, in the #include section of the CPP file?
Learn to use some build automation tool such as GNU make or ninja.
You'll then edit your Makefile (with make); this could be inspirational and just build your program by typing make. Most source code editors (like GNU emacs) or IDEs can be easily configured to run make with a single keypress.
Of course you want to invoke GCC as g++ -Wall -Wextra -g since you want all warnings and debug info (for the GDB debugger).
Read also How to debug small programs and more about C++, perhaps even the n3337 quasi C++11 standard.
Related
environment A: centos7(same os) / gcc.7.3.1(higher gcc)
environment B: centos7(same os) / gcc.4.8.5(lower gcc)
I have built an C++ executable in environment A and run it in environment B.
I haven't had a problem so far, but could there be a problem with this approach?
Technically, building a static executable improves portability.
So compile your C++ files with g++ -O -Wall -Wextra -g and link the object files with g++ -static *.o
Alternatively, use dynamically only libc.so, not the C++ standard library. So link with g++ *.o -Bstatic your libraries -Bdynamic -lc
For details, read the documentation of GCC, of GNU binutils, perhaps of GNU bash, and the Program Library Howto and Drepper's paper How to write shared libraries
Notice that to run an executable (see elf(5) and execve(2) and other syscalls(2)....) you don't need a compiler.
You may want to use strace(1) and ldd(1) on machine B.
Don't forget to have many testcases.
Notice that GCC, Bash, Binutils, are free software. You are allowed to download and study their source code and improve it (there are licensing conditions when you redistribute an improved binary, read their GPL license)
You could have legal or licensing issues (e.g. if your C++ code uses Qt). You may need to consult a lawyer about them.
See also LinuxFromScratch.
What's a good way to find the necessary libraries needed to link against when making a toy executable to play around with another library?
I'll get the appropriate compile command from the compile_commands.json file (generated by CMake), but I still have to manually figure out which libraries I need the executable to link to.
For example: if I have a file called main.cpp:
#include <some_cool_library.hpp>
#include <iostream>
int main() {
some_cool_library::some_cool_type obj{"35"};
return 0;
}
I'll grab the appropriate compile command from the compile_commands.json file that was generated in the project that utilized some_cool_library.hpp (this is so I can pass the correct -I flag(s) to compiler without having to think at all).
Then I'll compile it (making the appropriate compile command modifications):
/usr/bin/clang++ -DBOOST_ALL_NO_LIB -DBOOST_ASIO_HAS_STD_CHRONO -DHAS_ZLIB -DWEBSOCKETPP_STRICT_MASKING -I<some-dir0> -I<some-dir1> -I<some-dir2> -isystem /usr/local/include -Wall -Wno-invalid-partial-specialization -O3 -DNDEBUG -pthread -std=gnu++17 -o prog /home/user/main.cpp && ./prog
Lastly I'll get some output that spits back a bunch of linker errors where I have to manually inspect each one and link the appropriate library. Is there a better way to find these libraries?
The standard way to learn how to use a library is to read that library's documentation.
In some cases, pkg-config can be used to get the necessary compiler and linker flags. This is not guaranteed to work, but there is a reasonable chance of it working if CMake seems to automagically handle the library as a dependency.
As we know, in the appliance when we use the command
make [file-name]
It automatically compiles with some flags:
-ggdb -O0 -std=c99 -Wall - Werror
I need to know in which directory the CS50 edited Makefile is located, because I want to configure my own Makefile for the entire system by which I can make any .cpp file.
When I compile c++ file with make it automatically compiles with g++ but I want to compile .cpp file with clang++ compiler, adding some essential flag such for -g for debugging -O0 for assembly code.
I'm asking how to create a Makefile for that specific reasons, if possible.
Make uses Makefiles in the current directory and Implicit-Rules. You can modify the behavior of implicit rules by changing the variables that those explicit rules use.
For example, to change the compiler for .cpp files, you could set your own CXX variable, either
in the environment (Make uses it):
CXX=clang++ make [file-name]
#OR
export CXX=clang++; make [file-name]
in a local Makefile:
CXX:=clang++
#The implicit rule, which you'll find in the link, takes care of the rest
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'm playing around with a toolchain that seems to wrap gcc (qcc), but also uses g++ for a few things. This caused a bit of confusion when I couldn't link libs I built with g++ using g(q)cc even though it was for the same architecture (due to missing lib errors). After a bit more research, I found that g++ is basically gcc with a few default flags and a slightly different interpretation mechanism for file extensions (there may be other differences I've glanced over). I'd like to know exactly which flags can be passed to gcc to amount to the equivalent g++ call. For instance:
g++ -g -c hello.cpp // I know at the very least that this links in stl
gcc -g -c -??? // I want the exact same result as I got with g++... what flags do I use?
The way the tool chain is set up makes it sort of difficult to simply replace the gcc calls with g++. It'd be much easier to know which flags I need to pass.
The differences between using gcc vs. g++ to compile C++ code is that (a) g++ compiles files with the .c, .h, and .i extensions as C++ instead of C, and that (b) it automatically links with the C++ standard library (-lstdc++). See the man page.
So assuming that you're not compiling .c, .h., or .i files as C++, all you need to do to make gcc act like g++ is add the -lstdc++ command line option to your linker flags. If you are compiling those other files as C++, you can add -x c++, but I'd advise you instead to rename them to use .cc or .ii files (.h can stay that way, if you're using precompiled headers).