I am trying to use a linear algebra package called hnfprof. I have done the installation with the given instructions and now its ready to use. Now I want to use some functions in hnfproj/src/lift/lift.c file. I want to create my own matrix examples and check outputs for each functions separately. I am not clear how to do this. (I know only basics of C language, creating .c files in a folder and running it in my Ubuntu terminal.)
I know that I should write a C file including this "#include <lift.c>" file name and creating a matrix in my file "main.c". I don't know how to include a file name in a different location. When I compile I can not use "gcc -o program main.c lift.c". My "main.c" file is in a different folder. I don't want to create any make file inside the package folder. So how I can just use the "lift.c" file inside my "main.c" file which is in a separate folder "Main" and create all executable make files inside "Main" folder?
If its difficult to give a answer, appreciate if you can suggest me some source to learn this. Thank you
No need to include lift.c directly in main.c, and you can call function in lift.c from main.
When it comes to compilation, you can use:
gcc -o program main.c file_location/lift.c
If you need other options, add them (most flags at the start; libraries at the end, after the source code). You can also compile each file to object code separately and then link the object files together:
gcc -c main.c
gcc -c file_location/lift.c
gcc -o program main.o lift.o
refer
Compiling multiple C files with gcc
I have a compiled C file, called Hello.o. in Hello.o:
I have a main function
and a function called int myfunc().
I wonder if I were to create a new file, hello2.c that contains a main function as well, and declare myfunc at the top of hello2.c,
will i be able to compile hello2.c and link hello.o to it using a gcc command?
Thanks all in advance.
If you want to just use myfunc() in hello2.c you can try linking the two objects files using gcc.Declare the function in a header file Hello.h and include it in hello2.c and generate Hello.o and hello2.c before linking them together by
$ gcc -o output Hello.o hello2.o
I think this should help you
How do I link object files in C? Fails with "Undefined symbols for architecture x86_64"
Object files are linked completely, or not at all. So this won't work.
GCC adds all the files specified in the command line as .o to the binary. Then the libraries (.a) are used to find needed symbols.
If there are duplicate symbols, an error is reported. (It doesn't know which main).
If a library contains more than one .o file, it can ignore the .O files which are not required. These may have duplicates with the binary.
I have three C files in total. One is a header [.h] file, two are source [.c] files.
The .h file is called encryption.h and the corresponding source file is encryption.c. The encryption.c has logic, but no main() function. My second c file is called main.c. There I have the main() function that calls methods from encryption.c.
I am compiling these files within terminal on Mac OSx. I am confused on how to compile this, I have tried the following:
gcc -c main.c
gcc -c encryption.c
gcc -c encryption.h
gcc main.o encryption.o encryption.g.gch -o encrypt
This doesn't seem to work though, it says I have a precompiled-header already. I tried finding the answer online, I know it has to be simple, but I haven't had much luck. What is the issue here?
Don't compile the header file. Header files are meant to be included to the source files (using #include directive, in c). Just compile the source files and link them together. Something like
gcc -c main.c
gcc -c encryption.c
gcc main.o encryption.o -o encrypt
or, for shorthand,
gcc main.c encryption.c -o encrypt
Note: If you're bothered about the presence (or absence) of header files while compilation, check the pre-processed output of each source files using gcc -E option.
So I have some trouble using shared libraries in combination with GCC.
I'm quite new to this so that's why I came to ask it here. I was unable to find a question on stack overflow that helps me with mine (maybe i overlooked one). But first something about my setup and what I'm trying to accomplish.
So I have these two libraries that are development parallel to each other. One is named liblinkedlist, which contains the linkedlist implementation in C and the other is named libgraph, containing a graph implementation in C. Both are put in the following folder structure:
<root>
+---graph_lib(folder)
+---build(folder)
+---src(folder)
+---makefile(file)
+---linkedlist_lib
+---build(folder)
+---src(folder)
+---makefile(file)
Each src folder contains the source files (linkedlist.h and .c for liblinkedlist and graph.h and .c for libgraph)
In each build folder the .o and .so files created from the header files are stored.
Now the problem is that I want to use the liblinkedlist.so in /linkedlist_lib/build/ in my graph library. While compiling the libraries everything seems to go well. But when I try to use it in combination with including a header file (which is inside the linkedlist library), I get the message that it could not be found.
My compile commands are the following:
For the liblinkedlist:
gcc -fpic -c src/linkedlist.c -o build/linkedlist.o
gcc -shared -o build/liblinkedlist.so build/linkedlist.o
And for the libgraph wich uses the liblinkedlist:
gcc -fpic -c src/libgraph.c -o build/libgraph.o
gcc -fpic -c src/graph.c -o build/graph.o
gcc -L../linkedlist_lib/build/ -o build/libgraph build/libgraph.o build/graph.o -llinkedlist
These are the command and errors I get when using the header file:
gcc -fpic -c src/libgraph.c -o build/libgraph.o
In file included from src/libgraph.c:2:0:
src/graph.h:4:24: fatal error: linkedlist.h: File or folder does not exist
#include "linkedlist.h"
^
compilation terminated.
make: *** [build/libgraph.o] Fout 1
Any ideas on how to fix this problem, am I doing something wrong here?
Thanks in advance
I'm attempting to use a C library for an opencourseware course from Harvard. The instructor's instructions for setting up the external lib can be found here.
I am following the instructions specific to ubuntu as I am trying to use this lib on my ubuntu box. I followed the instructions on the page to set it up, but when I run a simple helloWorld.c program using a cs50 library function, gcc doesn't want to play along.
Example:
helloWorld.c
#include <stdio.h>
#include <cs50.h>
int
main(void){
printf("What do you want to say to the world?\n");
string message = GetString();
printf("%s!\n\n", message);
}
$ gcc helloWorld.c
/tmp/ccYilBgA.o: In function `main':
helloWorld.c:(.text+0x16): undefined reference to `GetString'
collect2: ld returned 1 exit status
I followed the instructions to the letter as stated in the instructions, but they didn't work for me. I'm runing ubuntu 12.04. Please let me know if I can clarify further my problem.
First, as a beginner, you should always ask GCC to compile with all warnings and debugging information enabled, i.e. gcc -Wall -g. But at some time read How to invoke gcc. Use a good source code editor (such as GNU emacs or vim or gedit, etc...) to edit your C source code, but be able to compile your program on the command line (so don't always use a sophisticated IDE hiding important compilation details from you).
Then you are probably missing some Harvard specific library, some options like -L followed by a library directory, then -l glued to the library name. So you might need gcc -Wall -g -lcs50 (replace cs50 by the appropriate name) and you might need some -Lsome-dir
Notice that the order of program arguments to gcc is significant. As a general rule, if a depends upon b you should put a before b; more specifically I suggest
Start with the gcc program name; add the C standard level eg -std=c99 if wanted
Put compiler warning, debugging (or optimizing) options, eg -Wall -g (you may even want to add -Wextra to get even more warnings).
Put the preprocessor's defines and include directory e.g. -DONE=1 and -Imy-include-dir/
Put your C source file hello.c
Put any object files with which you are linking i.e. bar.o
Put the library directories -Lmy-lib-dir/ if relevant
Pur the library names -laa and -lbb (when the libaa.so depends upon libbb.so, in that order)
End with -o your-program-name to give the name of the produced binary. Don't use the default name a.out
Directory giving options -I (for preprocessor includes) and -L for libraries can be given several times, order is significant (search order).
Very quickly you'll want to use build automation tools like GNU make (perhaps with the help of remake on Linux)
Learn also to use the debugger gdb.
Get the habit to always ask for warnings from the compiler, and always improve your program till you get no warnings: the compiler is your friend, it is helping you!
Read also How to debug small programs and the famous SICP (which teaches very important concepts; you might want to use guile on Linux while reading it, see http://norvig.com/21-days.html for more). Be also aware of tools like valgrind
Have fun.
I take this course and sometimes I need to practice offline while I am traveling or commuting. Under Windows using MinGW and Notepad++ as an IDE (because I love it and use it usually while codding python) I finally found a solution and some time to write it down.
Starting from scratch. Steps for setting up gcc C compiler, if already set please skip to 5
Download Git and install. It includes Git Bash, which is MINGW64 linux terminal. I prefer to use Git as I need linux tools such as sed, awk, pull, push on my Windows and can replace Guthub's terminal.
Once Git installed make sure that gcc packages are installed. You can use my configuration for reference...
Make sure your compiler works. Throw it this simple code,
by saving it in your working directory Documents/Harvard_CS50/Week2/
hello.c
#include <stdio.h>
int main(void)
{
printf("Hello StackOverflow\n");
}
start Git Bash -> navigate to working directory
cd Documents/Harvard_CS50/Week2/
compile it in bash terminal
gcc helloworld.c -o helloworld.exe
execute it using bash terminal
./helloworld.exe
Hello StackOverflow
If you see Hello StackOverflow, your compiler works and you can write C code.
Now to the important bit, installing CS50 library locally and using it offline. This should be applicable for any other libraries introduced later in the course.
Download latest source code file cs50.c and header file cs50.h from https://github.com/cs50/libcs50/tree/develop/src and save them in Documents/Harvard_CS50/src
Navigate into src directory and list the files to make sure you are on the right location using
ls
cs50.c cs50.h
Cool, we are here. Now we need to compile object file for the library using
gcc -c -ggdb -std=c99 cs50.c -o cs50.o
Now using the generated cs50.o object file we can create our cs50 library archive file.
ar rcs libcs50.a cs50.o
After all this steps we ended with 2 additional files to our original files. We are interested in only 2 of them cs50.h libcs50.a
ls
cs50.c cs50.h cs50.o libcs50.a
Copy Library and header files to their target locations. My MinGW is installed in C:\ so I copy them there
cs50.h --> C:\MinGW\include
libcs50.a --> C:\MinGW\lib
Testing the cs50 Library
To make sure our library works, we can throw one of the example scripts in the lecture and see if we can compile it using cs50.h header file for the get_string() method.
#include <stdio.h>
#include <cs50.h>
int main(void)
{
printf("Please input a string to count how long it is: ");
string s = get_string();
int n = 0;
while (s[n] != '\0')
{
n++;
}
printf("Your string is %i chars long\n", n);
}
Compile cs50 code using gcc and cs50 library. I want to be explicit and use:
gcc -ggdb -std=c99 -Wall -Werror test.c -lcs50 -o test.exe
But you can simply point the source, output filename and cs50 library
gcc test.c -o test.exe -lcs50
Here we go, program is compiled using header and methods can be used within.
If you want Notepad++ as an IDE you can follow this tip to set it up with gcc as a compiler and run your code from there.
Just make sure your nppexec script includes the cs50 library
npp_save
gcc -ggdb -std=c99 -Wall -Werror "$(FULL_CURRENT_PATH)" -lcs50 -o "$(CURRENT_DIRECTORY)\$(NAME_PART).exe"
cmd /c "$(CURRENT_DIRECTORY)\$(NAME_PART).exe"
Download the cs50 from: http://mirror.cs50.net/library50/c/library50-c-5.zip
Extract it. (You will get two files cs50.c and cs50.h)
Now copy both the files to your default library folder. (which includes your stdio.h file)
Now while writing your program use: #include < cs50.c >
You can also copy the files to the folder containing your helloWorld.c file.
You have to use: #include " cs50.c ".
OR =====================================================================>
Open cs50.c and cs50.h files in text editor.
In cs50.h, just below #include < stdlib.h > add #include < stdio.h > and #include < string.h > both on new line.
Now open cs50.c file, copy everything (from: /**Reads a line of text from standard input and returns the equivalent {from line 47 to last}) and paste it in cs50.h just above the #endif and save the files.
Now you can copy the file cs50.h to either your default library folder or to your current working folder.
If you copied the file to default folder then use: #include < cs50.h > and if you copied the files to current working folder then use: #include " cs50.h ".
You need to link against the library during compilation. The library should end in .a or .so if you are on Ubuntu. To link against a library:
gcc -o myProgram myProgram.c -l(library name goes here but no parentheses)
You have to link against the library, how come GCC would know what library you want to use?
gcc helloWorld.c -lcs50
Research Sources:
building on the answers above given by Basile Starynkevitch, and Gunay Anach
combined with instructions from some videos on youtube 1 2
Approach:
covering the minimum things to do, and sharing the "norms" separately
avoiding any modification to anywhere else on the system
including the basic breakdown of the commands used
not including all the fine details, covering only the requirements absolute to task or for effective communication of instructions. leaving the other mundane details to the reader
assuming that the other stuff like compiler, environment variable etc is already setup, and familiarity with shell's file navigation commands is there
My Environment:
compiler: gcc via msys2
shell: bash via msys2
IDE: doesnt matter here
Plan:
getting the source files
building the required files: *.o (object) and *.a (archive)
telling the compiler to use it
Action:
Let's say, current directory = "desktop/cs50"
It contains all the *.c files like test-file.c which I will be creating for assignments/problem sets/practise etc.
Get the *.h and *.c files
Source in this particular case: https://github.com/cs50/libcs50/tree/main/src
Go over each file individually
Copy all the content of it
Say using "Copy raw contents" icon of individual files
Create the corresponding file locally in the computer
Do it in a a separate folder just to keep things clean, let's say in "desktop/cs50/src" aka ./src
Build the required files using in the terminal after changing your current directory to "desktop/cs50/src" :
gcc -c cs50.c to create the "cs50.o" object file from "cs50.c" using "gcc"
ar cr libcs50.a cs50.o to create "libcs50.a" archive file which'll be containing "cs50.o" object file
Here, "libcs50" = "lib" prefix + "cs50" name (same as the header file's name)
This is the norm/standard way where the prefix "lib" is significant as well for a later step
However, prefix can be skipped, and it's not compulsory for name to match the header file's name either. Though, Skipping prefix is not recommended. And I can't say for sure about the name part
To tell the compiler to be able to use this infrastructure, the commands will be in following syntax after going to the parent directory (i.e. to "desktop/cs50"):
gcc test-file.c -Isrc -Lsrc -lcs50 if you used "lib" prefix in step 2.2 above
here, -I flag is for specifying the directory of *.h header file included in your test_file.c
and -L flag is for specifying the directory to be used for -l
and -l is for the name of the *.a file. Here the "lib" prefix talked about earlier, and ".a" extension is not mentioned
the order of these flags matter, keep the -I -L -l flags after the "test-file.c"
Some more notees:
don't forget to use the additional common flags (like those suggested above for errors etc)
if you skipped the "lib" prefix, then you can't use -L -l flags
so, syntax for command will become: gcc test-file.c -Isrc src/libcs50.a
say i created my test-file.c file in "desktop/cs50/psets", so, it can be handled in 2 notable ways (current dir = "desktop/cs50/") :
cd psets then changing the relative address correspondingly in -I -L, so result:
gcc test-file.c -I../src -L../src -lcs50
keeping current directory same, but then changing the file's relative address correspondingly, so result:
gcc psests/test-file.c -Isrc -Lsrc -lcs50
or use absolute addresses 😜
as it can be seen that this becomes quite long, that's when build automation tools such as make kick in (though i am accomplishing that using a shell script 😜)