I'm trying to use this C library using gcc Apple LLVM version 8.0.0 (clang-800.0.42.1) on macOS Sierra. I've done the following steps:
make libquirc.so
Copied libquirc.so into my project directory
gcc -o quirc_test quirc_test.c -L. -l libquirc.so.1.0
It produces the error:
quirc_test.c:1:10: fatal error: 'quirc.h' file not found
#include <quirc.h>
^
1 error generated.
quirc_test.c
#include <quirc.h>
This is the first time I've tried to do anything in C and other related questions about compiling with the link flag didn't seem to help as seen above.
C is somewhat primitive. Shared object libraries do not contain the declaration of the API they implement - at least not in enough detail or a form that the compiler can understand.
You'll need the header file quirc.h somewhere you can find it. You could just copy it into the current directory just like the library, but you'll need a minor adjustment to the include statement.
#include "quirc.h"
If the included file is surrounded by double quotes instead of angle brackets, it will first look in the source code directory instead of the system header directories.
An alternative is to install the library somewhere e.g. /usr/local. Your library would go in /usr/local/lib nd your header in /usr/local/include. If you do that, use the -I directive on the compiler command line to tell the compiler where to look for the header e.g.
cc -I/usr/local/include -L/usr/local/lib -lquirc quirc_test.c
I am trying to compile a C program that requires Image Magick's MagickWand.h:
#include "wand/MagickWand.h"
But my Image Magick was installed through Homebrew on my Mac so I changed the include to the actual location:
#include </usr/local/Cellar/imagemagick/6.8.9-7/include/ImageMagick-6/wand/MagickWand.h>
However, when I compiled the program I received the following error:
/usr/local/Cellar/imagemagick/6.8.9-7/include/ImageMagick-6/wand/MagickWand.h:71:10: fatal error: 'wand/method-attribute.h' file not found
#include "wand/method-attribute.h"
Now I've been going into the .h files when this error crops up and changing their #includes so that they are pointed correctly (because that appears to be the problem), but there is always a new error here and I'd rather not spend hours manually updating these because of a Homebrew install. Does anyone have any suggestions on how to fix this without manually updating each file? I'm not sure exactly what the problem is so perhaps there is a more elegant solution.
Your code should include the MagickWand library as system headers, and keep the generic path. This will keep your future compiling from breaking when the system/library updates.
#include <wand/MagickWand.h>
Tell your C compiler where homebrew installed ImageMagick by setting the preprocessor include flag -I, and linking/library options with the -L & -l flags.
example:
clang -I/usr/local/Cellar/imagemagick/6.8.9-7/include/ImageMagick-6 \
myProject.c -o myProject.o \
-L/usr/local/Cellar/imagemagick/6.8.9-7/lib \
-lMagickWand-6.Q16 \
-lMagickCore-6.Q1
To simplify the whole process, ImageMagick ships MagickWand-config utility. This will take care of libs, includes, and definitions for you.
example:
CFLAGS=$(MagickWand-config --cflags)
LFLAGS=$(MagickWand-config --libs)
clang $CFLAGS myProject.c -o myProject.o $LFLAGS
I installed libsrtp on my ubuntu machine according to the directives in read me, the tests worked fine, and the rptw utility included in libsrtp worked perfectly too. But when I tried to include srtp.h in my HelloWorld! program, it gives me an error that:
fatal error: srtp.h: No such file or directory
compilation terminated.
Concretely, my main file is this
#include "srtp.h"
int main()
{
return 0;
}
My libsrtp.a is present in /usr/local/lib/lib
I used this gcc statement from this blog:
gcc -static main.c -L/usr/local/lib/lib/ -llibsrtp -o main
I will be deeply grateful for any help.
You've found your libsrtp.a , but where is srtp.h ? You'll need to tell the compiler where to search for included files if it's not in a standard location with the -I flag.
Perhaps you need a -I/usr/local/include or -I/usr/local/include/srtp
Note also that -llibsrtp is likely wrong, you need to give the name without the lib prefix. So that makes it -lsrtp
I installed on windows curl 7.28.0 from curl-7.28.1-devel-mingw32.zip through minGW console to default directory like:
./config && make && make install
All needed headers (aka curl.h, types.h ...) I see in C:\MinGW\msys\1.0\local\include\curl
libcurl.pc placed in C:\MinGW\msys\1.0\local\lib\pkgconfig\
libcurl.a, libcurl.dll.a and libcurl.la placed in C:\MinGW\msys\1.0\local\lib.
My download_file.c file includes are:
...
#include <curl/curl.h>
#include <curl/types.h>
#include <curl/easy.h>
...
I try to compile the C code with followed command through gcc:
$ gcc -IC:/MinGW/msys/1.0/include/
-IC:/MinGW/msys/1.0/local/include/curl
-IC:/MinGW/msys/1.0/local/lib/pkgconfig
-o download_file download_file.c -llibcurl -lcurl
with absolute path get the same error:
gcc -I/include/
-I/local/include/curl
-I/local/lib/pkgconfig
-o download_file download_file.c -llibcurl -lcurl
But I still get an error:
download_file.c:21:23: fatal error: curl/curl.h: No such file or directory compilation terminated.
row 21 is #include <curl/curl.h>
What I did wrong? Please help.
You have the curl/ directory in the source code, but also in the option.
It seems the option should point out the higher-level directory in which curl/ is, so it should be something like:
-I/local/include/
I think the problem is likely that you give your include paths on the command line in the Win32 path format. This is not the same as the one used by msys (or ultimately Cygwin).
Try these:
$ gcc -I/include/
-I/local/include/curl
-I/local/lib/pkgconfig
...
Hope I got the absolut paths right, but you can check in your msys shell.
What ticked me off was that you use ./config, which wouldn't work from the Command Prompt, but works from the msys shell. So you need to give paths that all the programs in MinGW understand.
Basically, most programs in MinGW only have the concept of a single file system root, like on any unixoid system, while Win32 has multiple (the drive letters). Since the MinGW programs are linked accordingly, you need to give paths that they understand.
Thank you very much to #0xC0000022L and #unwind. By your help I fixed my problem.
0xC0000022L you are right about absolute path
unwind you are right about -I/local/include/ instead -I/local/include/curl
I found other problem: -L/local/lib instead -I/local/lib.
So this is a working command:
gcc -I/include/
-I/local/include
-L/local/lib
-o download_file download_file.c -llibcurl -lcurl
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 😜)