I've just started programming in C and decided to use make to build my sample app. Compiling the files using the GCC command works fine, however, using make fails with an error. If make just executes the gcc command under the hood, I don't see why this is even possible.
Here are the list of files:
makefile.make:
app.o: app.c helper.h
gcc -c app.c
helper.o: helper.h helper.c
gcc -c helper.c
app: app.o helper.o
gcc app.o helper.o -o app
app.c
/*
* file: app.c
*/
#include "helper.h"
int main() {
do_something();
return 0;
}
helper.h
/*
* helper.h
*/
void do_something();
helper.c
/*
* file: helper.c
*/
#include <stdio.h>
#include "helper.h"
void do_something() {
printf("Test\n");
printf("Testsss\n");
}
The Problem: Running "make app" throws the error message
Undefined symbols for architecture x86_64:
"_do_something", referenced from:
_main in app.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [app] Error 1
Things Ive tried that works:
Compiling and Linking manually using gcc (using the commands from
make executed serially)
Using "make app.o" and "make helper.o" then running "gcc app.o helper.o -o app" compiles and links the app correctly
rename "makefile.make" to "makefile" or "Makefile". "app.o" and "helper.o" seems to work but i think thats just make doing its default instructions.
Related
Today I installed the Allegro game programming library for C and I’ve tried to include one of the header files but when I try to execute gcc -I./include example.c -o a.exe in the terminal, I keep on getting this error:
Undefined symbols for architecture x86_64:
"_main", referenced from:
implicit entry/start for main executable
(maybe you meant: __al_mangled_main)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Any ideas? I installed Allegro 5 using the instructions here: https://wiki.allegro.cc/index.php?title=Install_Allegro5_From_GIT/OSX
example.c code:
#include <stdio.h>
#include <allegro5/allegro.h>
int main(int argc, const char *argv[]){
puts(“Hello, world!”);
return 0;
}
You need to link your executable to Allegro.
According to the FAQ, you should add -lallegro to your compile command, or -lallegro -lallegro_main on OSX
You may need other flags, and Allegro 5 uses pkg-config instead of allegro-config, so do pkg-config allegro-5.0 allegro_main-5.0 --cflags --libs to find out.
You can combine this into a compiler command by using backticks, e.g.
$CC -W -Wall `pkg-config allegro-5.0 allegro_main-5.0 --cflags --libs` foo.c -o foo.exe
I have included the openssl/md5.h in my source.
#include <openssl/md5.h>
This is my (part of) my code:
char *pf_generate_pfdhr_string(int firstfree, int numpages)
{
const int md5_digest_len = 16;
char hash[md5_digest_len];
MD5_CTX md5_ctx;
MD5_Init(&md5_ctx);
int hdr_arr[2] = {firstfree, numpages};
MD5_Update(&md5_ctx, hdr_arr, 2*sizeof(int));
MD5_Final(hash, &md5_ctx);
return hash;
}
And this is my output
ranlib build/libpf.a
cc -g -O2 -Wall -Wextra -Isrc -rdynamic tests/pf_tests.c build/libpf.a -o tests/pf_tests
Undefined symbols for architecture x86_64:
"_MD5_Final", referenced from:
_pf_generate_pfdhr_string in libpf.a(pf.o)
"_MD5_Init", referenced from:
_pf_generate_pfdhr_string in libpf.a(pf.o)
"_MD5_Update", referenced from:
_pf_generate_pfdhr_string in libpf.a(pf.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [tests/pf_tests] Error 1
I have included the header file so the compiler knows the function exists. However, it seems unable to find the object files for the md5 library. How can I include it in my build?
If I am using Make, what is the best way to do so?
Thank you.
Check the documentation for your platform. It may be -lcrypto -lssl. It may not be. If your platform supports pkg-config, use pkg-config --libs openssl.
I have 3 files, main.c, lists.c, and lists.h.
Im trying to write a Makefile with all the files are in the same directory:
maman21: lists.c lists.h main.c
gcc -g -Wall -ansi main.c -o maman21 -lm
going to the folder through terminal and using make shows me this message:
gcc -g -Wall -ansi main.c -o maman21 -lm
Undefined symbols for architecture x86_64: "_linkedListWay",
referenced from:
_main in main-C9dUT4.o "_reallocWay", referenced from:
_main in main-C9dUT4.o ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to
see invocation)
make: *** [maman21] Error 1
reallocWay and linkedListWay are to functions I'm using in the file.
Thank you for your help.
You've failed to include the lists.c file in the compiler invocation so it doesn't get built.
It should be:
CFLAGS=-g -Wall -ansi
LDLIBS=-lm
maman21: main.o lists.o
main.o: main.c
lists.o: lists.c lists.h
The above uses implicit Makefile rules, it "knows" how to convert a C file to an object (.o) file.
Also, is it normal for Clang to be called gcc?
I am trying to learn OpenMP, starting with the following simple snippet
#include <stdio.h>
#include <stdlib.h>
int main(void) {
#pragma omp parallel
printf("Hello OpenMP!\n");
return 0;
}
Simply compiling from the command line works:
cls ~/Desktop $ gcc -fopenmp HelloOpenMP.c -o HelloOpenMP
cls ~/Desktop $ ./HelloOpenMP
Hello OpenMP!
Hello OpenMP!
However, I'd like to use Eclipse with CDT. I created a new build configuration "OpenMP" and tried to add the -fopenmp flag under "Miscellaneous", copying the other settings from the "Debug" build configuration.
The build fails with
14:56:16 **** Incremental Build of configuration OpenMP for project HelloOpenMP ****
make all
Building file: ../src/HelloOpenMP.c
Invoking: GCC C Compiler
gcc -O0 -g3 -Wall -c -fmessage-length=0 -fopenmp -MMD -MP -MF"src/HelloOpenMP.d" -MT"src/HelloOpenMP.d" -o "src/HelloOpenMP.o" "../src/HelloOpenMP.c"
Finished building: ../src/HelloOpenMP.c
Building target: HelloOpenMP
Invoking: MacOS X C Linker
gcc -o "HelloOpenMP" ./src/HelloOpenMP.o
Undefined symbols for architecture x86_64:
"_GOMP_parallel_end", referenced from:
_main in HelloOpenMP.o
"_GOMP_parallel_start", referenced from:
_main in HelloOpenMP.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
make: *** [HelloOpenMP] Error 1
So I guess this was not the right place to add the -fopenmp compiler option? What configuration should I use to build with OpenMP?
Add -fopenmp flag to the linker section as well.
I'm working on a C project implementing some generic containers and am having this weird issue when compiling. Here is some sample code that also replicates the error.
foo.h
void fooprint(void);
foo.c
#include "foo.h"
#include <stdio>
void fooprint(void){
printf("bar");
return;
}
main.c
#include "foo.h"
int main(void){
fooprint();
return 0;
}
I compile by typing
gcc main.c -o main
and this is what terminal outputs
Undefined symbols:
"_fooprint", referenced from:
_main in ccfMXGzj.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
I'm compiling this on an OSX system but have also tried compiling on a red hat machine with the same effect.
The solution is probably painfully obvious but I have had multiple friends I'm working with look at this and they couldnt see the problem. I've googled around a lot but most symbol error issues are usually pertaining to objective C.
You need to compile them together:
gcc -Wall -Wextra -o main main.c foo.c
Or maybe make a Makefile ?
all: main
main: main.o foo.o
main.o: main.c
foo.o: foo.c
You have to compile also foo.c into an object file and link all of them together:
gcc -o foo.o foo.c
gcc -o main.o main.c
gcc -o main main.o foo.o
Yes, this is simple, so I recommend you to read a good C book and step these easy steps.