Why Ceedling can't link the functions from other source files together?

[AhmedMagdy111]

I've used a ChatGPT example that generates the same error in the original code.
🧨 NOTE: The linking error is intermittent; sometimes the build works correctly, and sometimes it doesn't. It's unclear why the error occurs occasionally and then resolves itself at other times.

1. Set Up the Project
First, install Ceedling and create a new project:

bash
gem install ceedling
ceedling new project_name
cd project_name
This will create a basic Ceedling project structure.

2. Create C Files
Let's assume you have 4 C files:

file1.c
file2.c
file3.c
file4.c
Each file will contain simple functions, and you'll link them together.

file1.c
#include "file1.h"

int function_file1() {
return 1;
}

file1.h
#ifndef FILE1_H
#define FILE1_H

int function_file1();

#endif

file2.c
#include "file2.h"
#include "file1.h"

int function_file2() {
return function_file1() + 2;
}

file2.h
#ifndef FILE2_H
#define FILE2_H

int function_file2();

#endif

file3.c
#include "file3.h"
#include "file2.h"

int function_file3() {
return function_file2() + 3;
}

file3.h
#ifndef FILE3_H
#define FILE3_H

int function_file3();

#endif

file4.c
#include "file4.h"
#include "file3.h"

int function_file4() {
return function_file3() + 4;
}

file4.h
#ifndef FILE4_H
#define FILE4_H

int function_file4();

#endif

3. Write Tests
Now, let's create tests for these functions. You can place your test files in the test folder. We'll write one test file that tests the linked functions.

test_file1.c

#include "unity.h"
#include "file1.h"
#include "file2.h"
#include "file3.h"
#include "file4.h"

void setUp(void) {
// Code to set up before each test (if needed)
}

void tearDown(void) {
// Code to clean up after each test (if needed)
}

void test_function_file1(void) {
TEST_ASSERT_EQUAL(1, function_file1());
}

void test_function_file2(void) {
TEST_ASSERT_EQUAL(3, function_file2());
}

void test_function_file3(void) {
TEST_ASSERT_EQUAL(6, function_file3());
}

void test_function_file4(void) {
TEST_ASSERT_EQUAL(10, function_file4());
}

4. Configure Ceedling to Include All Files
In the project.yml file, you need to make sure all C files are included in the build process. By default, Ceedling should include files from the src directory, but you may need to ensure the test files are linked properly.

Make sure the :test_files section in project.yml is correctly set:
test_files:

• test/test_file1.c

5. Run Tests
After everything is set up, run the Ceedling tests:

ceedling test:all
Expected Output
Ceedling should compile the files and run the tests, showing you something like:
Test 'test_function_file1' passed.
Test 'test_function_file2' passed.
Test 'test_function_file3' passed.
Test 'test_function_file4' passed.

The actual Result:
🧨 EXCEPTION: 'Default Test Linker' (gcc) terminated with exit code [1] and output >>
/usr/bin/ld: build/test/out/test_file1_2/file2.o: in function function_file2': /home/Z/Code/Test_Linker/src/file2.c:5:(.text+0xe): undefined reference to function_file1'
collect2: error: ld returned 1 exit status
🌱 Ceedling could not complete operations because of errors

[AhmedMagdy111]

I've noticed something that might help but i can't get why. The error is produced when having multiple test files that include any .h files.

[Letme]

YOu have just 1 test file in above example - so that is not the case. What you have here is also a fairly bad test as you include all the files without mocking anything and you operate on local variables on stack.

Usually what you do is you unit test a header file and mock any sub header files.

[AhmedMagdy111]

I’ve updated it to better reflect my inquiry. I understand the typical process, but in my case, I’m using it to test a state machine and generate coverage reports for specific functions. The challenge comes from having a large file structure to test. What I’m trying to understand is why the linker sometimes fails to reference the compiled functions when there are multiple test files involved.

[Letme]

Easiest way is to run with --verbosity=4 and then your gcc commands get printed in console. Then you will see what you are missing.

Do you clobber between each test or you leave the build folder intact and just run it again? Then leftovers from previous test run might mean that ceedling does not extract headers correctly (or overwrites them).

[AhmedMagdy111]

yes of course i use clobber

[Letme]

Why is this a discussion and not an issue? What do you want to discuss about? That ChatGPT is not giving you complete project.yml configuration?

[AhmedMagdy111]

The reason this is a discussion and not an issue is because I’m trying to understand why the linker intermittently fails to reference compiled functions in my setup. I’ve already tested several solutions, but the problem persists, and I’m seeking insights into potential underlying causes or configurations I might be missing.

[Letme]

You did not paste any configuration - at least not relevant to includes/linking.

[AhmedMagdy111]

I didn't as i use default configurations in the example.

[AhmedMagdy111]

I just created empty .h files—one for each .c file that needs to be compiled—and included them in the testing file. Everything is referenced correctly, so why do I need to include the .h files to make the .c files compile? Why doesn't it compile all the files in the source configuration automatically?

[mvandervoord]

Hi @AhmedMagdy111 -- Ceedling lets you specify which files are needed for a given test in two ways. You can use either or both in each test file. Both are specified in the test file itself!

• You can #include a header, and if there is a corresponding c file, it will be added to the list of things to be compiled & linked.
• You can use the macro TEST_SOURCE_FILE("blah.c") to tell Ceedling you want blah.c to be compiled / linked with this test.

The configuration in the yaml file tells ceedling where to find ALL the source files and includes. Each test, however, becomes its own executable (to maximize testing potential with mocks, etc). In this way, we are able to give the test developer fine control of what is tested.

[AhmedMagdy111]

Thanks for the clarification. That was helpful. Thanks!