compile a foreign .c file

Hello,

I am new to C programming and tried using the Simple Open EtherCAT library (SOEM) on a raspberry Pi. The language used is C.

I pulled the github repository from here (GitHub - OpenEtherCATsociety/SOEM: Simple Open Source EtherCAT Master) on my raspberry Pi. Then I built it as described in the README.md. The file path on my raspberry is now: /home/raspberrypi/SOEM.

I then connected an EtherCAT slave (to be precise, I connected 3: EK1100, EL1809 and EL2809) and then have run the simple_test executable (can be found in: /home/raspberrypi/SOEM/build/test/linux/simple_test) which worked fine. The output I got was without errors and the slave devices were detected.

Then I tried to programm my first own script which should make use of the SOEM functionalities (such as reading out the slaves PDO data). In the folder SOEM there is a simple_test.c file, which can be modified. When compiled, this file should do the exact same thing as the executable simple_test (which was described previously).

However, when I tried compiling the simple_test.c file using
gcc simple_test.c -o simple_test
in the terminal window, it throws an error saying:
fatal error: osal.h: No such file or directory
#include "osal.h"

The error should come from the fact that the program to be compiled does not know where the associated .h files are located. These are mostly under home/raspberrypi/SOEM/soem (however there are other files such as .o files in a different location).

My question is: How do I just manage to tell the program where the linked files are located? Do I have to specify the full file path every time I use the #include "..." command? If I do that, the compilation still throws errors because the needed functions are not found.

Thank you in advance!
Best regards,
Tobias

Did the installation of the SOEM library install any header files in the "/usr/local/include/" or "/usr/include/" directories, then you should include them as

Code:

---

#include <header.h>
// Not as:
#include "header.h"

---

Otherwise, run your compile command as:

Code:

---

gcc -I /path/to/headers/ simple_test.c -o simple_test

---

<header.h> indicates a predefined include path. "header.h" indicates the current directory by default, unless you sue the "-I /path/" gcc option.

You need to tell gcc where the include files are with the -I flag:
-I/path/to/include/files
You need to tell gcc where the library files (.a or .so files) are with the -L flag:
-L/path/to/library/code
And you need to tell it which library file(s) to use with the -l (lowercase L) flag:
-lLIBRARY_FILE_NAME_WITHOUT_EXTENSION

So something like this (note that the -l flag goes last):
gcc -o mycode -I/path/to/include/files -L/path/to/library/code mycode.c -llibrary

Quote:

---

Originally Posted by rstanley

Did the installation of the SOEM library install any header files in the "/usr/local/include/" or "/usr/include/" directories

---

Thank you for your response! Also big thanks to john.c
The installation didn't seem to have installed any header files in the directiories mentioned above. So I guess, I have to define the directory paths manually.

Unfortunately, there are several .h files under different paths. For example, one is in the /home/raspberrypi/SOEM/osal folder, another is under /home/raspberrypi/SOEM/oshw, etc.


Do I then have to manually specify all these paths when compiling?

Quote:

---

Do I then have to manually specify all these paths when compiling?

---

You could pass -I/home/raspberrypi/SOEM and then specify header files like:

Code:

---

#include "osal/whatever"
#include "oshw/whatever"

---

@john.c

I now tried the following code:

gcc simple_test.c -o simple_test -I/home/raspberrypi/SOEM/osal -I/home/raspberrypi/SOEM/osal/linux -I/home/raspberrypi/SOEM/oshw/linux -L/home/raspberrypi/SOEM/osal/linux/osal.c -L/home/raspberrypi/SOEM/oshw/linux/oshw.c

But this threw out the following error code:
/usr/bin/ld: /tmp/cclThXAw.o: in function `simpletest':
simple_test.c: (.text+0x34): undefined reference to `ec_init'
/usr/bin/ld: simple_test.c: (.text+0x54): undefined reference to `ec_config_init'
/usr/bin/ld: simple_test.c: (.text+0x7c): undefined reference to `ec_config_map'
/usr/bin/ld: simple_test.c: (.text+0x80): undefined reference to `ec_configdc'
/usr/bin/ld: simple_test.c: (.text+0x98): undefined reference to `ec_statecheck'
/usr/bin/ld: simple_test.c: (.text+0x1b4): undefined reference to `ec_send_processdata'
/usr/bin/ld: simple_test.c: (.text+0x1bc): undefined reference to `ec_receive_processdata'
/usr/bin/ld: simple_test.c: (.text+0x1c4): undefined reference to `ec_writestate'
/usr/bin/ld: simple_test.c: (.text+0x1d0): undefined reference to `ec_send_processdata'
/usr/bin/ld: simple_test.c: (.text+0x1d8): undefined reference to `ec_receive_processdata'
/usr/bin/ld: simple_test.c: (.text+0x1e8): undefined reference to `ec_statecheck'
/usr/bin/ld: simple_test.c: (.text+0x240): undefined reference to `ec_send_processdata'
/usr/bin/ld: simple_test.c: (.text+0x248): undefined reference to `ec_receive_processdata'
/usr/bin/ld: simple_test.c: (.text+0x340): undefined reference to `osal_usleep'
/usr/bin/ld: simple_test.c: (.text+0x378): undefined reference to `ec_readstate'
/usr/bin/ld: simple_test.c: (.text+0x444): undefined reference to `ec_ALstatuscode2string'
/usr/bin/ld: simple_test.c: (.text+0x49c): undefined reference to `ec_writestate'
/usr/bin/ld: simple_test.c: (.text+0x4b4): undefined reference to `ec_close'
/usr/bin/ld: simple_test.c: (.text+0x4e4): undefined reference to `ec_slavecount'
/usr/bin/ld: simple_test.c: (.text+0x4f8): undefined reference to `ec_slave'
/usr/bin/ld: simple_test.c: (.text+0x4fc): undefined reference to `ec_group'
/usr/bin/ld: simple_test.c: (.text+0x528): undefined reference to `ec_DCtime'
/usr/bin/ld: /tmp/cclThXAw.o: in function `ecatcheck':
simple_test.c: (.text+0x620): undefined reference to `ec_readstate'
/usr/bin/ld: simple_test.c: (.text+0x74c): undefined reference to `ec_writestate'
/usr/bin/ld: simple_test.c: (.text+0x7c8): undefined reference to `ec_writestate'
/usr/bin/ld: simple_test.c: (.text+0x810): undefined reference to `ec_reconfig_slave'
/usr/bin/ld: simple_test.c: (.text+0x8b0): undefined reference to `ec_statecheck'
/usr/bin/ld: simple_test.c: (.text+0x99c): undefined reference to `ec_recover_slave'
/usr/bin/ld: simple_test.c: (.text+0xa98): undefined reference to `osal_usleep'
/usr/bin/ld: simple_test.c: (.text+0xab0): undefined reference to `ec_group'
/usr/bin/ld: simple_test.c: (.text+0xab8): undefined reference to `ec_slave'
/usr/bin/ld: simple_test.c: (.text+0xad4): undefined reference to `ec_slavecount'
/usr/bin/ld: /tmp/cclThXAw.o: in function `main':
simple_test.c: (.text+0xb18): undefined reference to `osal_thread_create'
/usr/bin/ld: simple_test.c: (.text+0xb4c): undefined reference to `ec_find_adapters'
/usr/bin/ld: simple_test.c: (.text+0xb8c): undefined reference to `ec_free_adapters'
collect2: error: ld returned 1 exit status

I guess I -L-flagged the wrong library files. But I don't have any .a or .so files, only .c.o files found under /home/raspberrypi/SOEM/build/CMakeFiles/soem.dir.
Should I use these? Is compiling code any different with CMake?

I have also found another folder under the following path:

/home/raspberrypi/SOEM/build/test/linux/simple_test/CMakeFiles/simple_test.dir

in this folder, there are several files like "DependInfo.cmake" or "depend.make", "depend.internal", etc.
Could I make use of these to compile my code more easily?

First, go back and insure that you compiled and installed SOEM correctly with no errors reported. Then examine the Tutorial.

Good luck!

Did you execute sudo make install from the build directory?
If not, do so.

Once you've installed it, you should refer to the header files in your source code like this:

Code:

---

#include <soem/osal.h>
#include <soem/oshw.h>

---

Then compile like this:

Code:

---

gcc yourprog.c -o yourprog -lsoem

---

(Note that -l is a lowercase L)