Mex compilation with header files

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Sumeet
Sumeet on 15 Jan 2013
Commented: Letian Wang on 29 Jan 2015
Hi,
I'm running Matlab on Ubuntu 12.04. I have written a C++ function simulation.cpp using the mex format. I've defined some of my functions in a separate header file that is located in the same directory as simulation.cpp. I read on the web that to compile a .cpp file with header files, I need to use -l and provide the path of the header files. When I run the following:
mex -l"/media/.../folder_containing_header_files" simulation.cpp
I get the following error
/usr/bin/ld: cannot find -l/media/.../folder_containing_header_files/
collect2: ld returned 1 exit status
mex: link of ' "simulation.mexglx"' failed.
Incidentally, all my header files are located in the same directory as simulation.cpp, which is also my working directory in matlab.
Does anybody know what the problem is?
Thanks!

Answers (5)

Sumeet
Sumeet on 17 Jan 2013
Thank You all for your help.
James: I do have all my header files in one folder. When I tried without the -I as you suggested, I was getting an undefined reference error for all functions declared in my header file and defined in a separate cpp file (with the same name as the header file). Some web-searching revealed that I shouldn't be doing just
mex simulation.cpp
but instead
mex simulation.cpp header.cpp
This worked. Sorry if this is well-known, I wasn't aware of this - I don't have a CS or compilers background.
Thanks again James, Walter and Ryan!
  1 Comment
Letian Wang
Letian Wang on 29 Jan 2015
Hi, I am also having this problem. But I did have a header.hpp file, and it could not be recognized by matlab.
So how can you make it? turn it into cpp file?
Thank you for sharing!

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Walter Roberson
Walter Roberson on 15 Jan 2013
You used the "-l" (lower-case L) option; you need to use "-I" (upper-case I). "I" for "include".
Also you might need to use a space between the option and its value.
  1 Comment
Sumeet
Sumeet on 15 Jan 2013
Edited: Sumeet on 15 Jan 2013
Thanks again Walter. Yes, -I (I for include) was the problem. However, now it cannot find mex.h. Where is it located and how do I specify its location to matlab?
>> mex -I "./" simulation.cpp
Warning: You are using gcc version "4.6.3-1ubuntu5)". The version
currently supported with MEX is "4.4.6".
For a list of currently supported compilers see:
http://www.mathworks.com/support/compilers/current_release/
simulation.cpp:2:17: fatal error: mex.h: No such file or directory
compilation terminated.
mex: compile of ' "simulation.cpp"' failed.
Error using mex (line 206)
Unable to complete successfully.

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James Tursa
James Tursa on 15 Jan 2013
If your current directly is the directory that contains simulation.cpp and its associated header files, doesn't simply "mex simulation.cpp" work at the command line?
  3 Comments
Sumeet
Sumeet on 15 Jan 2013
Thanks James and Walter. I tried both `<HeaderFile.hpp> and "HeaderFile.hpp". It didn't help.
Walter Roberson
Walter Roberson on 15 Jan 2013
Are you still using -l (lower-case L)? I'm sure it should be -I (upper-case I)

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James Tursa
James Tursa on 15 Jan 2013
Edited: James Tursa on 15 Jan 2013
Have you tried the function form of mex yet? I.e., something like
mex('-I','...whatever...','simulation.cpp')
Also, what do your include lines in the actual source code look like?
  7 Comments
James Tursa
James Tursa on 17 Jan 2013
Edited: James Tursa on 17 Jan 2013
Frankly, I don't know for sure since I don't personally use any of these library/include/directory options myself. Things like having spaces in directory names etc tend to complicate things, so I avoid these options entirely. But I have never had a problem with the following approach:
- Have all the source and header files in one directory
- Make that directory the current directory
- Use simple #include "filename.h" syntax in source files
- Use filenames without directory info on the mex command line
Does this approach work for you?
Walter Roberson
Walter Roberson on 17 Jan 2013
If you were to try
mex -v gateway.c
then along the way it would probably indicate which directories it is -I'ing; you could then -I those directories for your actual code.

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Ryan Livingston
Ryan Livingston on 17 Jan 2013
There should be no space between the switch and the directory. So can you try:
mex -I./ gateway.c
rather than
mex -I "./" gateway.c

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