Hi;
Can someone explain why, when I use 'make' cmd in processing code composed of list.c, list.h, and p1704.c (note that my 'make' cmd has following switches:
)
I get the following failed terminal output:
[CODE/home/jharvard/prata/prata17/p1704.c:15: undefined reference to `InitializeList'
/home/jharvard/prata/prata17/p1704.c:16: undefined reference to `ListIsFull'
/home/jharvard/prata/prata17/p1704.c:30: undefined reference to `AddItem'
/home/jharvard/prata/prata17/p1704.c:35: undefined reference to `ListIsFull'
/home/jharvard/prata/prata17/p1704.c:43: undefined reference to `ListIsEmpty'
/home/jharvard/prata/prata17/p1704.c:48: undefined reference to `Traverse'
/home/jharvard/prata/prata17/p1704.c:50: undefined reference to `ListItemCount'
/home/jharvard/prata/prata17/p1704.c:53: undefined reference to `EmptyTheList'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: Nothing to be done for `list.c'.
CODE]
yet, if I compile only with:
my code compiles just fine.

I have only a simple guide to Linux, and an internet search of the initial error "output" told me that I leaft out libraries, which was not at all the case.
Thanks

it is not related to linux but to the compiler you use. This message means you use something named ListIsEmpty or Traverse but you have not defined it. Usually it means you missed to include a header file containing that information. These messages are warnings, the compiler assumes some defaults, therefore it will be able to produce a result. Using -Wall -Werror means you want to stop in case of such warnings therefore your command will fail.

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Double what pan64 says and I believe if you use -Wall you'll see your warnings, the -Werror will cause the compile to interpret all warnings as failures. I recommend that and a few other flags. I believe that you ought to remove all warnings. To me the undefined references are pretty serious problems; but I do realize it's possible to have those warnings and not have execution problems.

Review the manpage or online documentation for gcc, this is where those flags are described.

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Thanks for the replies from all. What I still don't understand is that allof the functions are defined in the .h file, with code in the .c file, and function calls in the "main" file. Additionally, I note that the terminal window flagged ALL functions in the code as "undefined reference": not as if I erred with 1 or 2. It's like it wasn't linking the .h file???

You need an include path reference, the -I flag, even if it is just:One of my simple Makefiles looks something more like this: Note the -I. in the CFLAGS, this tells GCC to reference my working directory for include files.

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Well, is it?
One thing I noticed is that your second command is bringing in list.c, while the first command is not.

The command line used was actually What was listed is my compilers compilation equivalent for "make", which seems to have left out the list.c file

I guess that was missing from my pre-configured "make" command so that it didn't work. I'll have to see what happens when I run clang with -Wall & -Werror to see if that fails to compile (with or without -I).

Guess the problem is that you came from java (or similiar). Compilation did use 'list.h', but at linkage you still have to specify 'list.o' as a part of the project:

I've never heard of a compiler linking a header (.h) file. The compiler uses the file for reference so that it can see the 'signatures' of the functions, and compares these to how they are called (in .c files).

Also, earlier it was hinted that an "undefined reference" was due to a header file not being referenced or found; that too is incorrect information. An "undefined reference" means that the linker (not the compiler) was unable to reference a particular function.

Lastly, another piece of information that is slightly incorrect is that one needs to specify a -I. to look for headers in the current directory. This is only true if including a local header file using the angle-brackets (e.g. #include <list.h> ). The OP has not posted any code, but my bet is that he is including the header file using double-quotes (e.g. #include "list.h" ), and thus the -I. option is not required. If his header file were in a different location other than the current directory, then regardless of whether using double-quotes or the angle-brackets, then the -I<path> option would be needed.

In conclusion, what the OP needs to do (in his Makefile) is to generate individual object files for each of his source code files, and then afterwards link them together to form the executable file. He can generate the object file for each source file using the -c option.

EDIT:

Something like this:
Note the -L option; this indicates that the library 'cs50' is present in the current directory. If it is not, then modify the path to the correct location.

If you have further problems, please post your Makefile within [code][/code] tags.

Another recommendation if you ever have a question as to whether an include file or part of a source file is being compiled, put an obvious syntax error within that file and you should see immediately that failure in your next compilation. If you don't, then something is not happening which you thought was. The include file is not "compiled" but it would be parsed by the compiler.

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No java: just trying to learn C from a text (Prata) and an online course (which provided a compiler with a pre-configured "make" file.
This info was obtain via internet search for "clang undefined reference". Either not satisfactory search criteria, or inadequate knowledge on my part for understanding the full meaning of the answer.
Correct bet!
no Makefile with this particular code, though I've had other programs with Makefile included. I'll have to learn a lot more about compilation switches before making my own Makefile(s). This was simply code from the text, intended for linking by the compiler

Would be nice to post your source files - if possible. Or at least the #include lines ....

Just noticing that your original posting shows that you're compiling p1703.c however the complaints are in p1704.c. So I recommend you post all the code in question. I understand that you're not using a Makefile, so what is the clang command mapped too? Is that a certain compiler? If so, then run that command with a version argument to print out what that exact compiler is or see if it is a symbolic link pointing to something like gcc.

Also, just look at the warnings you have, it says there are undefined references to various symbols. Well, where are those symbols defined?

Please post code in [code][/code] tags.

I had a similar question a few months ago. Here's what I found... http://clang.llvm.org/

When I purchased a Mac OS X system (for Xmas), it included clang with the Xcode package.

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