03/15/06, CISC181

What kind of error is this?


> CC testComputeSplitTime5.cc
Undefined                       first referenced
 symbol                             in file
double computeSplitTime(const char*const)      testComputeSplitTime5.o
ld: fatal: Symbol referencing errors. No output written to a.out
>



(1) This is a l__________ing error.


(2) It means that you have a function _____________  but you don't have
a matching function ______________


Fill in the second two blanks with two of the following:

    prototype
    call
    definition


Answer Key:

(1) linking

(2) call ... definition


The same kind of error can occur if you have a file that contains
only function definitions, but no main function, e.g.:

> CC computeSplitTime.cc
Undefined                       first referenced
 symbol                             in file
main                                /opt/SUNWspro/prod/lib/crt1.o
ld: fatal: Symbol referencing errors. No output written to a.out
> 

The way to bring these two together is to separately compile, and then
link the .o files

Start with new fresh directory

> ls
03.15.txt  castAway  csvFiles
> mkdir workoutProject1
> 

change directory into that new directory

> cd workoutProject1/
> 

The following Unix command copies three files that we need from the
"sibling" directory csvFiles.

By sibling, I mean that these directories... the current one, and the
called csvFiles... both share a common parent.

.. means parent directory
. means current directory


> cp ../csvFiles/readWorkoutData3.cc ../csvFiles/computeSplitTime.cc ../csvFiles/testComputeSplitTime5.cc  .
> ls
computeSplitTime.cc  readWorkoutData3.cc  testComputeSplitTime5.cc
> 


We also need workoutData.dat

> cp ../csvFiles/workoutData.dat .
> 


An ls command now gives us everything in the current directory:

> ls
computeSplitTime.cc  readWorkoutData3.cc  testComputeSplitTime5.cc  workoutData.dat
> 


We will now rename a few things



> mv readWorkoutData3.cc readWorkoutData.cc
> mv testComputeSplitTime5.cc testComputeSplitTime.cc
> 


> ls
computeSplitTime.cc  readWorkoutData.cc  testComputeSplitTime.cc  workoutData.dat
> 


Next step, is to create a Makefile to compile all this code and test it.


We use the command "emacs Makefile"

We start with a kind of very "genric empty Makefile"


***********************************************************

# Makefile for workoutProject1
# P. Conrad for CISC181, 03/15/06
# A project to show how to read a CSV file into an array of structs
# also to show how to write a Makefile from scratch


# the BINARIES variable is generally a list of the executable programs
# it is typically a list of the files that have a main() function in them

BINARIES = readWorkoutData testComputeSplitTime


all: ${BINARIES}

clean:
	/bin/rm -f ${BINARIES} *.o core a.out


***********************************************************


The words all and clean are followed by colons, and are in column 1.

That means they are called "targets" in the Makefile

For comments, in a Makefile you use # ... everything after the # is a comment

If I want to declare a variable, I use ALL CAPITALS and I use an assignment
statment with no ; at the end. For instance:

BINARIES = readWorkoutData testComputeSplitTime


Typically a variable has a value that is a string, or a list of filenames

To "use" the value of a variable, you put a $ in front of it, and
put the variable name in either { }  or  (   )

 e.g. ${BINARIES}   or $(BINARIES)


Now readWorkoutData needs to be a combination of readWorkoutData.o
and computeSplitTime.o   So we have to specify that in the Makefile


readWorkoutData: readWorkoutData.o computeSplitTime.o
	${CCC} -o readWorkoutData readWorkoutData.o computeSplitTime.o



cat -vt is how you can check for tabs in your Makefile


So, we find a problem:

> make clean
/bin/rm -f readWorkoutData testComputeSplitTime *.o core
> make
CC    -c  readWorkoutData.cc
CC    -c  computeSplitTime.cc
CC -o readWorkoutData readWorkoutData.o computeSplitTime.o
Undefined                       first referenced
 symbol                             in file
double computeSplitTime(char*)        readWorkoutData.o
ld: fatal: Symbol referencing errors. No output written to readWorkoutData
*** Error code 1
make: Fatal error: Command failed for target `readWorkoutData'
> 

How to find the source of this problem...


(1) The function call is in readWorkoutData.o
    That means we can find the function call in what .cc file?

  Answer: readWorkoutData.cc

(2) grep computeSplitTime *.cc tells us where each occurence of computeSplitTime
lives in all of the .cc files

> grep computeSplitTime *.cc
computeSplitTime.cc:// computeSplitTime.cc
computeSplitTime.cc:// separately compiled computeSplitTime() function
computeSplitTime.cc:double computeSplitTime(const char *  const splitTimePtr)
readWorkoutData.cc:double computeSplitTime(char * splitTimePtr);
readWorkoutData.cc:      workout[i].splitTimeSeconds = computeSplitTime(splitTimePtr);
testComputeSplitTime.cc:// write test cases for the computeSplitTime function
testComputeSplitTime.cc:// split out the computeSplitTime function to a separate file
testComputeSplitTime.cc:double computeSplitTime(const char * const splitTimePtr);
testComputeSplitTime.cc:  double result = computeSplitTime(splitTimePtr);
>