The compilation of code involves several steps:
The linking step assembles the various routines produced by the compiler during the compilation step, and resolves missing calls to either language-specific libraries or system-wide functions.
We will use the GNU C compiler for this course because it is (a) free and (b) more efficient than the Sun equivalent. This compiler is invoked via the gcc command. Typing
gcc fname.cwill compile the file fname.c, linked it to the default libraries and produce an executable file called by default a.out.
Several parameters may be used to modify the default in the compilation. Some of these are:
-o out_file specify the output file (executable, or binary) to be out_file -O, -O1, -O2, -O3 specify optimization level -c fname.c indicates that you only want to compile the file fname.c, in which case the output file will be fname.o -lname links with the library libname.a -Ldirectory directs gcc to look for libraries in directory, in addition to the standard system library path
We strongly advise that you omit optimization until you are sure a program works. Optimizers tend to change the code around internally for the sake of efficiency, and they can make it extremely difficult to find errors in a complicated program. In addition, many have been known to introduce bugs of their own...
We also maintain the following aliases on newton to facilitate your compilations:
C fname will compile and link the C program in the file fname.c with the standard C mathematics library, placing the executable in fname Cgfx will compile the code in fname.c, then link it with the standard C mathematics library and the xutility graphics library. This library contains (among other things) a set of plotting functions written by Biao Lu (a former graduate student who left us in 1994) which form the basis for much of the graphics we will need to do during the quarter.