Makefile Implicit Rules

Compiling C programs

n.o is made automatically from n.c with a command of the form `$(CC) -c $(CPPFLAGS) $(CFLAGS)'.

Compiling C++ programs

n.o is made automatically from n.cc, n.cpp, or n.C with a command of the form `$(CXX) -c $(CPPFLAGS) $(CXXFLAGS)'. We encourage you to use the suffix `.cc' for C++ source files instead of `.C'.

Compiling Pascal programs

n.o is made automatically from n.p with the command `$(PC) -c $(PFLAGS)'.

Assembling and preprocessing assembler programs

n.o is made automatically from n.s by running the assembler, as. The precise command is `$(AS) $(ASFLAGS)'.

n.s is made automatically from n.S by running the C preprocessor, cpp. The precise command is `$(CPP) $(CPPFLAGS)'.

Linking a single object file

n is made automatically from n.o by running the linker (usually called ld) via the C compiler. The precise command used is `$(CC) $(LDFLAGS) n.o $(LOADLIBES) $(LDLIBS)'.

This rule does the right thing for a simple program with only one source file. It will also do the right thing if there are multiple object files (presumably coming from various other source files), one of which has a name matching that of the executable file. Thus,

          x: y.o z.o
  

when x.c, y.c and z.c all exist will execute:

          cc -c x.c -o x.o
       cc -c y.c -o y.o
       cc -c z.c -o z.o
       cc x.o y.o z.o -o x
       rm -f x.o
       rm -f y.o
       rm -f z.o
  

In more complicated cases, such as when there is no object file whose name derives from the executable file name, you must write an explicit command for linking.

Each kind of file automatically made into `.o' object files will be automatically linked by using the compiler (`$(CC)', `$(FC)' or `$(PC)'; the C compiler `$(CC)' is used to assemble `.s' files) without the `-c' option. This could be done by using the `.o' object files as intermediates, but it is faster to do the compiling and linking in one step, so that's how it's done.