Intel XENIX 286 Programmers Guide (86) - Tenox.tc

make: Program Maintainer XENIX Programming
The most com mon use of the library naming convention is to create a makefile that
automatically maintains an archive library. For example, the following dependency
lines define the commands required to create a library, named lib, containing up · to date
versions of the files filel.o, file2.o, and file3.o.
lib:
.c. a:
lib(file1.o) lib(fi le2.o) lib(file3.o)
@echo lib is now up to date
$(CC) -c $(CFLAGS) $<
ar rv $@ $*.o
rm -f $*.o
The .c.a rule shows how to redefine a built-in rule for a library. In the following
example, the built-in rule is disabled, allowing the first dependency to create the
library.
lib:
.c.a:;
lib(file1.o) lib(file2.o) lib(fi le3.o)
$(CC) -c $(CFLAGS) $(?: .o = .c)
ar rv lib $?
rm $?
@echo lib is now up to date
In this example, a substitution sequence is used to change the value of the $? macro
from the names of the object files "filel.o", "file2.o", and "file3.o" to "filel.c", "file2.c",
and "file3.c".
Troubleshooting
Most difficulties in using make arise from make's specific meaning of dependency. If
the file x.c has the line
#include "defs"
then the object file x.o depends on defs; the source file x.c does not. (If defs is changed,
it is not necessary to do anything to the file x.c, while it is necessary to recreate x.o.)
To determine which commands make will execute, without actually executing them, use
the -n option. For example, the command
make -n
prints out the commands make would normally execute without actually executing them.
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