|GNU Make Manual||www.imodulo.com · 2003-04-05|
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make programs in various other systems support a few features that are not implemented in GNU
make. The POSIX.2 standard (IEEE Standard 1003.2-1992) which specifies
make does not require any of these features.
A target of the form
file((entry)) stands for a member of archive file file. The member is chosen, not by name, but by being an object file which defines the linker symbol entry.
This feature was not put into GNU
make because of the nonmodularity of putting knowledge into
make of the internal format of archive file symbol tables. Updating Archive Symbol Directories.
Suffixes (used in suffix rules) that end with the character
~ have a special meaning to System V
make; they refer to the SCCS file that corresponds to the file one would get without the
~. For example, the suffix rule
.c~.o would make the file
n.o from the SCCS file
s.n.c. For complete coverage, a whole series of such suffix rules is required. Old-Fashioned Suffix Rules.
make, this entire series of cases is handled by two pattern rules for extraction from SCCS, in combination with the general feature of rule chaining. Chains of Implicit Rules.
In System V and 4.3 BSD
make, files found by
VPATH search (Searching Directories for Prerequisites) have their names changed inside command strings. We feel it is much cleaner to always use automatic variables and thus make this feature obsolete.
In some Unix
makes, the automatic variable
$* appearing in the prerequisites of a rule has the amazingly strange "feature" of expanding to the full name of the target of that rule. We cannot imagine what went on in the minds of Unix
make developers to do this; it is utterly inconsistent with the normal definition of
In some Unix
makes, implicit rule search (Using Implicit Rules) is apparently done for all targets, not just those without commands. This means you can do:
foo.o: cc -c foo.c
make will intuit that
foo.o depends on
We feel that such usage is broken. The prerequisite properties of
make are well-defined (for GNU
make, at least), and doing such a thing simply does not fit the model.
make does not include any built-in implicit rules for compiling or preprocessing EFL programs. If we hear of anyone who is using EFL, we will gladly add them.
It appears that in SVR4
make, a suffix rule can be specified with no commands, and it is treated as if it had empty commands (Empty Commands). For example:
will override the built-in
.c.a suffix rule.
We feel that it is cleaner for a rule without commands to always simply add to the prerequisite list for the target. The above example can be easily rewritten to get the desired behavior in GNU
Some versions of
make invoke the shell with the
-e flag, except under
-k (Testing the Compilation of a Program). The
-e flag tells the shell to exit as soon as any program it runs returns a nonzero status. We feel it is cleaner to write each shell command line to stand on its own and not require this special treatment.
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