Makefile Syntax: Static library lib$(library).a($objects) - c++

Question

I'm updating some Makefiles to move from Make 3.81 to 3.82. In multiple places, the original author used something like this to build static libs:
all: lib$(library).a($objects)
This seems to build each .o file in turn and insert it into the .a using ar:
g++ -O2 <snip> -o some_obj.o some_cpp.cpp
ar rv libsome_lib.a some_obj.o
etc...
This new make version, though, chokes with:
*** No rule to make target 'libsome_lib.a()', needed by 'all'
Am I safe to replace this shortcut with the way I'm used to doing this:
lib$(library).a: $(objects)
ar -rs lib$(library).a $objects
Thanks.
EDIT
Looks like I need a better Makefile education. Here's a larger excerpt from the original Makefile:
CXXFLAGS += -O2 -g -Wall -Wunused-parameter \
`pkg-config --cflags gthread-2.0 glibmm-2.4 gtkmm-2.4`
libs += `pkg-config --libs gthread-2.0 glibmm-2.4` -lc
%.d: %.cpp
$(SHELL) -ec '$(CXX) -M $(CPPFLAGS) $(CXXFLAGS) $< \
| sed '\''s/\($*\)\.o[ :]*/\1.o $# : /g'\'' > $#; \
[ -s $# ] || rm -f $#'
%.d: %.c
$(SHELL) -ec '$(CXX) -M $(CPPFLAGS) $(CXXFLAGS) $< \
| sed '\''s/\($*\)\.o[ :]*/\1.o $# : /g'\'' > $#; \
[ -s $# ] || rm -f $#'
from_sources = $(patsubst %.c,$(2),$(filter %.c, $(1))) $(patsubst %.cpp,$(2),$(filter %.cpp, $(1)))
sources = $(shell cat sources.inc)
objects = $(call from_sources,$(sources),%.o)
depends = $(call from_sources,$(sources),%.d)
library = some_lib
.PHONY: all clean fresh
all: lib$(library).a($(objects))
clean:
<SNIP>
if neq($(MAKECMDGOALS),clean)
include $(depends)
endif
When this runs under 3.81, I get all the .d dependences created, then make starts g++ing the obj files. Under 3.82, I get the .d files but no .o and make fails with "***No rule to make..."

Answer 1

This is the "archive member" syntax supported in gnu make. It's a bit too intimate with the tools for my tastes, but there it is. The original error may be caused by $(objects) being empty. But I'm really not sure. Here's some documentation:
http://www.gnu.org/software/make/manual/make.html#Archive-Members
11.1 Archive Members as Targets
An individual member of an archive file can be used as a target or
prerequisite in make. You specify the member named member in archive
file archive as follows:
archive(member)
This construct is available only in targets and prerequisites, not in recipes! Most programs that you might use in
recipes do not support this syntax and cannot act directly on archive
members. Only ar and other programs specifically designed to operate
on archives can do so. Therefore, valid recipes to update an archive
member target probably must use ar. For example, this rule says to
create a member hack.o in archive foolib by copying the file hack.o:
foolib(hack.o) : hack.o
ar cr foolib hack.o
In fact, nearly all archive member targets are updated in just this way and there is an implicit rule to
do it for you. Please note: The ‘c’ flag to ar is required if the
archive file does not already exist.

Answer 2

Your way looks good, but there must be more to the old makefile if the old way worked at all.
Oh, and just for good form I'd suggest this:
lib$(library).a: $(objects)
ar -rs $# $^
EDIT
Don't feel bad about not understanding Make very well; it has quite a learning curve.
There is still not quite enough to go on here, but if sources.inc isn't too huge, you could try the following in 3.81 and 3.82 and look for differences:
experiment:
#echo sources: $(sources)
#echo objects: $(objects)
#echo depends: $(depends)
The evidence so far is that objects is empty under 3.82, but if the .d files are being rebuilt under 3.82 that suggests that depends is not empty, which is very strange.

Answer 3

Possibly, but you have no explicit rule for converting something like xyz.cpp to xyz.o, which you may need for your sources before trying to inject their objects into the library. There may be a suitable implicit rule for this so check first.
The first question I'd be asking is: what happened to $objects that caused you to try and target libsome_lib.a() (i.e., with nothing between the parentheses) in the first place?
To be honest, I tend to avoid these encompassing rules as much as possible, preferring explicit statements of dependencies (unless there are a lot of dependencies, of course). Yes, I know it makes the makefiles larger and marks me as at least a partial luddite, but I prefer to have things that just work over things that work cleverly.
Cut'n'paste is one of the strongest tools in my toolbox :-)