Argh, ignore that last comment, I'm indeed missing something obvious ;) patching Makefile.in and still thinking automake should get things right is not exactly right.

Note to self: Don't post bug reports after 48 hours of uninterrupted coding ;)

I've added a new special variable, .FEATURES, to GNU make.  You can check it's contents for the word "second-expansion" to see if the extra $ quoting is required:

  ifneq (,$(filter second-expansion,$(.FEATURES)))
    # Supports secondary expansion
  endif

In a future version of GNU make we will work out a more comprehensive quoting mechanism that can be used to avoid these issues more straightforwardly (I hope).

This doesn't technically fix the regression, unfortunately :-/.

I checked libjava's Makefile.am. It boils down to the following lines:


inner_nat_headers = java/io/ObjectOutputStream$$PutField.h \
java/io/ObjectInputStream$$GetField.h \
java/lang/reflect/Proxy$$ProxyData.h \
java/lang/reflect/Proxy$$ProxyType.h \
gnu/java/net/PlainSocketImpl$$SocketInputStream.h \
gnu/java/net/PlainSocketImpl$$SocketOutputStream.h

It is easy to fix just for 3.81 but the solution that works for both 3.80 and 3.81 is somewhat involved. Here is an example makefile that shows the technique:

make_version := $(shell $(MAKE) -v | sed -e 's/GNU Make \([0-9]\+\.[0-9]\+\).*/\1/;q')
make_version_major := $(shell echo $(make_version) | sed -e 's/\([0-9]\+\)\..*/\1/')
make_version_minor := $(shell echo $(make_version) | sed -e 's/.*\.\([0-9]\+\)/\1/')

has_second_expansion := $(shell test $(make_version_major) -gt 3 -o \
  $(make_version_major) -eq 3 -a $(make_version_minor) -gt 80 && echo 1)

ifdef has_second_expansion
define escape-dollar-sign
$(subst $$,$$$$,$1)
endef
else
define escape-dollar-sign
$1
endef
endif


foo_target := foo$$bar
foo_prereq := $(call escape-dollar-sign,$(foo_target))

.PHONY: all $(foo_prereq)

all: $(foo_prereq)
        @echo '$<'

$(foo_target):
        @echo '$@'

Note the two variables, foo_target and foo_prereq, that are used respectively to for defining foo as a target (one expansion) and for using it as a prerequisite (two expansions).

In case of libjava, the

In libjava's case, the inner_nat_headers variable is used only to define prerequisites so its content can simply be run through escape-dollar-sign, e.g.,

inner_nat_headers := java/io/ObjectOutputStream$$PutField.h \
java/io/ObjectInputStream$$GetField.h \
java/lang/reflect/Proxy$$ProxyData.h \
java/lang/reflect/Proxy$$ProxyType.h \
gnu/java/net/PlainSocketImpl$$SocketInputStream.h \
gnu/java/net/PlainSocketImpl$$SocketOutputStream.h

inner_nat_headers := $(call escape-dollar-sign,$(inner_nat_headers))

Note the use of `:=' instead of `='.

Since this test requires GNU make anyway, it can be done with simply-expanded variables.  Instead of "foo = foo$$bar", the makefile needs to contain "foo := foo$$bar".  This will work with both the old and new versions of GNU make.

The first regression (dollar.test) is due to the know backwards-incompatibility (documented in the NEWS file).

The second and the third regressions (yacc4.test and yacc6.test) are due to the same bug that I re-entered with a minimal example as bug #12267. This bug has been fixed.