On Thu, Dec 01, 2011 at 09:08:27AM +0100, Arnaud Charlet wrote:
> > := assigned variable gets evaluated right away, including the case when
> > host doesn't have any Ada compiler installed. In that case we remove ada
> > from enabled languages, but still RTS_DIR is sometimes computed.
>
> Can you elaborate here? When is RTS_DIR computed if Ada is not enabled?
> That seems surprising to me, so I'd like to understand more before OKing
> this patch.
As written in the PR, even if you on say x86_64-linux
../configure --enable-languages=c --target=i686-pc-linux-gnu
you end up with:
CONFIG_LANGUAGES = c++ lto
LANGUAGES = c gcov$(exeext) gcov-dump$(exeext) $(CONFIG_LANGUAGES)
...
LANG_MAKEFRAGS = $(srcdir)/ada/gcc-interface/Make-lang.in
$(srcdir)/cp/Make-lang.in $(srcdir)/fortran/Make-lang.in
$(srcdir)/go/Make-lang.in $(srcdir)/java/Make-lang.in
$(srcdir)/lto/Make-lang.in $(srcdir)/objc/Make-lang.in
$(srcdir)/objcp/Make-lang.in
...
# per-language makefile fragments
ifneq ($(LANG_MAKEFRAGS),)
include $(LANG_MAKEFRAGS)
endif
in gcc/Makefile. When Ada isn't installed on the host, you end
up with something like:
...
checking whether g++ accepts -g... yes
checking for alloca... yes
checking for x86_64-unknown-linux-gnu-gnatbind... no
checking for x86_64-unknown-linux-gnu-gnatmake... no
checking whether compiler driver understands Ada... no
checking how to run the C preprocessor... yes
gcc -E
checking for ANSI C header files... (cached) yes
...
config.status: creating ada/gcc-interface/Makefile
config.status: creating ada/Makefile
config.status: creating auto-host.h
config.status: executing default commands
/bin/sh: gnatls: command not found
make[2]: Entering directory `/usr/src/gcc/obj3/gcc'
/bin/sh ../../gcc/../mkinstalldirs po
/bin/sh ../../gcc/../mkinstalldirs po
/bin/sh ../../gcc/../mkinstalldirs po
...
in the output. That is because ada/gcc-interface/Make-lang.in is sourced,
even when no goals from it are actually made. But already mere sourcing
of that makefile results in
ifeq ($(build), $(host))
ifeq ($(host), $(target))
...
else
...
RTS_DIR:=$(strip $(subst \,/,$(shell gnatls -v | grep adalib )))
...
endif
else
...
endif
$(build) and $(host) is equal here, $(host) and $(target) aren't equal
and thus RTS_DIR variable is initialized from the command, irrespective
from host GNAT not being detected or present.
By changing that variable to deferred:
RTS_DIR=$(strip $(subst \,/,$(shell gnatls -v | grep adalib )))
no command is run when the makefile fragment is sourced,
instead the command is executed when the vars are actually used:
ADA_TOOLS_FLAGS_TO_PASS=\
CC="$(CC)" \
$(COMMON_FLAGS_TO_PASS) $(ADA_FLAGS_TO_PASS) \
ADA_INCLUDES="-I$(RTS_DIR)../adainclude -I$(RTS_DIR)" \
GNATMAKE="gnatmake" \
GNATBIND="gnatbind" \
GNATLINK="gnatlink" \
LIBGNAT=""
...
gnattools: $(GCC_PARTS) $(CONFIG_H) prefix.o force
$(MAKE) -C ada $(ADA_TOOLS_FLAGS_TO_PASS) gnattools1
$(MAKE) -C ada $(ADA_TOOLS_FLAGS_TO_PASS) gnattools2
For gnattools target, this means that gnatls is with the patch
invoked 4 times, twice per gnattools1 subcommand and twice
per gnattools2 subcommand, but it is evaluated before spawning
the submake (i.e. we don't run gnatls per command line).
Jakub
