Re: [Bug-gnulib] Re: modules/{sysexits,poll}: syntax nits

[Bruno Haible]

Simon Josefsson wrote:
> I'm not sure I understand what difference using one over the other
> would have.

The change recommended by Alexandre is a no-op. As I understand it,
the benefit of using $(VAR) over @VAR@ in Makefiles is that in the
bigger picture of the GNU build system (= autoconf + automake + libtoolize
+ gettextize) things get simpler because the user doesn't need to know
whether a certain feature comes from automake or autoconf. In other words,
it reduces the learning curve of beginners.

However, not in all cases can @VAR@ be replaced with $(VAR). Here are three
cases:

1) Synthethized variable names, e.g.
   Dependencies that depends on an autoconf result.

FOO_DEPS = $(address@hidden@)
FOO_DEPS_yes = some files
FOO_DEPS_no = some other files
foo$(EXEEXT) : $(FOO_DEPS)

2) Variables which expand to Makefile rules or dependencies. Example
from gettext:

@SET_RELOCATABLE@

This line expands to empty or to

RELOCATABLE_LDFLAGS = "$reloc_ldflags" "$(host)" "$(RELOCATABLE_LIBRARY_PATH)"

or to

INSTALL_PROGRAM_ENV = RELOC_LIBRARY_PATH_VAR="$shlibpath_var" 
RELOC_LIBRARY_PATH_VALUE="$(RELOCATABLE_LIBRARY_PATH)" RELOC_PREFIX="$(prefix)" 
RELOC_COMPILE_COMMAND="$(CC) $(CPPFLAGS) $(CFLAGS) $(LDFLAGS)" 
RELOC_SRCDIR="$(RELOCATABLE_SRC_DIR)" RELOC_BUILDDIR="$(RELOCATABLE_BUILD_DIR)" 
RELOC_CONFIG_H_DIR="$(RELOCATABLE_CONFIG_H_DIR)" 
RELOC_INSTALL_PROG="$INSTALL_PROGRAM"

depending on the platform.

3) Variable definitions which override those from automake. Example:

MAKEINFO = env LANG= LC_MESSAGES= LC_ALL= LANGUAGE= @MAKEINFO@

(This one prevents makeinfo from generating .info files with German words
near the beginning, in my environment.)

In none of these case can you replace @...@ with $(...).


Bruno