Hello automakers. The current automake implementation of variable-appending operator `+=' tries to be smart w.r.t. comments in the values; for example:
$ cat configure.ac AC_INIT(x,0) AM_INIT_AUTOMAKE AC_CONFIG_FILES(Makefile) AC_OUTPUT $ cat Makefile.am foo1 = bar # comment 1 foo1 += baz # comment 2 foo2 = bar foo2 += baz # comment 3 foo3 = bar baz # comment 4 results in: $ aclocal && automake --foreign --add-missing configure.ac:2: installing `./install-sh' configure.ac:2: installing `./missing' $ grep '^foo[0-9] *=' Makefile.in foo1 = bar baz # comment 2 foo2 = bar baz # comment 3 foo3 = bar baz # comment 4 which is admittedly better than having something bogus like: $ cat Makefile.am foo = bar # comment foo += baz $ aclocal && automake ... $ grep '^foo *=' Makefile.in foo = bar # comment baz However, the code in automake is apparently not smart enough to detect that someone might be trying to put a *literal* `#' character in a variable extended with `+=': $ cat configure.ac AC_INIT(x,0) AM_INIT_AUTOMAKE AC_CONFIG_FILES(Makefile) AC_OUTPUT $ cat Makefile.am CDEFS = -D'FOO_STRING="\#\#foo\#\#"' CDEFS += -DBAR $ aclocal && automake --foreign --add-missing configure.ac:2: installing `./install-sh' configure.ac:2: installing `./missing' $ grep '^CDEFS *=' Makefile.in CDEFS = -D'FOO_STRING="\ -DBAR Now, while the above use of -D'FOO_STRING="\#\#foo\#\#"' in a variable definition is certainly bound to produce code unportable to some make implementations, the right thing for automake to do is either to assume the user knows what he's doing (maybe he's not interested into portability to those make implementations), or to warn about the unportable usage (if `-Wportability' is enabled, obviously). Silently mangling the value of the resulting value of $(DEFS) is *not* an acceptale behaviour IMHO, but unfortunately, that's exactly what automake currently does (as seen above). Tangentially, note that the definition: CDEFS = -D'FOO_STRING="\#\#foo\#\#"' actually works with at least GNU make, modern FreeBSD make, and modern NetBSD make: $ cat Makefile CDEFS = -D'FOO_STRING="\#\#foo\#\#"' all:; @echo $(CDEFS) $ make # is either GNU, FreeBSD or NetBSD make -DFOO_STRING="##foo##" and "sorta" works with Solaris 10 make: $ /usr/xpg4/bin/make -DFOO_STRING="\#\#foo\#\#" $ /usr/ccs/bin/make -DFOO_STRING="\#\#foo\#\#" Regards, Stefano
