AM_CPPFLAGS vs. [lib]_CPPFLAGS

[Bill Moseley]

I'm making an convenience library like the following.  Note the *_CPPFLAGS

noinst_LTLIBRARIES = libswishindex.la
libswishindex_la_LIBADD =  expat/libswexpat.la $(LIBXML2_OBJS) 
replace/libreplace.la
libswishindex_la_LDFLAGS = $(LIBXML2_LIB) $(Z_LIBS) $(PCRE_LIBS)
libswishindex_la_CPPFLAGS = $(LIBXML2_CFLAGS) $(Z_CFLAGS) $(PCRE_CFLAGS) 
-Ireplace
libswishindex_la_DEPENDENCIES = $(libswishindex_la_LIBADD)
EXTRA_libswishindex_la_SOURCES = parser.c parser.h


In the same Makefile.am I'm building two other libraries and a binary from
those libraries.

I was finding that I was repeating the *_CPPFLAGS for each library so I
thought it would clean things up to use a global AM_CPPFLAGS instead and
not use the program or library specific CPPFLAGS

But if I simply rename libswishindex_la_CPPFLAGS to AM_CPPLFAGS then I
get:

make[3]: *** No rule to make target `libswishindex_la-parser.lo', needed  by 
`libswishindex.la'.  Stop.

"parser.lo" is conditionally added in the configure script.

    LIBXML2_OBJS="libswishindex_la-parser.lo"
    AC_SUBST(LIBXML2_OBJS)

Here's a comparison of the gcc line using the two *_CPPFLAGS:

This one is using libswishindex_la_CPPFLAGS and works fine:

gcc [...] -c ../../swish-e/src/docprop_write.c 
-Wp,-MD,.deps/libswishindex_la-docprop_write.TPlo -o 
libswishindex_la-docprop_write.o >/dev/null 2>&1

 
This one is using AM_CPPFLAGS and blows up

gcc [...] -c ../../swish-e/src/docprop_write.c -Wp,-MD,.deps/docprop_write.TPlo 
-o docprop_write.o >/dev/null 2>&1

I know (from guessing) I can fix by changing my configure.in to use:

 LIBXML2_OBJS="parser.lo"

But I don't understand why.  Is this expected behavior?



-- 
Bill Moseley address@hidden