Preserve CFLAGS & CXXFLAGS for the configure user

The Automake manual makes it clear that certain user variables such as
CC, CFLAGS, CXXFLAGS, CPPFLAGS, and so on are to be preserved for the
user running configure.  This patch cleans up such assignments and
assures that PTHREAD_CFLAGS and so forth are applied to those targets
that require it.

ars/Makefile.am

@@ -1,3 +1,4 @@
+AM_CFLAGS = @AM_CFLAGS@ $(PTHREAD_CFLAGS)
 
 pkglib_LTLIBRARIES = hamlib-ars.la
 hamlib_ars_la_SOURCES = ars.c

configure.ac

@@ -94,9 +94,10 @@ PKG_PROG_PKG_CONFIG
 AC_C_INLINE
 
 dnl Set warnings for compilation
+dnl CFLAGS and CXXFLAGS are reserved for user, so set their AM_* counterparts.
 # macros/ax_cflags_warn_all.m4
-AX_CFLAGS_WARN_ALL
-AX_CXXFLAGS_WARN_ALL
+AX_CFLAGS_WARN_ALL([AM_CFLAGS])
+AX_CXXFLAGS_WARN_ALL([AM_CXXFLAGS])
 
 dnl Automake macro for rigmem compilation
 AM_PROG_CC_C_O
@@ -130,12 +131,11 @@ dnl Check for Mingw (Win32 Sleep) support
 # macros/gr_pwin32.m4
 GR_PWIN32
 
+dnl If pthread support is found, this macro defines HAVE_PTHREAD and
+dnl AC_SUBST's PTHREAD_LIBS, PTHREAD_CFLAGS, and PTHREAD_CC making those
+dnl variables available in Makefiles.
 # macros/ax_pthread.m4
 AX_PTHREAD
-AS_IF([test x"$ax_pthread_ok" = "xyes"], [
-      CFLAGS="${CFLAGS} ${PTHREAD_CFLAGS}"
-      CXXFLAGS="${CXXFLAGS} ${PTHREAD_CFLAGS}"
-])
 
 AC_SYS_POSIX_TERMIOS()
 
@@ -283,8 +283,8 @@ AS_CASE(["$host_os"],
     [darwin* | rhapsody*], [
         # Trick from http://fink.sourceforge.net/doc/porting/
         # TODO: check the compiler actually does support these options
-        CFLAGS="${CFLAGS} -no-cpp-precomp"
-        CXXFLAGS="${CXXFLAGS} -no-cpp-precomp"
+        AM_CFLAGS="${AM_CFLAGS} -no-cpp-precomp"
+        AM_CXXFLAGS="${AM_CXXFLAGS} -no-cpp-precomp"
 
         # Tell the OS X linker to allocate enough space inside the
         # libhamlib.X.dylib shared object for install_name_tool(1) to
@@ -613,12 +613,12 @@ AM_CONDITIONAL([ENABLE_CXX], [test x"${cf_with_cxx}" = "xyes"])
 AM_CONDITIONAL([HAVE_USRP], [test x"${cf_with_usrp}" = "xyes"])
 
 
+dnl Defines LIBUSB_CFLAGS and LIBUSB_LIBS as precious variables
+dnl so they appear in all Makefiles.
+# macros/pkg.m4
 PKG_CHECK_MODULES([LIBUSB], [libusb >= 0.1], [],
                   [AC_MSG_WARN([libusb pkg-config not found, USB backends will be disabled])])
 
-CFLAGS="${CFLAGS} ${LIBUSB_CFLAGS}"
-CXXFLAGS="${CXXFLAGS} ${LIBUSB_CFLAGS}"
-
 AC_CHECK_HEADERS([usb.h])
 AC_MSG_CHECKING([whether to build USB backends])
 
@@ -668,7 +668,11 @@ done
 AC_SUBST([ROT_BACKEND_LIST])
 AC_SUBST([ROT_BACKENDLNK])
 AC_SUBST([ROT_BACKENDEPS])
+
+dnl Output accumulated flags to the Makefile files.
 AC_SUBST([AM_CPPFLAGS])
+AC_SUBST([AM_CFLAGS])
+AC_SUBST([AM_CXXFLAGS])
 
 
 AC_CONFIG_FILES([Makefile
@@ -732,9 +736,9 @@ echo \
  ${PACKAGE_NAME} Version ${PACKAGE_VERSION} configuration:
 
  Prefix         ${prefix}
- C Compiler     ${CC} ${CFLAGS} ${CPPFLAGS}
- C++ Compiler   ${CXX} ${CXXFLAGS} ${CPPFLAGS}
-
+ Preprocessor   ${CPP} ${CPPFLAGS}
+ C Compiler     ${CC} ${CFLAGS}
+ C++ Compiler   ${CXX} ${CXXFLAGS}
 
  Package features:
     With C++ binding                ${cf_with_cxx_binding}

gnuradio/Makefile.am

@@ -1,6 +1,6 @@
 
-AM_CFLAGS = @GNURADIO_CFLAGS@ @PTHREAD_CFLAGS@
-AM_CXXFLAGS = $(AM_CFLAGS)
+AM_CFLAGS = @AM_CFLAGS@ @GNURADIO_CFLAGS@ $(PTHREAD_CFLAGS)
+AM_CXXFLAGS = @AM_CXXFLAGS@ @GNURADIO_CFLAGS@ $(PTHREAD_CFLAGS)
 
 pkglib_LTLIBRARIES = hamlib-gnuradio.la
 hamlib_gnuradio_la_SOURCES = mc4020.c graudio.c gr.c gnuradio.cc
@@ -8,7 +8,7 @@ hamlib_gnuradio_la_SOURCES = mc4020.c graudio.c gr.c gnuradio.cc
 hamlib_gnuradio_la_LDFLAGS = -no-undefined -module -avoid-version
 
 # requires libgnuradio, libfftw and c++
-hamlib_gnuradio_la_LIBADD = $(top_builddir)/src/libhamlib.la @GNURADIO_LIBS@ -lstdc++ @PTHREAD_LIBS@
+hamlib_gnuradio_la_LIBADD = $(top_builddir)/src/libhamlib.la @GNURADIO_LIBS@ -lstdc++ $(PTHREAD_LIBS)
 
 noinst_HEADERS = gnuradio.h gr_priv.h demod.h nfm.h am.h ssb.h wfm.h HrAGC.h
 

kit/Makefile.am

@@ -1,11 +1,12 @@
-AM_CFLAGS = @LIBUSB_CFLAGS@
+AM_CFLAGS = @AM_CFLAGS@ $(LIBUSB_CFLAGS)
 
 # FIXME: compile usrp only if CXX available
 KITSRCLIST = elektor304.c drt1.c dwt.c usrp.c elektor507.c \
 	     dds60.c miniVNA.c si570avrusb.c funcube.c fifisdr.c hiqsdr.c
 
 if HAVE_USRP
-    AM_CXXFLAGS = @USRP_CFLAGS@
+    # Append to the already defined AM_CXXFLAGS that exists outside the conditional.
+    AM_CXXFLAGS += @USRP_CFLAGS@
     KITSRCLIST += usrp_impl.cc
     hamlib_kit_la_LINK = $(CXXLINK) $(hamlib_kit_la_LDFLAGS)
 else

tests/Makefile.am

@@ -29,6 +29,8 @@ LDADD = $(top_builddir)/src/libhamlib.la $(top_builddir)/lib/libmisc.la
 DEPENDENCIES = $(top_builddir)/src/libhamlib.la
 
 rigmem_CFLAGS = $(AM_CFLAGS) @LIBXML2_CFLAGS@
+rigctld_CFLAGS = $(AM_CFLAGS) $(PTHREAD_CFLAGS)
+rotctld_CFLAGS = $(AM_CFLAGS) $(PTHREAD_CFLAGS)
 
 ## Linker options
 listrigs_LDFLAGS = @BACKENDLNK@