Support building rpm without Berkeley DB, simplify the configuration

Replace the --with-external-db switch with the following simple logic:
if internal copy of BDB is detected, use it, otherwise look for an
external one. By default BDB is still required, but it's now possible
to build without it by using --disable-bdb argument to configure.
If no database is built in, we'll segfault for now, to be dealt with
in coming commits.

This is a rather historical moment, BTW.

INSTALL

@@ -67,12 +67,12 @@ distinct advantages and disadvantages:
    hand, major BDB upgrades can be disruptive, especially if
    the on-disk format changes somehow. 
 
-   To use this method, simply pass in --with-external-db to ./configure
-   script. If the system BDB is installed outside compiler + linker default
+   This method is the default if no "db" link exists in the top directory.
+   If the system BDB is installed outside compiler + linker default
    paths, you can use CPPFLAGS and LDFLAGS to tell configure where to look,
    for example:
 
-   $ ./configure --with-external-db CPPFLAGS=-I/usr/include/db45
+   $ ./configure CPPFLAGS=-I/usr/include/db45
 
 Minimal instructions for building BDB are 
     cd build_unix 

Makefile.am

@@ -2,7 +2,7 @@
 
 ACLOCAL_AMFLAGS = -I m4
 
-DISTCHECK_CONFIGURE_FLAGS = --with-external-db --enable-python
+DISTCHECK_CONFIGURE_FLAGS = --enable-python
 
 include $(top_srcdir)/rpm.am
 AM_CFLAGS = @RPMCFLAGS@

configure.ac

@@ -498,63 +498,47 @@ AM_CONDITIONAL(LIBDW,[test "$WITH_LIBDW" = yes])
 AM_CONDITIONAL(HAVE_LIBDW_STRTAB,[test "$HAVE_LIBDW_STRTAB" = yes])
 
 #=================
-# Process --with/without-external-db
-AC_ARG_WITH(external_db, [AS_HELP_STRING([--with-external-db],[build against an external Berkeley db])],
-[case "$with_external_db" in
-yes|no) ;;
-*) AC_MSG_ERROR([invalid argument to --with-external-db]) ;;
-esac],
-[with_external_db=maybe])
-
-case "$with_external_db" in
-yes )
-  AC_CHECK_HEADERS([db.h],[
-    AC_PREPROC_IFELSE([
-      AC_LANG_SOURCE([
-	#include <db.h>
-	#if ((DB_VERSION_MAJOR < 4) || (DB_VERSION_MAJOR == 4 && DB_VERSION_MINOR < 5))
-	#error Berkeley DB too old
-	#endif
-      ])
-    ],[ WITH_DB_LIB=-ldb ], 
-      [ AC_MSG_ERROR([Berkeley DB version >= 4.5 required])
-    ])
-  ],[
-    AC_MSG_ERROR([missing required header db.h])
-  ])
-  ;;
-no|maybe )
-  # Try internal database first, then fall back to external
-  # unless --without-external-db (no) was explicitly given.
+# Check for BDB support
+AC_ARG_ENABLE([bdb],
+              [AS_HELP_STRING([--enable-bdb=@<:@yes/no/auto@:>@],
+                              [build with Berkeley DB rpm database format support (default=yes)])],
+              [enable_bdb="$enableval"],
+              [enable_bdb=yes])
+
+AS_IF([test "x$enable_bdb" != "xno"], [
   if [ test -x db/dist/configure ]; then
-    with_external_db=no
+    have_bdb="internal"
   else
-    case "$with_external_db" in
-    maybe)
-      AC_CHECK_HEADERS([db.h],[
-        AC_PREPROC_IFELSE([
-          AC_LANG_SOURCE([
-	    #include <db.h>
-	    #if ((DB_VERSION_MAJOR < 4) || (DB_VERSION_MAJOR == 4 && DB_VERSION_MINOR < 5))
-	    #error Berkeley DB too old
-	    #endif
-          ])
-        ],[ WITH_DB_LIB=-ldb ],
-          [ AC_MSG_ERROR([Berkeley DB version >= 4.5 required])
+    have_bdb="no"
+    AC_CHECK_HEADERS([db.h],[
+      AC_PREPROC_IFELSE([
+        AC_LANG_SOURCE([
+	  #include <db.h>
+	  #if ((DB_VERSION_MAJOR < 4) || (DB_VERSION_MAJOR == 4 && DB_VERSION_MINOR < 5))
+	  #error Berkeley DB too old
+	  #endif
         ])
-      ],[
-        AC_MSG_ERROR([missing required header db.h])
-      ])
-    ;;
-    no)
-      AC_MSG_ERROR([internal Berkeley DB directory not present, see INSTALL])
-    ;;
-    esac
+      ],[ have_bdb="yes" ])
+    ])
   fi
-  ;;
-esac
+  AC_MSG_CHECKING(for Berkeley DB >= 4.5)
+  AC_MSG_RESULT($have_bdb)
+  AS_IF([test "x$enable_bdb" = "xyes"], [
+    if test "x$have_bdb" = "xno"; then
+      AC_MSG_ERROR([--enable-bdb specified, but not available])
+    fi
+    AC_DEFINE([WITH_BDB], [1], [Define if BDB is available])
+    WITH_DB_LIB=-ldb
+    AC_SUBST([WITH_DB_LIB])
+  ])
+])
+
+AM_CONDITIONAL([BDB], [test "x$have_bdb" != "xno"])
+AM_CONDITIONAL([WITH_INTERNAL_DB],[test "x$have_bdb" = "xinternal"])
+if test "x$have_bdb" = "xinternal"; then
+    AC_CONFIG_SUBDIRS(db3)
+fi
 
-AC_SUBST([WITH_DB_LIB])
 
 #=================
 # Process --enable-ndb
@@ -1052,11 +1036,6 @@ AC_SUBST(RPMCONFIGDIR)
 
 AC_SUBST(OBJDUMP)
 
-if test "$with_external_db" = no; then
-    AC_CONFIG_SUBDIRS(db3)
-fi
-
-AM_CONDITIONAL([WITH_INTERNAL_DB],[test "$with_external_db" = no])
 AM_CONDITIONAL([DOXYGEN],[test "$DOXYGEN" != no])
 AM_CONDITIONAL([HACKINGDOCS],[test "$with_hackingdocs" = yes])
 

lib/Makefile.am

@@ -24,7 +24,7 @@ EXTRA_PROGRAMS =
 
 usrlib_LTLIBRARIES = librpm.la
 librpm_la_SOURCES = \
-	backend/db3.c backend/dbi.c backend/dbi.h \
+	backend/dbi.c backend/dbi.h \
 	backend/dbiset.c backend/dbiset.h \
 	headerutil.c header.c headerfmt.c header_internal.h \
 	rpmdb.c rpmdb_internal.h \
@@ -59,11 +59,14 @@ librpm_la_LIBADD += @LUA_LIBS@
 librpm_la_SOURCES += rpmliblua.c rpmliblua.h
 endif
 
+if BDB
 if WITH_INTERNAL_DB
+librpm_la_SOURCES += backend/db3.c
 librpm_la_LIBADD += $(libdb_la)
 else
 librpm_la_LIBADD += @WITH_DB_LIB@
 endif
+endif
 
 if NDB
 librpm_la_SOURCES += \

lib/backend/dbi.c

@@ -49,13 +49,15 @@ dbDetectBackend(rpmdb rdb)
 	rdb->db_ops = &ndb_dbops;
     } else
 #endif
+#if defined(WITH_BDB)
     {
 	rdb->db_ops = &db3_dbops;
 	if (*db_backend == '\0') {
 	    free(db_backend);
 	    db_backend = xstrdup("bdb");
 	}
     }
+#endif
 
 #if defined(WITH_LMDB)
     path = rstrscat(NULL, dbhome, "/data.mdb", NULL);
@@ -75,12 +77,14 @@ dbDetectBackend(rpmdb rdb)
     free(path);
 #endif
 
+#if defined(WITH_BDB)
     path = rstrscat(NULL, dbhome, "/Packages", NULL);
     if (access(path, F_OK) == 0 && rdb->db_ops != &db3_dbops) {
 	rdb->db_ops = &db3_dbops;
 	rpmlog(RPMLOG_WARNING, _("Found BDB Packages database while attempting %s backend: using bdb backend.\n"), db_backend);
     }
     free(path);
+#endif
 
     if (db_backend)
 	free(db_backend);

lib/backend/dbi.h

@@ -262,8 +262,10 @@ struct rpmdbOps_s {
     const void * (*idxdbKey)(dbiIndex dbi, dbiCursor dbc, unsigned int *keylen);
 };
 
+#if defined(WITH_BDB)
 RPM_GNUC_INTERNAL
 extern struct rpmdbOps_s db3_dbops;
+#endif
 
 #ifdef ENABLE_NDB
 RPM_GNUC_INTERNAL