build: Extract the libbitcoinkernel library

I strongly recommend reviewing with the following git-diff flags:
  --patience --color-moved=dimmed-zebra

Extract out a libbitcoinkernel library linking in all files necessary
for using our consensus engine as-is. Link bitcoin-chainstate against
it.

See previous commit "build: Add example bitcoin-chainstate executable"
for more context.

We explicitly specify -fvisibility=default, which effectively overrides
the effects of --enable-reduced-exports since libbitcoinkernel requires
default symbol visibility

When compiling for mingw-w64, specify -static in both:

- ..._la_CXXFLAGS so that libtool will avoid building two versions of
  each object (one PIC, one non-PIC). We just need the one that is
  suitable for static linking.
- ..._la_LDFLAGS so that libtool will create a static library.

If we don't specify this, then libtool will prefer the non-static PIC
version of the object, which is built with -DDLL_EXPORT -DPIC for
mingw-w64 targets. This can cause symbol resolution problems when we
link this library against an executable that does specify -all-static,
since that will be built without the -DDLL_EXPORT flag.

Unfortunately, this means that for mingw-w64 we can only build a static
version of the library for now. This will be fixed.

However, on other targets, the shared library creation works fine.

-----

Note to users: You need to either specify:

  --enable-experimental-util-chainstate

or,

  --with-experimental-kernel-lib

To build the libbitcionkernel library. See the configure help for more
details.

build shared libbitcoinkernel where we can

1 files changed, 15 insertions, 1 deletions

diff --git a/configure.ac b/configure.ac
index ee5f0e8d06..b3a5e2be8d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -663,6 +663,12 @@ AC_ARG_WITH([libs],
   [build_bitcoin_libs=$withval],
   [build_bitcoin_libs=yes])
 
+AC_ARG_WITH([experimental-kernel-lib],
+  [AS_HELP_STRING([--with-experimental-kernel-lib],
+  [build experimental bitcoinkernel library (default is to build if we're building libraries and the experimental build-chainstate executable)])],
+  [build_experimental_kernel_lib=$withval],
+  [build_experimental_kernel_lib=auto])
+
 AC_ARG_WITH([daemon],
   [AS_HELP_STRING([--with-daemon],
   [build bitcoind daemon (default=yes)])],
@@ -1657,15 +1663,23 @@ AM_CONDITIONAL([BUILD_BITCOIN_UTIL], [test $build_bitcoin_util = "yes"])
 AC_MSG_RESULT($build_bitcoin_util)
 
 AC_MSG_CHECKING([whether to build experimental bitcoin-chainstate])
-AM_CONDITIONAL([BUILD_BITCOIN_CHAINSTATE], [test $build_bitcoin_chainstate = "yes"])
+if test "$build_experimental_kernel_lib" = "no"; then
+AC_MSG_ERROR([experimental bitcoin-chainstate cannot be built without the experimental bitcoinkernel library. Use --with-experimental-kernel-lib]);
+else
+  AM_CONDITIONAL([BUILD_BITCOIN_CHAINSTATE], [test $build_bitcoin_chainstate = "yes"])
+fi
 AC_MSG_RESULT($build_bitcoin_chainstate)
 
 AC_MSG_CHECKING([whether to build libraries])
 AM_CONDITIONAL([BUILD_BITCOIN_LIBS], [test $build_bitcoin_libs = "yes"])
+
 if test "$build_bitcoin_libs" = "yes"; then
   AC_DEFINE([HAVE_CONSENSUS_LIB], [1], [Define this symbol if the consensus lib has been built])
   AC_CONFIG_FILES([libbitcoinconsensus.pc:libbitcoinconsensus.pc.in])
 fi
+
+AM_CONDITIONAL([BUILD_BITCOIN_KERNEL_LIB], [test "$build_experimental_kernel_lib" != "no" && ( test "$build_experimental_kernel_lib" = "yes" || test "$build_bitcoin_chainstate" = "yes" )])
+
 AC_MSG_RESULT($build_bitcoin_libs)
 
 AC_LANG_POP