Use system provided libsignal-protocol-c by default

You can still compile in tree by using --with-libsignal-in-tree flag

.travis.yml

@@ -6,7 +6,7 @@ env:
 before_install:
   - export USE_CCACHE=1
   - sudo apt-get update
-  - sudo apt-get install -y cmake valac libgee-0.8-dev libsqlite3-dev libgtk-3-dev libnotify-dev libgpgme-dev libsoup2.4-dev libgcrypt20-dev libqrencode-dev
+  - sudo apt-get install -y cmake valac libgee-0.8-dev libsqlite3-dev libgtk-3-dev libnotify-dev libgpgme-dev libsoup2.4-dev libgcrypt20-dev libqrencode-dev libsignal-protocol-c-dev
 install:
   - ./configure --with-tests $CONFIGURE_FLAGS
   - make

cmake/FindSignalProtocol.cmake

@@ -1,10 +1,11 @@
 include(PkgConfigWithFallback)
 find_pkg_config_with_fallback(SignalProtocol
-    PKG_CONFIG_NAME signal-protocol-c
+    PKG_CONFIG_NAME libsignal-protocol-c
     LIB_NAMES signal-protocol-c
     INCLUDE_NAMES signal/signal_protocol.h
 )
 
 include(FindPackageHandleStandardArgs)
 find_package_handle_standard_args(SignalProtocol
-    REQUIRED_VARS SignalProtocol_LIBRARY)
+    REQUIRED_VARS SignalProtocol_LIBRARY
+    VERSION_VAR SignalProtocol_VERSION)

configure

@@ -1,7 +1,7 @@
 #!/bin/sh
 
 OPTS=`getopt -o "h" --long \
-help,fetch-only,no-debug,disable-fast-vapi,with-tests,release,\
+help,fetch-only,no-debug,disable-fast-vapi,with-tests,release,with-libsignal-in-tree,\
 enable-plugin:,disable-plugin:,\
 prefix:,program-prefix:,exec-prefix:,lib-suffix:,\
 bindir:,libdir:,includedir:,datadir:,\
@@ -17,6 +17,7 @@ eval set -- "$OPTS"
 PREFIX=${PREFIX:-/usr/local}
 ENABLED_PLUGINS=
 DISABLED_PLUGINS=
+BUILD_LIBSIGNAL_IN_TREE=
 BUILD_TESTS=
 BUILD_TYPE=Debug
 DISABLE_FAST_VAPI=
@@ -52,9 +53,11 @@ Configuration:
                              clean builds, but faster when doing incremental
                              builds (during development).
   --fetch-only               Only fetch the files required to run ./configure
-                             without network access later and exit
+                             without network access later and exit.
   --no-debug                 Build without debug symbols
   --release                  Configure to build an optimized release version
+  --with-libsignal-in-tree   Build libsignal-protocol-c in tree and link it
+                             statically.
   --with-tests               Also build tests.
 
 Plugin configuration:
@@ -110,6 +113,7 @@ while true; do
         --valac ) VALA_EXECUTABLE="$2"; shift; shift ;;
         --valac-flags ) VALAC_FLAGS="$2"; shift; shift ;;
         --lib-suffix ) LIB_SUFFIX="$2"; shift; shift ;;
+        --with-libsignal-in-tree ) BUILD_LIBSIGNAL_IN_TREE=yes; shift ;;
         --disable-fast-vapi ) DISABLE_FAST_VAPI=yes; shift ;;
         --no-debug ) NO_DEBUG=yes; shift ;;
         --fetch-only ) FETCH_ONLY=yes; shift ;;
@@ -141,6 +145,7 @@ while true; do
     esac
 done
 
+if [ "$BUILD_LIBSIGNAL_IN_TREE" = "yes" ] || [ "$FETCH_ONLY" = "yes" ]; then
     if [ -d ".git" ]; then
         git submodule update --init 2>/dev/null
     else
@@ -180,6 +185,7 @@ else
             tmp=$i
         done
     fi
+fi
 
 if [ "$FETCH_ONLY" = "yes" ]; then exit 0; fi
 
@@ -256,6 +262,7 @@ cmake -G "$cmake_type" \
     -DENABLED_PLUGINS="$ENABLED_PLUGINS" \
     -DDISABLED_PLUGINS="$DISABLED_PLUGINS" \
     -DBUILD_TESTS="$BUILD_TESTS" \
+    -DBUILD_LIBSIGNAL_IN_TREE="$BUILD_LIBSIGNAL_IN_TREE" \
     -DVALA_EXECUTABLE="$VALAC" \
     -DCMAKE_VALA_FLAGS="$VALACFLAGS" \
     -DDISABLE_FAST_VAPI="$DISABLE_FAST_VAPI" \

plugins/signal-protocol/CMakeLists.txt

@@ -28,8 +28,11 @@ GENERATE_HEADER
 set(C_HEADERS_SRC "")
 set(C_HEADERS_TARGET "")
 
-if((SHARED_SIGNAL_PROTOCOL) OR ($ENV{SHARED_SIGNAL_PROTOCOL}))
-    find_package(SignalProtocol REQUIRED)
+if(NOT BUILD_LIBSIGNAL_IN_TREE)
+    # libsignal-protocol-c has a history of breaking compatibility on the patch level
+    # we'll have to check compatibility for every new release
+    # distro maintainers may update this dependency after compatibility tests
+    find_package(SignalProtocol 2.3.2 EXACT REQUIRED)
 else()
     add_subdirectory(libsignal-protocol-c EXCLUDE_FROM_ALL)
     set_property(TARGET curve25519 PROPERTY POSITION_INDEPENDENT_CODE ON)