README.Linux: add build instructions for V8 5.6, closes #269

README.Linux.md

@@ -10,6 +10,11 @@ years ago, since Node.js requires such an old version.
 This means that you usually need to compile v8 on your own before
 you can start to compile & install v8js itself.
 
+It is recommended to install the V8 version for V8Js off your system's
+load path, so it doesn't interfere with the V8 library shipped with your
+system's distribution.
+
+
 Snapshots
 ---------
 
@@ -24,10 +29,47 @@ so there's no need to handle them specially.
 Besides there are external snapshots (which are enabled unless configured
 otherwise).  If V8 is compiled with these, then V8Js needs to provide two
 "binary blobs" to V8, named `natives_blob.bin` and `snapshot_blob.bin`.
-In that case copy those two files to `/usr/share/v8/...`.
+In that case copy those two files to the same directory `libv8.so` was
+installed to.
 
-Compile latest V8
+
------------------
+Compile V8 5.6 and newer (using GN)
+-----------------------------------
+
+```
+# Install required dependencies
+sudo apt-get install build-essential git python libglib2.0-dev
+
+cd /tmp
+
+# Install depot_tools first (needed for source checkout)
+git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
+export PATH=`pwd`/depot_tools:"$PATH"
+
+# Download v8
+fetch v8
+cd v8
+
+# (optional) If you'd like to build a certain version:
+git checkout 5.6.326.12
+gclient sync
+
+# Setup GN
+tools/dev/v8gen.py -vv x64.release
+echo is_component_build = true >> out.gn/x64.release/args.gn
+
+# Build
+ninja -C out.gn/x64.release/
+
+# Install to /opt/v8/
+sudo mkdir -p /opt/v8/{lib,include}
+sudo cp out.gn/x64.release/lib*.so out.gn/x64.release/*_blob.bin /opt/v8/lib/
+sudo cp -R include/* /opt/v8/include/
+```
+
+
+Compile V8 versions 5.5 and older (using Gyp)
+---------------------------------------------
 
 
 ```
@@ -60,25 +102,21 @@ export GYPFLAGS="${GYPFLAGS} -Dlinux_use_bundled_gold=0"
 # Compile V8 (using up to 8 CPU cores, requires a lot of RAM, adapt as needed)
 make native library=shared snapshot=on -j8
 
-# Install to /usr
+# Install to /opt/v8
-sudo mkdir -p /usr/lib /usr/include
+sudo mkdir -p /opt/v8/{lib,include}
-sudo cp out/native/lib.target/lib*.so /usr/lib/
+sudo cp out/native/lib.target/lib*.so /opt/v8/lib/
-sudo cp -R include/* /usr/include
+sudo cp -R include/* /opt/v8/include
 
 # Fix libv8.so's RUNPATH header
-sudo chrpath -r '$ORIGIN' /usr/lib/libv8.so
+sudo chrpath -r '$ORIGIN' /opt/v8/lib/libv8.so
 
 # Install libv8_libplatform.a (V8 >= 5.2.51)
-echo -e "create /usr/lib/libv8_libplatform.a\naddlib out/native/obj.target/src/libv8_libplatform.a\nsave\nend" | sudo ar -M
+echo -e "create /opt/v8/lib/libv8_libplatform.a\naddlib out/native/obj.target/src/libv8_libplatform.a\nsave\nend" | sudo ar -M
 
 # ... same for V8 < 5.2.51, libv8_libplatform.a is built in tools/gyp directory
-echo -e "create /usr/lib/libv8_libplatform.a\naddlib out/native/obj.target/tools/gyp/libv8_libplatform.a\nsave\nend" | sudo ar -M
+echo -e "create /opt/v8/lib/libv8_libplatform.a\naddlib out/native/obj.target/tools/gyp/libv8_libplatform.a\nsave\nend" | sudo ar -M
 ```
 
-* If you don't want to overwrite the system copy of v8, replace `/usr` in
-  the above commands with some other path like `/opt/v8` and then add
-  `--with-v8js=/opt/v8` to the php-v8js `./configure` command below.
-
 `libv8_libplatform.a` should not be copied directly since it's a thin
 archive, i.e. it contains only pointers to the build objects, which
 otherwise must not be deleted.  The simple mri-script converts the
@@ -93,7 +131,7 @@ cd /tmp
 git clone https://github.com/phpv8/v8js.git
 cd v8js
 phpize
-./configure
+./configure --with-v8js=/opt/v8
 make
 make test
 sudo make install