update readme and xenial, bionic installers

1 files changed, 41 insertions, 18 deletions

diff --git a/Debian/readme.md b/Debian/readme.md
index 8bd5e21..08f1411 100644
--- a/Debian/readme.md
+++ b/Debian/readme.md
@@ -5,22 +5,26 @@ Debian Installer Documentation
 It contains all the documenation for installers on Debian (Ubuntu 14.04 and above).
 
 
-## Separation of Ubuntu 14.04 and Ubuntu 16.04+ installers:
-1. Dependency of gnat : 
-	a. Ubuntu 14.04 : gnat (v4.6)
-	b. Ubuntu 16.04+: gnat-5 (v5.4)
-2. Dependency of llvm :
+## Differences in Ubuntu 14.04, Ubuntu 16.04 and Ubuntu 18.04 installers:
+1. Dependency on gnat :
+	- Ubuntu 14.04 : gnat (v4.6)
+	- Ubuntu 16.04+: gnat-5 (v5.4)
+2. Dependency on llvm :
 	- Available version on Ubuntu 14.04 : llvm (v3.4)
-	- Available version on Ubuntu 16.04+ : llvm (v3.4)
+	- Available version on Ubuntu 16.04 : llvm (v3.5)
+	- Available version on Ubuntu 18.04 : llvm (v6.0)
 	- Requires llvm version between 3.5 and 3.9 for compilation of GHDL with llvm config
+3. Dependency on gcc : 
+	- Ubuntu 14.04 and 16.04 : gcc (v5.4.0) is available without pie (i.e. position-independent executable)
+	- Ubuntu 18.04 : gcc (v7.4.0) is available with pie enabled as default option.
+	- Refer [this](https://github.com/ghdl/ghdl/issues/213) Github issue for dependency on gcc GHDL on Ubuntu 18.04 and above.
 
 
-##GHDL Compilation:
-1. Following steps are OS specific and GHDL executables should be generated on that system for distribution on 
-same OS configuration.
-2. For distribution of GHDL on Ubuntu 14.04, directly use the llvm code provided on GHDL's github page.
-3. For distribution of GHDL on Ubuntu 16.04 and above, follow the steps:
-	a. Download source code from GHDL's github page.
+## GHDL Compilation:
+1. Compilation of GHDL is OS specific and GHDL executables should be generated on that system for distribution on same OS configuration.
+2. For distribution of GHDL (v0.36) on Ubuntu 14.04, directly use the llvm executable provided on GHDL's Github page.
+3. For distribution of GHDL (v0.36) on Ubuntu 16.04 and above, follow the steps:
+	a. Download source code (v0.36) from GHDL's Github page.
 	b. Extract the tar file, open a terminal and change directory one-level inside.
 	c. First install gnat dependency as:
 	
@@ -28,21 +32,40 @@ same OS configuration.
 
 	d. Install llvm dependency and verify that version of llvm is between 3.5 and 3.9
 
-		$ sudo apt install llvm
+		- For Ubuntu 16.04 :
 
-	e. To compile GHDL, type following commands:
+			$ sudo apt install llvm
+
+		- For Ubuntu 18.04 :
+
+			$ sudo apt install llvm-3.9
+
+	e. Install clang dependency:
+
+		$ sudo apt install clang
+
+
+	f. To compile GHDL, type following commands:
 
 		$ mkdir -p install_dir
 		$ mkdir -p release
 		$ cd release/
-		$ ../configure --with-llvm-config --prefix=<absolute_path_to_install_dir>
+
+		- For Ubuntu 16.04 :
+
+			$ ../configure --with-llvm-config --prefix=<absolute_path_to_install_dir>
+
+		- For Ubuntu 18.04 :
+
+			$ ../configure --with-llvm-config=/usr/bin/llvm-config-3.9 --prefix=<absolute_path_to_install_dir>
+
 		$ make
 		$ make install
 
 	f. GHDL executables will be made in install_dir folder which can be used for distribution.
-	g. Note that target machine should have the same version of gnat as that of the source machine on which 
-	   GHDL was compiled.
+	g. Note that target machine should have the same version of gnat and OS as that of the source machine on which GHDL was compiled.
+
 
-##How to package GHDL executable with NGHDL?
+## How to package GHDL executable with NGHDL?
 1. Rename `install_dir` directory to the `ghdl-<version>` and compress it to `.tar.xz` format.
 2. Place this compressed file along with the installer file (`install-nghdl.sh`) in the `nghdl` folder.