updated README.md

README.md

@@ -17,9 +17,11 @@ limitations under the License.
 Translates MuIR in text form and creates a correspondinng boot image, or generates C code that does the same.
 
 ## Preqrequisites:
-* You will need a C++14 compiler (tested with g++ 5.4.0)
-* You will ned the GNU Multiple Precision Arithmetic Library (tested with GMP 6.1.0)
+* You will need a C++14 compiler (tested with clang++6.0.0)
+* You will need the GNU Multiple Precision Arithmetic Library (tested with GMP 6.1.0)
 * You will need the Antlr4 C++ runtime, use `git clone https://github.com/antlr/antlr4.git` and follow the build instructions in `runtime/Cpp/README.md`.
+  - Note that on some systems, `cmake` does not recognize the correct toolchain to use. So, we recommand setting both `CC` and `CXX` environment variables, before running the `cmake ..` command.
+
   Once you've done that, copy the include files and the libraries  (where $antlr4 is the root of the antlr4 git repo you just cloned):
 ```
     cp -r $antlr4/runtime/Cpp/run/usr/local/include/antlr4-runtime/* ./include/
@@ -30,11 +32,20 @@ also set the environement variable `MU_ZEBU` to the locatation of the mu-impl-fa
 
 ## C Code prerequisites
 To run the generated C code you will need:
-* To link with Mu (make sure that the environment variable `MU_ZEBU` is set to the locatation of the mu-impl-fast source code)
-* A C compiler (tested with GCC version 5.4.0, whith the default `-std=gnu11`)
+* To link with Mu
+  - Make sure that the environment variable `MU_ZEBU` is set to the locatation of the mu-impl-fast source code,
+  - Make sure to set the environment variable `ZEBU_BUILD` to the proper value (either `release` or `debug`)
+* A C compiler (tested with GCC version 5.4.0, with the default `-std=gnu11`)
 
 ## Building
-Run `make` or if you don't have Mu run `make no_mu`. If you're getting load errors, try `make static`.
+Run 
+```
+export ANTRL_HOME=$antlr4/runtime/Cpp/run
+make
+``` 
+where $antlr4 is the root of the antlr4 git repo you just cloned.
+
+If you don't have Mu run `make no_mu`. If you're getting load errors, try `make static`.
 
 ## Usage
 `LD_LIBRARY_PATH=./lib muc -r [-f primordial-function-name] bundle1.mu... bootimage`