more flexible rebar.config

[namjae]

hi, I got following build error on Ubuntu 14.04LTS.

c_src/nifty_clangparse.c:10:27: fatal error: clang-c/Index.h: No such file or directory

this patch fixed above build error.

[kostis]

Thanks for your pull request. Is it possible to rebase this on the current master and squash both commits into one, so that we merge this by just clicking on github rather than manually?

[TheGeorge]

I am a bit reluctant to accept the pull request yet.

While I think we should absolutely use llvm-config to get the paths, we are using the paths in Travis to select the llvm version we are testing against.

I think we can select the version with an environment variable (like NIFTY_LLVM_VERSION) and set it in .travis.yml like this:

{port_specs, [
    {".*", "priv/nifty_clangparse.so", ["c_src/nifty_clangparse.c"], [{env,[
           {"CFLAGS", "`llvm-config$NIFTY_LLVM_VERION --cflags`"},
           {"LDFLAGS", "$LDFLAGS -lclang `llvm-config$NIFTY_LLVM_VERSION --ldflags`"}]}]},
    {"priv/nifty.so", ["c_src/nifty.c"]}
    ]}.

and also

--- a/.travis.yml
+++ b/.travis.yml
@@ -8,10 +8,10 @@ otp_release:
   - 17.4
   - 17.0
 env:
-  - CPATH=/usr/lib/llvm-3.4/include LIBRARY_PATH=/usr/lib/llvm-3.4/lib LD_LIBRARY_PATH=/usr/lib/llvm-3.4/lib
-  - CPATH=/usr/lib/gcc/x86_64-linux-gnu/4.6/include:/usr/lib/llvm-3.6/include LIBRARY_PATH=/usr/lib/llvm-3.6/lib LD_LIBRARY_PATH=/usr/lib/llvm-3.6/lib
-  - CPATH=/usr/lib/gcc/x86_64-linux-gnu/4.6/include:/usr/lib/llvm-3.7/include LIBRARY_PATH=/usr/lib/llvm-3.7/lib LD_LIBRARY_PATH=/usr/lib/llvm-3.7/lib
-  - CPATH=/usr/lib/gcc/x86_64-linux-gnu/4.6/include:/usr/lib/llvm-3.8/include LIBRARY_PATH=/usr/lib/llvm-3.8/lib LD_LIBRARY_PATH=/usr/lib/llvm-3.8/lib
+  - NIFTY_LLVM_VERSION=-3.4
+  - NIFTY_LLVM_VERSION=-3.6
+  - NIFTY_LLVM_VERSION=-3.7
+  - NIFTY_LLVM_VERSION=-3.8

[namjae]

hmm.. i don't know i just did was right or not.

[kostis]

@TheGeorge Yes, I think that your proposal kills two birds with one stone and we should adopt it.

Just make sure that the manual is updated to mention that nifty takes into account the environment variable NIFTY_LLVM_VERSION if it is set.

[TheGeorge]

this will be handled in #35