Usage of POINTER variable under PROCEDURE or other blocks result into compilation error (CoreNEURON)

[pramodk]

Context

#1622 has added the support for usage of POINTER variables for CoreNEURON. But, if we use such variable in block like PROCEDURE then we get compilation error.

Expected result/behavior

MOD file should compile just fine.

NEURON setup

• Version: master
• Installation method: default CMake build with coreneuron support

Minimal working example - MWE

• Update the existing test as:

diff --git a/test/coreneuron/mod/axial.inc b/test/coreneuron/mod/axial.inc
index cca9c26a..77aba1d5 100644
--- a/test/coreneuron/mod/axial.inc
+++ b/test/coreneuron/mod/axial.inc
@@ -26,6 +26,10 @@ ASSIGNED {
     pim (nA) : parent im
 }

+PROCEDURE foo() {
+    pim = pim + 1
+}
+

• Try to compile test MOD files:

➜  build git:(master) ✗ ./install/bin/nrnivmodl-core ../test/coreneuron/mod
[INFO] Running: make -j4 -f /Users/kumbhar/Downloads/nrn/build/install/share/coreneuron/nrnivmodl_core_makefile ROOT=/Users/kumbhar/Downloads/nrn/build/install MODS_PATH=x86_64/corenrn/mod2c BUILD_TYPE=SHARED NRN_PRCELLSTATE=0
Default NMODL flags:
x86_64/corenrn/mod2c/axial.cpp: In function 'int coreneuron::foo_axial(int, int, double*, coreneuron::Datum*, coreneuron::ThreadDatum*, coreneuron::NrnThread*, double)':
x86_64/corenrn/mod2c/axial.cpp:120:17: error: '_nt_data' was not declared in this scope
  120 | #define pim     _nt_data[_ppvar[2*_STRIDE]]
      |                 ^~~~~~~~
x86_64/corenrn/mod2c/axial.cpp:241:4: note: in expansion of macro 'pim'
  241 |    pim = pim + 1.0 ;
      |    ^~~
x86_64/corenrn/mod2c/axial_pp.cpp: In function 'int coreneuron::foo_AxialPP(int, int, double*, coreneuron::Datum*, coreneuron::ThreadDatum*, coreneuron::NrnThread*, double)':
x86_64/corenrn/mod2c/axial_pp.cpp:134:17: error: '_nt_data' was not declared in this scope
  134 | #define pim     _nt_data[_ppvar[4*_STRIDE]]
      |                 ^~~~~~~~
x86_64/corenrn/mod2c/axial_pp.cpp:333:4: note: in expansion of macro 'pim'
  333 |    pim = pim + 1.0 ;
      |    ^~~
make: *** [x86_64/corenrn/build/axial.o] Error 1
make: *** Waiting for unfinished jobs....
make: *** [x86_64/corenrn/build/axial_pp.o] Error 1

• CMake build commands:

git clone [email protected]:neuronsimulator/nrn.git
mkdir build && cd build
cmake .. -DCMAKE_INSTALL_PREFIX=`pwd`/install -DCORENRN_ENABLE_MPI=ON  -DNRN_ENABLE_CORENEURON=ON -DNRN_ENABLE_INTERVIEWS=OFF -DNRN_ENABLE_RX3D=OFF
cmake --build . --

Additional info

This issue came across while testing MOD file reported in suny-downstate-medical-center/netpyne#667.