Implemented PLUSARGS for FLI

The FLI does not offer any utility to easily grab the argc/argv from the
simulator. I use Questa's included TCL interpreter C API to access the
TCL 'argv' variable.

The 'argv' variable references the outer vsim call's arguments due to how
the current makefiles are setup, so the PLUSARGS variable was added back
to the outer call. PLUSARGS must also remain on the inner call for the
VPI implementation to work.

cocotb/share/lib/fli/FliCbHdl.cpp

@@ -26,6 +26,10 @@
 ******************************************************************************/
 
 #include "FliImpl.h"
+#include "mti.h"
+#undef DLLEXPORT  // redefinition in tcl.h causes warning
+#include "tcl.h"
+#include <limits>
 
 /**
  * @name    cleanup callback
@@ -140,6 +144,55 @@ int FliStartupCbHdl::arm_callback()
     return 0;
 }
 
+
+static void get_args(gpi_sim_info_t *info)
+{
+    /*  Necessary to implement PLUSARGS
+        There is no function available on the FLI to obtain argc+argv directly from the
+        simulator. To work around this we use the TCL interpreter that ships with Questa,
+        some TCL commands, and the TCL variable `argv` to obtain the simulator argc/argv.
+    */
+    info->argc = 0;
+    info->argv = NULL;
+
+    Tcl_Interp* interp = reinterpret_cast<Tcl_Interp*>(mti_Interp());
+
+    // get argc
+    if (mti_Cmd("llength $argv") != TCL_OK) {
+        return;
+    }
+    unsigned long argc_u = strtoul(interp->result, NULL, 10);
+    Tcl_ResetResult(interp);
+    if (argc_u > std::numeric_limits<int>::max()) {
+        return;
+    }
+    int argc = static_cast<int>(argc_u);
+    if (argc_u == 0) {
+        return;
+    }
+
+    // allocate storage for argv
+    char** argv = new char*[argc];
+
+    // get each argv and copy into internal storage
+    for (int i = 0; i < argc; i++) {
+        std::string cmd = "lindex $argv " + std::to_string(i);
+        if (mti_Cmd(cmd.c_str()) != TCL_OK) {
+            return;
+        }
+        argv[i] = new char[strlen(interp->result)+1];
+        strcpy(argv[i], interp->result);
+        Tcl_ResetResult(interp);
+    }
+
+    // set only if all operations succeed
+    info->argc = argc;
+    info->argv = argv;
+
+    // argv storage leaks here
+}
+
+
 int FliStartupCbHdl::run_callback()
 {
     gpi_sim_info_t sim_info;
@@ -168,8 +221,7 @@ int FliStartupCbHdl::run_callback()
 
 
     // copy in sim_info.product
-    sim_info.argc = 0;
-    sim_info.argv = NULL;
+    get_args(&sim_info);
     sim_info.product = &product[0];
     sim_info.version = &version[0];
 

cocotb/share/makefiles/simulators/Makefile.questa

@@ -148,7 +148,7 @@ $(COCOTB_RESULTS_FILE): $(SIM_BUILD)/runsim.do $(COCOTB_LIBS) $(INT_LIBS)
 
 	set -o pipefail; $(LIB_LOAD) MODULE=$(MODULE) TESTCASE=$(TESTCASE) TOPLEVEL=$(TOPLEVEL) COCOTB_SIM=1 \
 	GPI_EXTRA=$(GPI_EXTRA) TOPLEVEL_LANG=$(TOPLEVEL_LANG) PYTHONPATH=$(LIB_DIR):$(PWD):$(NEW_PYTHONPATH) \
-	$(CMD) $(RUN_ARGS) -do $(SIM_BUILD)/runsim.do 2>&1 | tee $(SIM_BUILD)/sim.log
+	$(CMD) $(RUN_ARGS) -do $(SIM_BUILD)/runsim.do $(PLUSARGS) 2>&1 | tee $(SIM_BUILD)/sim.log
 
 	# check that the file was actually created, since we can't set an exit code from cocotb
 	test -f $(COCOTB_RESULTS_FILE)

documentation/source/newsfragments/1256.feature.rst

@@ -0,0 +1 @@
+Questa now supports :envvar:`PLUSARGS`. This requires that ``tcl.h`` be present on the system. This is likely included in your installation of Questa. Otherwise, specify ``CXXFLAGS=-I/path/to/tcl/includedir``.