Make the ngSpice_Circ(char** circa) more robust:

Error message when .end card is missing
Reset if .end card is missing, to allow loading
a netlist again.
NULL as last element is no longer required, but .end card
(this has been implicitedly assumed).
Remove a bug that skippoed the last line (the .end card).

src/frontend/inp.c

@@ -55,7 +55,7 @@ static struct card *mc_deck = NULL;
 static struct card *recent_deck = NULL;
 
 static void cktislinear(CKTcircuit *ckt, struct card *deck);
-void create_circbyline(char *line);
+void create_circbyline(char *line, bool reset, bool lastline);
 static bool doedit(char *filename);
 static void dotifeval(struct card *deck);
 static void eval_agauss(struct card *deck, char *fcn);
@@ -1716,11 +1716,17 @@ static void cktislinear(CKTcircuit *ckt, struct card *deck)
 char **circarray;
 
 
-void create_circbyline(char *line)
+void create_circbyline(char *line, bool reset, bool lastline)
 {
     static unsigned int linec = 0;
     static unsigned int n_elem_alloc = 0;
 
+    if (reset) {
+        linec = 0;
+        n_elem_alloc = 0;
+        tfree(circarray);
+    }
+
     /* Ensure up to 2 cards can be added */
     if (n_elem_alloc < linec + 2) {
         n_elem_alloc = n_elem_alloc == 0 ? 256 : 2 * n_elem_alloc;
@@ -1754,6 +1760,10 @@ void create_circbyline(char *line)
         linec = 0;
         n_elem_alloc = 0;
     }
+    /* If the .end statement is missing */
+    else if (lastline) {
+        fprintf(stderr, "Error: .end statement is missing in netlist!\n");
+    }
 } /* end of function create_circbyline */
 
 
@@ -1766,7 +1776,7 @@ void com_circbyline(wordlist *wl)
        This memory will be released line by line in inp_source(). */
 
     char *newline = wl_flatten(wl);
-    create_circbyline(newline);
+    create_circbyline(newline, FALSE, FALSE);
 }
 
 /* handle .if('expr') ... .elseif('expr') ... .else ... .endif statements.

src/include/ngspice/sharedspice.h

@@ -371,7 +371,7 @@ int  ngSpice_Init_Evt(SendEvtData* sevtdata, SendInitEvtData* sinitevtdata, void
 /* send a circuit to ngspice.dll
    The circuit description is a dynamic array
    of char*. Each char* corresponds to a single circuit
-   line. The last entry of the array has to be a NULL */
+   line. The last entry of the array has to be a .end card. */
 IMPEXP
 int ngSpice_Circ(char** circarray);
 

src/sharedspice.c

@@ -194,7 +194,7 @@ extern struct comm spcp_coms[ ];
 extern void DevInit(void);
 extern int SIMinit(IFfrontEnd *frontEnd, IFsimulator **simulator);
 extern wordlist *cp_varwl(struct variable *var);
-extern void create_circbyline(char *line);
+extern void create_circbyline(char *line, bool reset, bool lastline);
 
 void exec_controls(wordlist *shcontrols);
 void rem_controls(void);
@@ -971,6 +971,7 @@ IMPEXP
 int ngSpice_Circ(char** circa){
     int entries = 0, i;
     char* newline;
+    bool reset = FALSE, lastline = FALSE;
 
     if ( ! setjmp(errbufm) ) {
         intermj = 0;
@@ -978,14 +979,23 @@ int ngSpice_Circ(char** circa){
         /* count the entries */
         while (circa[entries]) {
             entries++;
+            char* line = circa[entries - 1];
+            if (ciprefix(".end", line) && (line[4] == '\0' || isspace_c(line[4])))
+                break;
         }
-        entries--; /* don't send the empty line */
+
         if (ft_ngdebug)
             fprintf(stdout, "\nngspiceCirc: received netlist array with %d entries\n", entries);
         /* create a local copy (to be freed in inpcom.c) */
         for (i = 0; i < entries; i++) {
             newline = copy(circa[i]);
-            create_circbyline(newline);
+            if (i == 0)
+                reset = TRUE;
+            else
+                reset = FALSE;
+            if (i == entries - 1)
+                lastline = TRUE;
+            create_circbyline(newline, reset, lastline);
         }
         return 0;
     }