tools/emul: add "Min SP" debug value

This gives the maximum size of the stack at any given moment during the
execution of the program. It's useful to figure out if the stack gets
dangerously close to the heap.

tools/emul/bshell/shell.c

@@ -186,5 +186,6 @@ int main()
     termInfo.c_lflag |= ECHO;
     termInfo.c_lflag |= ICANON;
     tcsetattr(0, TCSAFLUSH, &termInfo);
+    emul_printdebug();
     return 0;
 }

tools/emul/emul.c

@@ -48,6 +48,7 @@ Machine* emul_init()
 {
     memset(m.mem, 0, 0x10000);
     m.ramstart = 0;
+    m.minsp = 0xffff;
     for (int i=0; i<0x100; i++) {
         m.iord[i] = NULL;
         m.iowr[i] = NULL;
@@ -65,6 +66,10 @@ bool emul_step()
 {
     if (!m.cpu.halted) {
         Z80Execute(&m.cpu);
+        ushort newsp = m.cpu.R1.wr.SP;
+        if (newsp != 0 && newsp < m.minsp) {
+            m.minsp = newsp;
+        }
         return true;
     } else {
         return false;
@@ -75,3 +80,8 @@ void emul_loop()
 {
     while (emul_step());
 }
+
+void emul_printdebug()
+{
+    fprintf(stderr, "Min SP: %04x\n", m.minsp);
+}

tools/emul/emul.h

@@ -2,15 +2,17 @@
 #include <stdbool.h>
 #include "libz80/z80.h"
 
-typedef uint8_t (*IORD) ();
-typedef void (*IOWR) (uint8_t data);
+typedef byte (*IORD) ();
+typedef void (*IOWR) (byte data);
 
 typedef struct {
     Z80Context cpu;
-    uint8_t mem[0x10000];
+    byte mem[0x10000];
     // Set to non-zero to specify where ROM ends. Any memory write attempt
     // below ramstart will trigger a warning.
-    uint16_t ramstart;
+    ushort ramstart;
+    // The minimum value reached by SP at any point during execution.
+    ushort minsp;
     // Array of 0x100 function pointers to IO read and write routines. Leave to
     // NULL when IO port is unhandled.
     IORD iord[0x100];
@@ -20,3 +22,4 @@ typedef struct {
 Machine* emul_init();
 bool emul_step();
 void emul_loop();
+void emul_printdebug();

tools/emul/shell/shell.c

@@ -186,5 +186,6 @@ int main()
     termInfo.c_lflag |= ECHO;
     termInfo.c_lflag |= ICANON;
     tcsetattr(0, TCSAFLUSH, &termInfo);
+    emul_printdebug();
     return 0;
 }