BIOS and DOS CON device: Make STOP key work the same way as CTRL+C and CTRL+BREAK

src/dos/dev_con.h

@@ -672,6 +672,12 @@ bool device_CON::Read(uint8_t * data,uint16_t * size) {
             continue;
         }
 
+        // Make STOP key work
+        if (IS_PC98_ARCH && DOS_BreakFlag) {
+            data[count++]=0x03; // CTRL+C
+            continue;
+        }
+
 		reg_ah=(IS_EGAVGA_ARCH)?0x10:0x0;
 
         /* FIXME: PC-98 emulation should eventually use CONIO emulation that

src/ints/bios.cpp

@@ -6972,11 +6972,18 @@ uint32_t BIOS_get_PC98_INT_STUB(void) {
 
 Bitu call_pc98_default_stop;
 
+extern bool DOS_BreakFlag;
+
 static Bitu pc98_default_stop_handler(void) {
     // INT 06h, which means someone pressed the STOP key... or the CPU is signalling an invalid opcode.
     // The overlap makes it extremely unclear.
     LOG_MSG("Invalid opcode or unhandled PC-98 STOP key interrupt 06h");
-	return CBRET_NONE;
+
+    // try to make it work as CTRL+BREAK in the built-in DOS environment.
+    if (!dos_kernel_disabled)
+        DOS_BreakFlag = true;
+
+    return CBRET_NONE;
 }
 
 /* NTS: Remember the 8259 is non-sentient, and the term "slave" is used in a computer programming context */

src/ints/bios_keyboard.cpp

@@ -1402,6 +1402,8 @@ static bool IsEnhancedKey(uint16_t &key) {
     return false;
 }
 
+extern bool DOS_BreakFlag;
+
 bool int16_unmask_irq1_on_read = true;
 bool int16_ah_01_cf_undoc = true;
 
@@ -1412,6 +1414,12 @@ Bitu INT16_Handler(void) {
         if (int16_unmask_irq1_on_read)
             PIC_SetIRQMask(1,false); /* unmask keyboard */
 
+        // HACK: Make STOP key work
+        if (IS_PC98_ARCH && DOS_BreakFlag) {
+            reg_ax=0;
+            return CBRET_NONE;
+        }
+
         if ((get_key(temp)) && (!IsEnhancedKey(temp))) {
             /* normal key found, return translated key in ax */
             reg_ax=temp;
@@ -1424,6 +1432,12 @@ Bitu INT16_Handler(void) {
         if (int16_unmask_irq1_on_read)
             PIC_SetIRQMask(1,false); /* unmask keyboard */
 
+        // HACK: Make STOP key work
+        if (IS_PC98_ARCH && DOS_BreakFlag) {
+            reg_ax=0;
+            return CBRET_NONE;
+        }
+
         if (get_key(temp)) {
             if (!IS_PC98_ARCH && ((temp&0xff)==0xf0) && (temp>>8)) {
                 /* special enhanced key, clear low part before returning key */