AltairZ80: Fix various static source scanning detected issues (Coverity Scan)

AltairZ80/altairz80_sys.c

@@ -428,10 +428,10 @@ static int32 DAsm(char *S, const uint32 *val, const int32 useZ80Mnemonics, const
         R[T1 - T] = '\0';
         printHex2(H, val[B++]);
         strcat(R, H);
-        strcat(R, T1 + 1);
+        strcat(R, T1 + 1); /* ok, since T1 is a short sub-string coming from one of the tables */
     }
     else
-        strcpy(R, T);
+        strcpy(R, T); /* ok, since T is a short string coming from one of the tables */
     if ( (P = strchr(R, '%')) ) {
         *P = C;
         if ( (P = strchr(P + 1, '%')) )

AltairZ80/flashwriter2.c

@@ -137,6 +137,10 @@ static t_stat fw2_attach(UNIT *uptr, CONST char *cptr)
         }
     }
 
+    if (i == FW2_MAX_BOARDS) {
+        return (SCPE_IERR);
+    }
+
     fw2_info[i] = (FW2_INFO *)calloc(1, sizeof(FW2_INFO));
     fw2_info[i]->uptr = uptr;
     fw2_info[i]->uptr->u3 = baseaddr;

AltairZ80/i8272.c

@@ -781,11 +781,11 @@ uint8 I8272_Write(const uint32 Addr, uint8 cData)
 
                 if(i8272_info->fdc_phase == EXEC_PHASE) {
                     switch(i8272_info->cmd[0] & 0x1F) {
-                        case I8272_READ_TRACK:
+                        case I8272_READ_TRACK:          /* intentional fallthrough */
                             sim_printf("I8272: " ADDRESS_FORMAT " Read a track (untested.)" NLP, PCX);
                             i8272_info->fdc_sector = 1; /* Read entire track from sector 1...eot */
-                        case I8272_READ_DATA:
+                        case I8272_READ_DATA:           /* intentional fallthrough */
-                        case I8272_READ_DELETED_DATA:
+                        case I8272_READ_DELETED_DATA:   /* intentional fallthrough */
                             disk_read = 1;
                         case I8272_WRITE_DATA:
                         case I8272_WRITE_DELETED_DATA:

AltairZ80/m68kdasm.c

@@ -3288,7 +3288,7 @@ unsigned int m68k_is_valid_instruction(unsigned int instruction, unsigned int cp
             if(g_instruction_table[instruction] == d68010_moves_32)
                 return 0;
             if(g_instruction_table[instruction] == d68010_rtd)
-                return 0;
+                return 0;   /* intentional fallthrough, older models have more invalid instructions */
         case M68K_CPU_TYPE_68010:
             if(g_instruction_table[instruction] == d68020_bcc_32)
                 return 0;

AltairZ80/m68kops.c

@@ -1993,6 +1993,7 @@ static opcode_handler_struct m68k_opcode_handler_table[] =
 void m68ki_build_opcode_table(void)
 {
     opcode_handler_struct *ostruct;
+    int cycle_cost;
     int instr;
     int i;
     int j;
@@ -2040,8 +2041,17 @@ void m68ki_build_opcode_table(void)
                 m68ki_instruction_jump_table[instr] = ostruct->opcode_handler;
                 for(k=0;k<NUM_CPU_TYPES;k++)
                     m68ki_cycles[k][instr] = ostruct->cycles[k];
+                // For all shift operations with known shift distance (encoded in instruction word), this is backported from MUSASHI Version 3.4
                 if((instr & 0xf000) == 0xe000 && (!(instr & 0x20)))
-                    m68ki_cycles[0][instr] = m68ki_cycles[1][instr] = ostruct->cycles[k] + ((((j-1)&7)+1)<<1);
+                {
+                    // On the 68000 and 68010 shift distance affect execution time.
+                    // Add the cycle cost of shifting; 2 times the shift distance
+                    cycle_cost = ((((i-1)&7)+1)<<1);
+                    m68ki_cycles[0][instr] += cycle_cost;
+                    m68ki_cycles[1][instr] += cycle_cost;
+                    // On the 68020 shift distance does not affect execution time
+                    m68ki_cycles[2][instr] += 0;
+                }
             }
         }
         ostruct++;

AltairZ80/mfdc.c

@@ -255,6 +255,9 @@ static t_stat mfdc_attach(UNIT *uptr, CONST char *cptr)
     }
 
     i = find_unit_index(uptr);
+    if (i == -1) {
+        return (SCPE_IERR);
+    }
 
     /* Default for new file is DSK */
     uptr->u3 = IMAGE_TYPE_DSK;
@@ -474,8 +477,7 @@ static uint8 MFDC_Read(const uint32 Addr)
                     case IMAGE_TYPE_DSK:
                         if(pDrive->uptr->fileref == NULL) {
                             sim_printf(".fileref is NULL!" NLP);
-                        } else {
+                        } else if (sim_fseek((pDrive->uptr)->fileref, sec_offset, SEEK_SET) == 0) {
-                            sim_fseek((pDrive->uptr)->fileref, sec_offset, SEEK_SET);
 #ifdef USE_VGI
                             rtn = sim_fread(sdata.raw, 1, MFDC_SECTOR_LEN, (pDrive->uptr)->fileref);
                             if (rtn != MFDC_SECTOR_LEN)
@@ -484,6 +486,8 @@ static uint8 MFDC_Read(const uint32 Addr)
                             if (rtn != 256)
 #endif /* USE_VGI */
                                 sim_printf("%s: sim_fread error. Result = %d." NLP, __FUNCTION__, rtn);
+                        } else {
+                            sim_printf("%s: sim_fseek error." NLP, __FUNCTION__);
                         }
                         break;
                     case IMAGE_TYPE_CPT:
@@ -601,13 +605,14 @@ static uint8 MFDC_Write(const uint32 Addr, uint8 cData)
                         case IMAGE_TYPE_DSK:
                             if(pDrive->uptr->fileref == NULL) {
                                 sim_printf(".fileref is NULL!" NLP);
-                            } else {
+                            } else if (sim_fseek((pDrive->uptr)->fileref, sec_offset, SEEK_SET) == 0) {
-                                sim_fseek((pDrive->uptr)->fileref, sec_offset, SEEK_SET);
 #ifdef USE_VGI
                                 sim_fwrite(sdata.raw, 1, MFDC_SECTOR_LEN, (pDrive->uptr)->fileref);
 #else
                                 sim_fwrite(sdata.u.data, 1, 256, (pDrive->uptr)->fileref);
 #endif /* USE_VGI */
+                            } else {
+                                sim_printf("%s: sim_fseek error." NLP, __FUNCTION__);
                             }
                             break;
                         case IMAGE_TYPE_CPT:

AltairZ80/nasm.h

@@ -260,7 +260,7 @@ typedef struct extop {          /* extended operand */
 #define MAXPREFIX 4
 
 typedef struct {                /* an instruction itself */
-    char *label;                /* the label defined, or NULL */
+    /* char *label; not needed */               /* the label defined, or NULL */
     int prefixes[MAXPREFIX];    /* instruction prefixes, if any */
     int nprefix;                /* number of entries in above */
     int opcode;                 /* the opcode - not just the string */