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Enable illegal BCD break/debugging

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* Debugging builds will now segfault if an illegal BCD is encountered
    * Presumably current x86 undefined behavior does not 100% correspond to 6502
      undefined behavior ... (this bears further investigation)
This commit is contained in:
Aaron Culliney 2014-02-22 09:45:19 -08:00
parent 6724e06500
commit 43ada45a36
2 changed files with 41 additions and 1 deletions
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31
src/asm386/cpu.S
View File

@ -343,8 +343,35 @@
adcb %al, A_Reg; \
FlagNVZC
// REFACTOR:
#ifndef NDEBUG
#define DebugBCDCheck \
testb $0x80, A_Reg; \
jz 6f; \
testb $0x60, A_Reg; \
jz 6f; \
call SN(c_debug_illegal_bcd); \
6: testb $0x08, A_Reg; \
jz 7f; \
testb $0x06, A_Reg; \
jz 7f; \
call SN(c_debug_illegal_bcd); \
7: testb $0x80, %al; \
jz 8f; \
testb $0x60, %al; \
jz 8f; \
call SN(c_debug_illegal_bcd); \
8: testb $0x08, %al; \
jz 9f; \
testb $0x06, %al; \
jz 9f; \
call SN(c_debug_illegal_bcd); \
9:
#else
#define DebugBCDCheck
#endif
#define DoADC_d GetFromEA_B \
DebugBCDCheck \
bt $C_Flag_Bit, FF_Reg; \
adcb A_Reg, %al; \
daa; \
@ -445,6 +472,7 @@
FlagNVZC
#define DoSBC_d GetFromEA_B \
DebugBCDCheck \
bt $C_Flag_Bit, FF_Reg; \
cmc; \
xchgb A_Reg, %al; \
@ -1619,6 +1647,7 @@ op_RTS:
/* ----------------------------------
SBC instructions
SuBtract memory from accumulator with Borrow
---------------------------------- */
op_SBC_dec:

11
src/misc.c
View File

@ -76,6 +76,17 @@ void *base_c5rom;
uint8_t *base_cxrom;
/* -------------------------------------------------------------------------
c_debug_illegal_bcd - illegal BCD (decimal mode) computation
------------------------------------------------------------------------- */
void c_debug_illegal_bcd()
{
ERRLOG("Illegal/undefined BCD operation encountered, debug break on c_debug_illegal_bcd to debug...");
char *ptr = (char*)0x0bad;
*ptr = 0x1337; // segfault
}
/* -------------------------------------------------------------------------
c_set_altchar() - set alternate character set
------------------------------------------------------------------------- */