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cvm: implement stack underflow errors

This commit is contained in:
Virgil Dupras 2020-06-26 17:55:10 -04:00
parent 9021e5f6e0
commit fc3919863f
3 changed files with 22 additions and 6 deletions

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@ -1,4 +1,4 @@
TARGETS = forth
TARGETS = forth stage
OBJS = vm.o
BLKPACK = ../tools/blkpack
BLKUNPACK = ../tools/blkunpack
@ -18,17 +18,19 @@ stage: stage.c $(OBJS) blkfs
blkfs: $(BLKPACK)
$(BLKPACK) ../blk > $@
forth: forth.c $(OBJS) blkfs
forth: forth.c $(OBJS)
$(CC) forth.c $(OBJS) -lncurses -o $@
vm.o: vm.c
stage: stage.c $(OBJS)
$(CC) stage.c $(OBJS) -lncurses -o $@
vm.o: vm.c blkfs
$(CC) -DFBIN_PATH=\"`pwd`/forth.bin\" -DBLKFS_PATH=\"`pwd`/blkfs\" -c -o vm.o vm.c
.PHONY: updatebootstrap
updatebootstrap: stage xcomp.fs pack
./stage < xcomp.fs > new.bin
mv new.bin forth.bin
.PHONY: pack
pack:

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@ -67,12 +67,20 @@ static void sw(word addr, word val) {
vm.mem[addr] = val;
vm.mem[addr+1] = val >> 8;
}
static word pop() { return vm.mem[vm.SP++] | vm.mem[vm.SP++] << 8; }
static word pop() {
if (vm.uflw) return 0;
if (vm.SP >= SP_ADDR) { vm.uflw = true; }
return vm.mem[vm.SP++] | vm.mem[vm.SP++] << 8;
}
static void push(word x) {
vm.SP -= 2; sw(vm.SP, x);
if (vm.SP < vm.minSP) { vm.minSP = vm.SP; }
}
static word popRS() { word x = gw(vm.RS); vm.RS -= 2; return x; }
static word popRS() {
if (vm.uflw) return 0;
if (vm.RS <= RS_ADDR) { vm.uflw = true; }
word x = gw(vm.RS); vm.RS -= 2; return x;
}
static void pushRS(word val) {
vm.RS += 2; sw(vm.RS, val);
if (vm.RS > vm.maxRS) { vm.maxRS = vm.RS; }
@ -351,6 +359,7 @@ VM* VM_init() {
vm.IP = gw(0x04) + 1; // BOOT
sw(SYSVARS+0x02, gw(0x08)); // CURRENT
sw(SYSVARS+0x04, gw(0x08)); // HERE
vm.uflw = false;
vm.running = true;
return &vm;
}
@ -369,6 +378,10 @@ bool VM_steps(int n) {
word wordref = gw(vm.IP);
vm.IP += 2;
execute(wordref);
if (vm.uflw) {
vm.uflw = false;
execute(gw(0x06)); /* uflw */
}
n--;
}
return vm.running;

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@ -36,6 +36,7 @@ typedef struct {
word maxRS;
word minSP;
bool running;
bool uflw;
} VM;
VM* VM_init();