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compiler: make writeJumps return error for bad jumps

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The script is invalid anyway so it is better to notify user.
This commit is contained in:
Evgenii Stratonikov 2020-02-21 11:57:24 +03:00
parent 5e229d84d4
commit 177b725dc1
1 changed files with 16 additions and 8 deletions
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24
pkg/compiler/codegen.go
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@ -1203,7 +1203,9 @@ func CodeGen(info *buildInfo) ([]byte, error) {
return nil, c.prog.Err
}
buf := c.prog.Bytes()
c.writeJumps(buf)
if err := c.writeJumps(buf); err != nil {
return nil, err
}
return buf, nil
}
@ -1218,20 +1220,26 @@ func (c *codegen) resolveFuncDecls(f *ast.File) {
}
}
func (c *codegen) writeJumps(b []byte) {
func (c *codegen) writeJumps(b []byte) error {
ctx := vm.NewContext(b)
for op, _, err := ctx.Next(); err == nil && ctx.NextIP() < len(b); op, _, err = ctx.Next() {
switch op {
case opcode.JMP, opcode.JMPIFNOT, opcode.JMPIF, opcode.CALL:
// we can't use arg returned by ctx.Next() because it is copied
arg := b[ctx.NextIP()-2:]
nextIP := ctx.NextIP()
arg := b[nextIP-2:]
index := int16(binary.LittleEndian.Uint16(arg))
if int(index) > len(c.l) || int(index) < 0 {
continue
index := binary.LittleEndian.Uint16(arg)
if int(index) > len(c.l) {
return fmt.Errorf("unexpected label number: %d (max %d)", index, len(c.l))
}
offset := uint16(c.l[index] - ctx.NextIP() + 3)
binary.LittleEndian.PutUint16(arg, offset)
offset := c.l[index] - nextIP + 3
if offset > math.MaxUint16 {
return fmt.Errorf("label offset is too big at the instruction %d: %d (max %d)",
nextIP-3, offset, math.MaxUint16)
}
binary.LittleEndian.PutUint16(arg, uint16(offset))
}
}
return nil
}