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go/types: don't panic in complex division

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Make sure that in complex division we reject divisors that would
underflow to zero when using the textbook complex-division method we
currently use.

This change does for go/types what golang.org/cl/42650 did for gc.

Fixes #20227

Change-Id: Iaa784ac5e60141f51c501eb0e3ce0e9c1c2993d0
Reviewed-on: https://go-review.googlesource.com/44590
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Alberto Donizetti 2017-05-13 19:11:44 +02:00
parent b1af5393d9
commit 3c745d750e
2 changed files with 18 additions and 5 deletions
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16
src/go/types/expr.go
View File

@ -800,12 +800,26 @@ func (check *Checker) binary(x *operand, e *ast.BinaryExpr, lhs, rhs ast.Expr, o
return
}
if (op == token.QUO || op == token.REM) && (x.mode == constant_ || isInteger(x.typ)) && y.mode == constant_ && constant.Sign(y.val) == 0 {
if op == token.QUO || op == token.REM {
// check for zero divisor
if (x.mode == constant_ || isInteger(x.typ)) && y.mode == constant_ && constant.Sign(y.val) == 0 {
check.invalidOp(y.pos(), "division by zero")
x.mode = invalid
return
}
// check for divisor underflow in complex division (see issue 20227)
if x.mode == constant_ && y.mode == constant_ && isComplex(x.typ) {
re, im := constant.Real(y.val), constant.Imag(y.val)
re2, im2 := constant.BinaryOp(re, token.MUL, re), constant.BinaryOp(im, token.MUL, im)
if constant.Sign(re2) == 0 && constant.Sign(im2) == 0 {
check.invalidOp(y.pos(), "division by zero")
x.mode = invalid
return
}
}
}
if x.mode == constant_ && y.mode == constant_ {
xval := x.val
yval := y.val

1
src/go/types/stdlib_test.go
View File

@ -171,7 +171,6 @@ func TestStdFixed(t *testing.T) {
"issue18459.go", // go/types doesn't check validity of //go:xxx directives
"issue18882.go", // go/types doesn't check validity of //go:xxx directives
"issue20232.go", // go/types handles larger constants than gc
"issue20227.go", // go/types does not handle this yet
"issue20529.go", // go/types does not have constraints on stack size
)
}