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SA4003: check for integer literals
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Closes: gh-1470
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@dominikh
dominikh committed Nov 10, 2023
1 parent e67d98f commit 5447921
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Showing 2 changed files with 86 additions and 31 deletions.
102 changes: 71 additions & 31 deletions staticcheck/lint.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ import (
"go/token"
"go/types"
htmltemplate "html/template"
"math"
"net/http"
"os"
"reflect"
Expand Down Expand Up @@ -1990,6 +1991,9 @@ func CheckNilMaps(pass *analysis.Pass) (interface{}, error) {

func CheckExtremeComparison(pass *analysis.Pass) (interface{}, error) {
isobj := func(expr ast.Expr, name string) bool {
if name == "" {
return false
}
sel, ok := expr.(*ast.SelectorExpr)
if !ok {
return false
Expand All @@ -2005,50 +2009,86 @@ func CheckExtremeComparison(pass *analysis.Pass) (interface{}, error) {
return
}

var max string
var min string
// We only check for the math constants and integer literals, not for all constant expressions. This is to avoid
// false positives when constant values differ under different build tags.
var (
maxMathConst string
minMathConst string
maxLiteral constant.Value
minLiteral constant.Value
)

switch basic.Kind() {
case types.Uint8:
max = "math.MaxUint8"
maxMathConst = "math.MaxUint8"
minLiteral = constant.MakeUint64(0)
maxLiteral = constant.MakeUint64(math.MaxUint8)
case types.Uint16:
max = "math.MaxUint16"
maxMathConst = "math.MaxUint16"
minLiteral = constant.MakeUint64(0)
maxLiteral = constant.MakeUint64(math.MaxUint16)
case types.Uint32:
max = "math.MaxUint32"
maxMathConst = "math.MaxUint32"
minLiteral = constant.MakeUint64(0)
maxLiteral = constant.MakeUint64(math.MaxUint32)
case types.Uint64:
max = "math.MaxUint64"
maxMathConst = "math.MaxUint64"
minLiteral = constant.MakeUint64(0)
maxLiteral = constant.MakeUint64(math.MaxUint64)
case types.Uint:
max = "math.MaxUint64"
// TODO(dh): we could chose 32 bit vs 64 bit depending on the file's build tags
maxMathConst = "math.MaxUint64"
minLiteral = constant.MakeUint64(0)
maxLiteral = constant.MakeUint64(math.MaxUint64)

case types.Int8:
min = "math.MinInt8"
max = "math.MaxInt8"
minMathConst = "math.MinInt8"
maxMathConst = "math.MaxInt8"
minLiteral = constant.MakeInt64(math.MinInt8)
maxLiteral = constant.MakeInt64(math.MaxInt8)
case types.Int16:
min = "math.MinInt16"
max = "math.MaxInt16"
minMathConst = "math.MinInt16"
maxMathConst = "math.MaxInt16"
minLiteral = constant.MakeInt64(math.MinInt16)
maxLiteral = constant.MakeInt64(math.MaxInt16)
case types.Int32:
min = "math.MinInt32"
max = "math.MaxInt32"
minMathConst = "math.MinInt32"
maxMathConst = "math.MaxInt32"
minLiteral = constant.MakeInt64(math.MinInt32)
maxLiteral = constant.MakeInt64(math.MaxInt32)
case types.Int64:
min = "math.MinInt64"
max = "math.MaxInt64"
minMathConst = "math.MinInt64"
maxMathConst = "math.MaxInt64"
minLiteral = constant.MakeInt64(math.MinInt64)
maxLiteral = constant.MakeInt64(math.MaxInt64)
case types.Int:
min = "math.MinInt64"
max = "math.MaxInt64"
// TODO(dh): we could chose 32 bit vs 64 bit depending on the file's build tags
minMathConst = "math.MinInt64"
maxMathConst = "math.MaxInt64"
minLiteral = constant.MakeInt64(math.MinInt64)
maxLiteral = constant.MakeInt64(math.MaxInt64)
}

if (expr.Op == token.GTR || expr.Op == token.GEQ) && isobj(expr.Y, max) ||
(expr.Op == token.LSS || expr.Op == token.LEQ) && isobj(expr.X, max) {
report.Report(pass, expr, fmt.Sprintf("no value of type %s is greater than %s", basic, max))
}
if expr.Op == token.LEQ && isobj(expr.Y, max) ||
expr.Op == token.GEQ && isobj(expr.X, max) {
report.Report(pass, expr, fmt.Sprintf("every value of type %s is <= %s", basic, max))
isLiteral := func(expr ast.Expr, c constant.Value) bool {
if c == nil {
return false
}
return code.IsIntegerLiteral(pass, expr, c)
}

isZeroLiteral := func(expr ast.Expr) bool {
return code.IsIntegerLiteral(pass, expr, constant.MakeInt64(0))
}

if (expr.Op == token.GTR || expr.Op == token.GEQ) && (isobj(expr.Y, maxMathConst) || isLiteral(expr.Y, maxLiteral)) ||
(expr.Op == token.LSS || expr.Op == token.LEQ) && (isobj(expr.X, maxMathConst) || isLiteral(expr.X, maxLiteral)) {
report.Report(pass, expr, fmt.Sprintf("no value of type %s is greater than %s", basic, maxMathConst))
}

if expr.Op == token.LEQ && (isobj(expr.Y, maxMathConst) || isLiteral(expr.Y, maxLiteral)) ||
expr.Op == token.GEQ && (isobj(expr.X, maxMathConst) || isLiteral(expr.X, maxLiteral)) {
report.Report(pass, expr, fmt.Sprintf("every value of type %s is <= %s", basic, maxMathConst))
}

if (basic.Info() & types.IsUnsigned) != 0 {
if (expr.Op == token.LSS && isZeroLiteral(expr.Y)) ||
(expr.Op == token.GTR && isZeroLiteral(expr.X)) {
Expand All @@ -2059,13 +2099,13 @@ func CheckExtremeComparison(pass *analysis.Pass) (interface{}, error) {
report.Report(pass, expr, fmt.Sprintf("every value of type %s is >= 0", basic))
}
} else {
if (expr.Op == token.LSS || expr.Op == token.LEQ) && isobj(expr.Y, min) ||
(expr.Op == token.GTR || expr.Op == token.GEQ) && isobj(expr.X, min) {
report.Report(pass, expr, fmt.Sprintf("no value of type %s is less than %s", basic, min))
if (expr.Op == token.LSS || expr.Op == token.LEQ) && (isobj(expr.Y, minMathConst) || isLiteral(expr.Y, minLiteral)) ||
(expr.Op == token.GTR || expr.Op == token.GEQ) && (isobj(expr.X, minMathConst) || isLiteral(expr.X, minLiteral)) {
report.Report(pass, expr, fmt.Sprintf("no value of type %s is less than %s", basic, minMathConst))
}
if expr.Op == token.GEQ && isobj(expr.Y, min) ||
expr.Op == token.LEQ && isobj(expr.X, min) {
report.Report(pass, expr, fmt.Sprintf("every value of type %s is >= %s", basic, min))
if expr.Op == token.GEQ && (isobj(expr.Y, minMathConst) || isLiteral(expr.Y, minLiteral)) ||
expr.Op == token.LEQ && (isobj(expr.X, minMathConst) || isLiteral(expr.X, minLiteral)) {
report.Report(pass, expr, fmt.Sprintf("every value of type %s is >= %s", basic, minMathConst))
}
}

Expand Down
15 changes: 15 additions & 0 deletions staticcheck/testdata/src/example.com/CheckExtremeComparison/CheckExtremeComparison.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -40,4 +40,19 @@ func fn1() {
_ = i8 <= math.MinInt8 //@ diag(`no value of type int8 is less than math.MinInt8`)
_ = i8 < math.MinInt8 //@ diag(`no value of type int8 is less than math.MinInt8`)
_ = i8 >= math.MinInt8 //@ diag(`every value of type int8 is >= math.MinInt8`)

_ = i8 > -128
_ = i8 >= -128 //@ diag(`every value of type int8 is >= math.MinInt8`)
_ = i8 < 127
_ = i8 <= 127 //@ diag(`every value of type int8 is <= math.MaxInt8`)
_ = i8 > 127 //@ diag(`no value of type int8 is greater than math.MaxInt8`)
_ = i8 >= 127 //@ diag(`no value of type int8 is greater than math.MaxInt8`)

_ = u8 < 255
_ = u8 <= 255 //@ diag(`every value of type uint8 is <= math.MaxUint8`)
_ = u8 > 255 //@ diag(`no value of type uint8 is greater than math.MaxUint8`)
_ = u8 >= 255 //@ diag(`no value of type uint8 is greater than math.MaxUint8`)

const k = 255
_ = u8 <= k
}

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