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Removed integerOverflowOptimization checking and merged functionality into invalidTestForOverflow

This commit is contained in:
Daniel Marjamäki 2021-01-05 11:38:19 +01:00
parent abd6c00c82
commit b3b7ecc7ea
6 changed files with 148 additions and 208 deletions
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123
lib/checkcondition.cpp
View File

@ -39,6 +39,7 @@
#include <utility>
// CWE ids used
static const struct CWE uncheckedErrorConditionCWE(391U);
static const struct CWE CWE398(398U); // Indicator of Poor Code Quality
static const struct CWE CWE570(570U); // Expression is Always False
static const struct CWE CWE571(571U); // Expression is Always True
@ -1494,63 +1495,103 @@ void CheckCondition::alwaysTrueFalseError(const Token *tok, const ValueFlow::Val
void CheckCondition::checkInvalidTestForOverflow()
{
// Interesting blogs:
// https://www.airs.com/blog/archives/120
// https://kristerw.blogspot.com/2016/02/how-undefined-signed-overflow-enables.html
// https://research.checkpoint.com/2020/optout-compiler-undefined-behavior-optimizations/
// x + c < x -> false
// x + c <= x -> false
// x + c > x -> true
// x + c >= x -> true
// x + y < x -> y < 0
if (!mSettings->isEnabled(Settings::WARNING))
return;
const SymbolDatabase *symbolDatabase = mTokenizer->getSymbolDatabase();
for (const Scope * scope : symbolDatabase->functionScopes) {
for (const Token* tok = scope->bodyStart; tok != scope->bodyEnd; tok = tok->next()) {
if (!tok->isComparisonOp() || !tok->astOperand1() || !tok->astOperand2())
for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) {
if (!Token::Match(tok, "<|<=|>=|>") || !tok->isBinaryOp())
continue;
const Token *calcToken, *exprToken;
const Token *lhsTokens[2] = {tok->astOperand1(), tok->astOperand2()};
for (const Token *lhs: lhsTokens) {
std::string cmp = tok->str();
if (lhs == tok->astOperand2())
cmp[0] = (cmp[0] == '<') ? '>' : '<';
if (!Token::Match(lhs, "[+-]") || !lhs->isBinaryOp())
continue;
const bool isSignedInteger = lhs->valueType() && lhs->valueType()->isIntegral() && lhs->valueType()->sign == ValueType::Sign::SIGNED;
const bool isPointer = lhs->valueType() && lhs->valueType()->pointer > 0;
if (!isSignedInteger && !isPointer)
continue;
const Token *exprTokens[2] = {lhs->astOperand1(), lhs->astOperand2()};
for (const Token *expr: exprTokens) {
if (lhs->str() == "-" && expr == lhs->astOperand2())
continue; // TODO?
if (expr->hasKnownIntValue())
continue;
if (!isSameExpression(mTokenizer->isCPP(),
true,
expr,
lhs->astSibling(),
mSettings->library,
true,
false))
continue;
const Token * const other = expr->astSibling();
// x [+-] c cmp x
if ((other->isNumber() && other->getKnownIntValue() > 0) ||
(!other->isNumber() && other->valueType() && other->valueType()->isIntegral() && other->valueType()->sign == ValueType::Sign::UNSIGNED)) {
bool result;
if (Token::Match(tok, "<|>=") && tok->astOperand1()->str() == "+") {
calcToken = tok->astOperand1();
exprToken = tok->astOperand2();
result = (tok->str() == ">=");
} else if (Token::Match(tok, ">|<=") && tok->astOperand2()->str() == "+") {
calcToken = tok->astOperand2();
exprToken = tok->astOperand1();
result = (tok->str() == "<=");
} else
continue;
// Only warn for signed integer overflows and pointer overflows.
if (!(calcToken->valueType() && (calcToken->valueType()->pointer || calcToken->valueType()->sign == ValueType::Sign::SIGNED)))
continue;
if (!(exprToken->valueType() && (exprToken->valueType()->pointer || exprToken->valueType()->sign == ValueType::Sign::SIGNED)))
continue;
const Token *termToken;
if (isSameExpression(mTokenizer->isCPP(), true, exprToken, calcToken->astOperand1(), mSettings->library, true, false))
termToken = calcToken->astOperand2();
else if (isSameExpression(mTokenizer->isCPP(), true, exprToken, calcToken->astOperand2(), mSettings->library, true, false))
termToken = calcToken->astOperand1();
if (lhs->str() == "+")
result = (cmp == ">" || cmp == ">=");
else
result = (cmp == "<" || cmp == "<=");
invalidTestForOverflow(tok, lhs->valueType(), result ? "true" : "false");
continue;
}
if (!termToken)
// x + y cmp x
if (lhs->str() == "+" && other->varId() > 0) {
const std::string result = other->str() + cmp + "0";
invalidTestForOverflow(tok, lhs->valueType(), result);
continue;
}
// Only warn when termToken is always positive
if (termToken->valueType() && termToken->valueType()->sign == ValueType::Sign::UNSIGNED)
invalidTestForOverflow(tok, result);
else if (termToken->isNumber() && MathLib::isPositive(termToken->str()))
invalidTestForOverflow(tok, result);
// x - y cmp x
if (lhs->str() == "-" && other->varId() > 0) {
std::string cmp2 = cmp;
cmp2[0] = (cmp[0] == '<') ? '>' : '<';
const std::string result = other->str() + cmp2 + "0";
invalidTestForOverflow(tok, lhs->valueType(), result);
continue;
}
}
}
}
}
void CheckCondition::invalidTestForOverflow(const Token* tok, bool result)
void CheckCondition::invalidTestForOverflow(const Token* tok, const ValueType *valueType, const std::string &replace)
{
const std::string errmsg = "Invalid test for overflow '" +
(tok ? tok->expressionString() : std::string("x + u < x")) +
"'. Condition is always " +
std::string(result ? "true" : "false") +
" unless there is overflow, and overflow is undefined behaviour.";
reportError(tok, Severity::warning, "invalidTestForOverflow", errmsg, (result ? CWE571 : CWE570), false);
const std::string expr = (tok ? tok->expressionString() : std::string("x + c < x"));
const std::string overflow = (valueType && valueType->pointer) ? "pointer overflow" : "signed integer overflow";
std::string errmsg =
"Invalid test for overflow '" + expr + "'; " + overflow + " is undefined behavior.";
if (replace == "false" || replace == "true")
errmsg += " Some mainstream compilers remove such overflow tests when optimising the code and assume it's always " + replace + ".";
else
errmsg += " Some mainstream compilers removes handling of overflows when optimising the code and change the code to '" + replace + "'.";
reportError(tok, Severity::warning, "invalidTestForOverflow", errmsg, uncheckedErrorConditionCWE, false);
}

7
lib/checkcondition.h
View File

@ -35,6 +35,7 @@ class Settings;
class Token;
class Tokenizer;
class ErrorLogger;
class ValueType;
/// @addtogroup Checks
/// @{
@ -155,7 +156,7 @@ private:
void alwaysTrueFalseError(const Token *tok, const ValueFlow::Value *value);
void invalidTestForOverflow(const Token* tok, bool result);
void invalidTestForOverflow(const Token* tok, const ValueType *valueType, const std::string &replace);
void pointerAdditionResultNotNullError(const Token *tok, const Token *calc);
void duplicateConditionalAssignError(const Token *condTok, const Token* assignTok);
@ -179,7 +180,7 @@ private:
c.moduloAlwaysTrueFalseError(nullptr, "1");
c.clarifyConditionError(nullptr, true, false);
c.alwaysTrueFalseError(nullptr, nullptr);
c.invalidTestForOverflow(nullptr, false);
c.invalidTestForOverflow(nullptr, nullptr, "false");
c.pointerAdditionResultNotNullError(nullptr, nullptr);
c.duplicateConditionalAssignError(nullptr, nullptr);
}
@ -202,7 +203,7 @@ private:
"- Mutual exclusion over || always evaluating to true\n"
"- Comparisons of modulo results that are always true/false.\n"
"- Known variable values => condition is always true/false\n"
"- Invalid test for overflow (for example 'ptr+u < ptr'). Condition is always false unless there is overflow, and overflow is undefined behaviour.\n";
"- Invalid test for overflow. Some mainstream compilers remove such overflow tests when optimising code.\n";
}
};
/// @}

91
lib/checktype.cpp
View File

@ -223,97 +223,6 @@ void CheckType::integerOverflowError(const Token *tok, const ValueFlow::Value &v
value.isInconclusive());
}
//---------------------------------------------------------------------------------
// Checking for code patterns that might be optimised differently by the compilers
//---------------------------------------------------------------------------------
void CheckType::checkIntegerOverflowOptimisations()
{
// Interesting blogs:
// https://www.airs.com/blog/archives/120
// https://kristerw.blogspot.com/2016/02/how-undefined-signed-overflow-enables.html
// https://research.checkpoint.com/2020/optout-compiler-undefined-behavior-optimizations/
// x + c < x -> false
// x + c <= x -> false
// x + c > x -> true
// x + c >= x -> true
// x + y < x -> y < 0
if (!mSettings->isEnabled(Settings::PORTABILITY))
return;
for (const Token *tok = mTokenizer->tokens(); tok; tok = tok->next()) {
if (!Token::Match(tok, "<|<=|>=|>") || !tok->isBinaryOp())
continue;
const Token *lhsTokens[2] = {tok->astOperand1(), tok->astOperand2()};
for (const Token *lhs: lhsTokens) {
std::string cmp = tok->str();
if (lhs == tok->astOperand2())
cmp[0] = (cmp[0] == '<') ? '>' : '<';
if (!Token::Match(lhs, "[+-]") || !lhs->isBinaryOp() || !lhs->valueType() || !lhs->valueType()->isIntegral() || lhs->valueType()->sign != ValueType::Sign::SIGNED)
continue;
const Token *exprTokens[2] = {lhs->astOperand1(), lhs->astOperand2()};
for (const Token *expr: exprTokens) {
if (lhs->str() == "-" && expr == lhs->astOperand2())
continue; // TODO?
if (expr->hasKnownIntValue())
continue;
if (!isSameExpression(mTokenizer->isCPP(),
false,
expr,
lhs->astSibling(),
mSettings->library,
false,
false))
continue;
const Token * const other = expr->astSibling();
// x [+-] c cmp x
if (other->isNumber() && other->getKnownIntValue() > 0) {
bool result;
if (lhs->str() == "+")
result = (cmp == ">" || cmp == ">=");
else
result = (cmp == "<" || cmp == "<=");
integerOverflowOptimisationError(tok, result ? "true" : "false");
}
// x + y cmp x
if (lhs->str() == "+" && other->varId() > 0) {
const std::string result = other->str() + cmp + "0";
integerOverflowOptimisationError(tok, result);
}
// x - y cmp x
if (lhs->str() == "-" && other->varId() > 0) {
std::string cmp2 = cmp;
cmp2[0] = (cmp[0] == '<') ? '>' : '<';
const std::string result = other->str() + cmp2 + "0";
integerOverflowOptimisationError(tok, result);
}
}
}
}
}
void CheckType::integerOverflowOptimisationError(const Token *tok, const std::string &replace)
{
const std::string expr = tok ? tok->expressionString() : "x+c<x";
const std::string errmsg =
"There is a danger that '" + expr + "' will be optimised into '" + replace + "'. Signed integer overflow is undefined behavior.\n"
"There is a danger that '" + expr + "' will be optimised into '" + replace + "'. Your code could work differently depending on what compiler/flags/version/etc is used. Signed integer overflow is undefined behavior and assuming that it will never happen; the result of '" + expr + "' is always '" + replace + "'.";
reportError(tok, Severity::portability, "integerOverflowOptimization", errmsg, CWE190, false);
}
//---------------------------------------------------------------------------
// Checking for sign conversion when operand can be negative
//---------------------------------------------------------------------------

6
lib/checktype.h
View File

@ -54,7 +54,6 @@ public:
CheckType checkType(tokenizer, settings, errorLogger);
checkType.checkTooBigBitwiseShift();
checkType.checkIntegerOverflow();
checkType.checkIntegerOverflowOptimisations();
checkType.checkSignConversion();
checkType.checkLongCast();
checkType.checkFloatToIntegerOverflow();
@ -66,9 +65,6 @@ public:
/** @brief %Check for integer overflow */
void checkIntegerOverflow();
/** @brief Check for overflow code patterns that will be optimized */
void checkIntegerOverflowOptimisations();
/** @brief %Check for dangerous sign conversion */
void checkSignConversion();
@ -85,7 +81,6 @@ private:
void tooBigBitwiseShiftError(const Token *tok, int lhsbits, const ValueFlow::Value &rhsbits);
void tooBigSignedBitwiseShiftError(const Token *tok, int lhsbits, const ValueFlow::Value &rhsbits);
void integerOverflowError(const Token *tok, const ValueFlow::Value &value);
void integerOverflowOptimisationError(const Token *tok, const std::string &replace);
void signConversionError(const Token *tok, const ValueFlow::Value *negativeValue, const bool constvalue);
void longCastAssignError(const Token *tok);
void longCastReturnError(const Token *tok);
@ -113,7 +108,6 @@ private:
return "Type checks\n"
"- bitwise shift by too many bits (only enabled when --platform is used)\n"
"- signed integer overflow (only enabled when --platform is used)\n"
"- expression that can be optimised 'out' because signed integer overflow is undefined behavior.\n"
"- dangerous sign conversion, when signed value can be negative\n"
"- possible loss of information when assigning int result to long variable\n"
"- possible loss of information when returning int result as long return value\n"

71
test/testcondition.cpp
View File

@ -3893,32 +3893,85 @@ private:
check("void f(char *p, unsigned int x) {\n"
" assert((p + x) < p);\n"
"}");
ASSERT_EQUALS("[test.cpp:2]: (warning) Invalid test for overflow '(p+x)<p'. Condition is always false unless there is overflow, and overflow is undefined behaviour.\n", errout.str());
ASSERT_EQUALS("[test.cpp:2]: (warning) Invalid test for overflow '(p+x)<p'; pointer overflow is undefined behavior. Some mainstream compilers remove such overflow tests when optimising the code and assume it's always false.\n", errout.str());
check("void f(char *p, unsigned int x) {\n"
" assert((p + x) >= p);\n"
"}");
ASSERT_EQUALS("[test.cpp:2]: (warning) Invalid test for overflow '(p+x)>=p'. Condition is always true unless there is overflow, and overflow is undefined behaviour.\n", errout.str());
ASSERT_EQUALS("[test.cpp:2]: (warning) Invalid test for overflow '(p+x)>=p'; pointer overflow is undefined behavior. Some mainstream compilers remove such overflow tests when optimising the code and assume it's always true.\n", errout.str());
check("void f(char *p, unsigned int x) {\n"
" assert(p > (p + x));\n"
"}");
ASSERT_EQUALS("[test.cpp:2]: (warning) Invalid test for overflow 'p>(p+x)'. Condition is always false unless there is overflow, and overflow is undefined behaviour.\n", errout.str());
ASSERT_EQUALS("[test.cpp:2]: (warning) Invalid test for overflow 'p>(p+x)'; pointer overflow is undefined behavior. Some mainstream compilers remove such overflow tests when optimising the code and assume it's always false.\n", errout.str());
check("void f(char *p, unsigned int x) {\n"
" assert(p <= (p + x));\n"
"}");
ASSERT_EQUALS("[test.cpp:2]: (warning) Invalid test for overflow 'p<=(p+x)'. Condition is always true unless there is overflow, and overflow is undefined behaviour.\n", errout.str());
check("void f(signed int x) {\n"
" assert(x + 100 < x);\n"
"}");
ASSERT_EQUALS("[test.cpp:2]: (warning) Invalid test for overflow 'x+100<x'. Condition is always false unless there is overflow, and overflow is undefined behaviour.\n", errout.str());
ASSERT_EQUALS("[test.cpp:2]: (warning) Invalid test for overflow 'p<=(p+x)'; pointer overflow is undefined behavior. Some mainstream compilers remove such overflow tests when optimising the code and assume it's always true.\n", errout.str());
check("void f(signed int x) {\n" // unsigned overflow => don't warn
" assert(x + 100U < x);\n"
"}");
ASSERT_EQUALS("", errout.str());
// x + c < x
#define MSG(EXPR, RESULT) "[test.cpp:1]: (warning) Invalid test for overflow '" EXPR "'; signed integer overflow is undefined behavior. Some mainstream compilers remove such overflow tests when optimising the code and assume it's always " RESULT ".\n"
check("int f(int x) { return x + 10 > x; }");
ASSERT_EQUALS(MSG("x+10>x", "true"), errout.str());
check("int f(int x) { return x + 10 >= x; }");
ASSERT_EQUALS(MSG("x+10>=x", "true"), errout.str());
check("int f(int x) { return x + 10 < x; }");
ASSERT_EQUALS(MSG("x+10<x", "false"), errout.str());
check("int f(int x) { return x + 10 <= x; }");
ASSERT_EQUALS(MSG("x+10<=x", "false"), errout.str());
check("int f(int x) { return x - 10 > x; }");
ASSERT_EQUALS(MSG("x-10>x", "false"), errout.str());
check("int f(int x) { return x - 10 >= x; }");
ASSERT_EQUALS(MSG("x-10>=x", "false"), errout.str());
check("int f(int x) { return x - 10 < x; }");
ASSERT_EQUALS(MSG("x-10<x", "true"), errout.str());
check("int f(int x) { return x - 10 <= x; }");
ASSERT_EQUALS(MSG("x-10<=x", "true"), errout.str());
// x + y < x
#undef MSG
#define MSG(EXPR, RESULT) "[test.cpp:1]: (warning) Invalid test for overflow '" EXPR "'; signed integer overflow is undefined behavior. Some mainstream compilers removes handling of overflows when optimising the code and change the code to '" RESULT "'.\n"
check("int f(int x, int y) { return x + y < x; }");
ASSERT_EQUALS(MSG("x+y<x", "y<0"), errout.str());
check("int f(int x, int y) { return x + y <= x; }");
ASSERT_EQUALS(MSG("x+y<=x", "y<=0"), errout.str());
check("int f(int x, int y) { return x + y > x; }");
ASSERT_EQUALS(MSG("x+y>x", "y>0"), errout.str());
check("int f(int x, int y) { return x + y >= x; }");
ASSERT_EQUALS(MSG("x+y>=x", "y>=0"), errout.str());
// x - y < x
check("int f(int x, int y) { return x - y < x; }");
ASSERT_EQUALS(MSG("x-y<x", "y>0"), errout.str());
check("int f(int x, int y) { return x - y <= x; }");
ASSERT_EQUALS(MSG("x-y<=x", "y>=0"), errout.str());
check("int f(int x, int y) { return x - y > x; }");
ASSERT_EQUALS(MSG("x-y>x", "y<0"), errout.str());
check("int f(int x, int y) { return x - y >= x; }");
ASSERT_EQUALS(MSG("x-y>=x", "y<=0"), errout.str());
}
void checkConditionIsAlwaysTrueOrFalseInsideIfWhile() {

58
test/testtype.cpp
View File

@ -35,7 +35,6 @@ private:
void run() OVERRIDE {
TEST_CASE(checkTooBigShift_Unix32);
TEST_CASE(checkIntegerOverflow);
TEST_CASE(checkIntegerOverflowOptimisations);
TEST_CASE(signConversion);
TEST_CASE(longCastAssign);
TEST_CASE(longCastReturn);
@ -249,63 +248,6 @@ private:
ASSERT_EQUALS("", errout.str());
}
void checkIntegerOverflowOptimisations() {
Settings settings;
settings.addEnabled("warning");
// x + c < x
check("int f(int x) { return x + 10 > x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x+10>x' will be optimised into 'true'. Signed integer overflow is undefined behavior.\n", errout.str());
check("int f(int x) { return x + 10 >= x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x+10>=x' will be optimised into 'true'. Signed integer overflow is undefined behavior.\n", errout.str());
check("int f(int x) { return x + 10 < x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x+10<x' will be optimised into 'false'. Signed integer overflow is undefined behavior.\n", errout.str());
check("int f(int x) { return x + 10 <= x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x+10<=x' will be optimised into 'false'. Signed integer overflow is undefined behavior.\n", errout.str());
check("int f(int x) { return x - 10 > x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x-10>x' will be optimised into 'false'. Signed integer overflow is undefined behavior.\n", errout.str());
check("int f(int x) { return x - 10 >= x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x-10>=x' will be optimised into 'false'. Signed integer overflow is undefined behavior.\n", errout.str());
check("int f(int x) { return x - 10 < x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x-10<x' will be optimised into 'true'. Signed integer overflow is undefined behavior.\n", errout.str());
check("int f(int x) { return x - 10 <= x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x-10<=x' will be optimised into 'true'. Signed integer overflow is undefined behavior.\n", errout.str());
// x + y < x
check("int f(int x, int y) { return x + y < x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x+y<x' will be optimised into 'y<0'. Signed integer overflow is undefined behavior.\n", errout.str());
check("int f(int x, int y) { return x + y <= x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x+y<=x' will be optimised into 'y<=0'. Signed integer overflow is undefined behavior.\n", errout.str());
check("int f(int x, int y) { return x + y > x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x+y>x' will be optimised into 'y>0'. Signed integer overflow is undefined behavior.\n", errout.str());
check("int f(int x, int y) { return x + y >= x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x+y>=x' will be optimised into 'y>=0'. Signed integer overflow is undefined behavior.\n", errout.str());
// x - y < x
check("int f(int x, int y) { return x - y < x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x-y<x' will be optimised into 'y>0'. Signed integer overflow is undefined behavior.\n", errout.str());
check("int f(int x, int y) { return x - y <= x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x-y<=x' will be optimised into 'y>=0'. Signed integer overflow is undefined behavior.\n", errout.str());
check("int f(int x, int y) { return x - y > x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x-y>x' will be optimised into 'y<0'. Signed integer overflow is undefined behavior.\n", errout.str());
check("int f(int x, int y) { return x - y >= x; }", &settings);
ASSERT_EQUALS("[test.cpp:1]: (portability) There is a danger that 'x-y>=x' will be optimised into 'y<=0'. Signed integer overflow is undefined behavior.\n", errout.str());
}
void signConversion() {
check("x = -4 * (unsigned)y;");
ASSERT_EQUALS("[test.cpp:1]: (warning) Expression '-4' has a negative value. That is converted to an unsigned value and used in an unsigned calculation.\n", errout.str());