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Warn when shifting a negative value, it is UB. (#4931)

This commit is contained in:
Daniel Marjamäki 2015-11-29 16:28:55 +01:00
parent 8a9e068129
commit 4fa888ec44
3 changed files with 44 additions and 41 deletions
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19
lib/checkother.cpp
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@ -2177,11 +2177,7 @@ void CheckOther::redundantCopyError(const Token *tok,const std::string& varname)
void CheckOther::checkNegativeBitwiseShift() void CheckOther::checkNegativeBitwiseShift()
{ {
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase(); for (const Token* tok = _tokenizer->tokens(); tok; tok = tok->next()) {
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
const Scope * scope = symbolDatabase->functionScopes[i];
for (const Token* tok = scope->classStart->next(); tok != scope->classEnd; tok = tok->next()) {
if (tok->str() != "<<" && tok->str() != ">>") if (tok->str() != "<<" && tok->str() != ">>")
continue; continue;
@ -2214,16 +2210,19 @@ void CheckOther::checkNegativeBitwiseShift()
continue; continue;
// Get negative rhs value. preferably a value which doesn't have 'condition'. // Get negative rhs value. preferably a value which doesn't have 'condition'.
const ValueFlow::Value *value = tok->astOperand2()->getValueLE(-1LL, _settings); if (tok->astOperand1()->getValueLE(-1LL, _settings))
if (value) negativeBitwiseShiftError(tok, 1);
negativeBitwiseShiftError(tok); else if (tok->astOperand2()->getValueLE(-1LL, _settings))
} negativeBitwiseShiftError(tok, 2);
} }
} }
void CheckOther::negativeBitwiseShiftError(const Token *tok) void CheckOther::negativeBitwiseShiftError(const Token *tok, int op)
{ {
if (op == 1) // LHS
reportError(tok, Severity::error, "shiftNegative", "Shifting a negative value is undefined behaviour");
else // RHS
reportError(tok, Severity::error, "shiftNegative", "Shifting by a negative value is undefined behaviour"); reportError(tok, Severity::error, "shiftNegative", "Shifting by a negative value is undefined behaviour");
} }

4
lib/checkother.h
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@ -243,7 +243,7 @@ private:
void unsignedPositiveError(const Token *tok, const std::string &varname, bool inconclusive); void unsignedPositiveError(const Token *tok, const std::string &varname, bool inconclusive);
void pointerPositiveError(const Token *tok, bool inconclusive); void pointerPositiveError(const Token *tok, bool inconclusive);
void SuspiciousSemicolonError(const Token *tok); void SuspiciousSemicolonError(const Token *tok);
void negativeBitwiseShiftError(const Token *tok); void negativeBitwiseShiftError(const Token *tok, int op);
void redundantCopyError(const Token *tok, const std::string &varname); void redundantCopyError(const Token *tok, const std::string &varname);
void incompleteArrayFillError(const Token* tok, const std::string& buffer, const std::string& function, bool boolean); void incompleteArrayFillError(const Token* tok, const std::string& buffer, const std::string& function, bool boolean);
void varFuncNullUBError(const Token *tok); void varFuncNullUBError(const Token *tok);
@ -260,7 +260,7 @@ private:
c.zerodivcondError(0,0,false); c.zerodivcondError(0,0,false);
c.misusedScopeObjectError(NULL, "varname"); c.misusedScopeObjectError(NULL, "varname");
c.invalidPointerCastError(0, "float", "double", false); c.invalidPointerCastError(0, "float", "double", false);
c.negativeBitwiseShiftError(0); c.negativeBitwiseShiftError(0,1);
c.checkPipeParameterSizeError(0, "varname", "dimension"); c.checkPipeParameterSizeError(0, "varname", "dimension");
c.raceAfterInterlockedDecrementError(0); c.raceAfterInterlockedDecrementError(0);

4
test/testother.cpp
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@ -4774,6 +4774,10 @@ private:
check("x = y ? z << $-1 : 0;\n"); check("x = y ? z << $-1 : 0;\n");
ASSERT_EQUALS("", errout.str()); ASSERT_EQUALS("", errout.str());
// Negative LHS
check("const int x = -1 >> 2;");
ASSERT_EQUALS("[test.cpp:1]: (error) Shifting a negative value is undefined behaviour\n", errout.str());
} }
void incompleteArrayFill() { void incompleteArrayFill() {