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New check: Recommend expm1, log1p, erfc (#5392)

This commit is contained in:
PKEuS 2014-09-07 11:37:58 +02:00
parent 7142edf03e
commit ff4fc6a234
3 changed files with 59 additions and 1 deletions
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19
lib/checkother.cpp
View File

@ -1892,6 +1892,8 @@ void CheckOther::nanInArithmeticExpressionError(const Token *tok)
//---------------------------------------------------------------------------
void CheckOther::checkMathFunctions()
{
bool styleC99 = _settings->isEnabled("style") && _settings->standards.c != Standards::C89 && _settings->standards.cpp != Standards::CPP03;
const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
const std::size_t functions = symbolDatabase->functionScopes.size();
for (std::size_t i = 0; i < functions; ++i) {
@ -1943,6 +1945,18 @@ void CheckOther::checkMathFunctions()
MathLib::isNegative(tok->strAt(4))) {
mathfunctionCallWarning(tok, 2);
}
if (styleC99) {
if (Token::Match(tok, "%num% - erf (") && MathLib::toDoubleNumber(tok->str()) == 1.0 && tok->next()->astOperand2() == tok->tokAt(3)) {
mathfunctionCallWarning(tok, "1 - erf(x)", "erfc(x)");
} else if (Token::simpleMatch(tok, "exp (") && Token::Match(tok->linkAt(1), ") - %num%") && MathLib::toDoubleNumber(tok->linkAt(1)->strAt(2)) == 1.0 && tok->linkAt(1)->next()->astOperand1() == tok->next()) {
mathfunctionCallWarning(tok, "exp(x) - 1", "expm1(x)");
} else if (Token::Match(tok, "log (") && tok->next()->astOperand2()) {
const Token* plus = tok->next()->astOperand2();
if (plus->str() == "+" && ((plus->astOperand1() && MathLib::toDoubleNumber(plus->astOperand1()->str()) == 1.0) || (plus->astOperand2() && MathLib::toDoubleNumber(plus->astOperand2()->str()) == 1.0)))
mathfunctionCallWarning(tok, "log(1 + x)", "log10(x)");
}
}
}
}
}
@ -1958,6 +1972,11 @@ void CheckOther::mathfunctionCallWarning(const Token *tok, const unsigned int nu
reportError(tok, Severity::warning, "wrongmathcall", "Passing value '#' to #() leads to implementation-defined result.");
}
void CheckOther::mathfunctionCallWarning(const Token *tok, const std::string& oldexp, const std::string& newexp)
{
reportError(tok, Severity::style, "unpreciseMathCall", "Expression '" + oldexp + "' can be replaced by '" + newexp + "' to avoid loss of precision.");
}
//---------------------------------------------------------------------------
// Creating instance of clases which are destroyed immediately
//---------------------------------------------------------------------------

5
lib/checkother.h
View File

@ -258,6 +258,7 @@ private:
void zerodivcondError(const Token *tokcond, const Token *tokdiv, bool inconclusive);
void nanInArithmeticExpressionError(const Token *tok);
void mathfunctionCallWarning(const Token *tok, const unsigned int numParam = 1);
void mathfunctionCallWarning(const Token *tok, const std::string& oldexp, const std::string& newexp);
void redundantAssignmentError(const Token *tok1, const Token* tok2, const std::string& var, bool inconclusive);
void redundantAssignmentInSwitchError(const Token *tok1, const Token *tok2, const std::string &var);
void redundantCopyError(const Token *tok1, const Token* tok2, const std::string& var);
@ -326,6 +327,7 @@ private:
c.suspiciousEqualityComparisonError(0);
c.selfAssignmentError(0, "varname");
c.mathfunctionCallWarning(0);
c.mathfunctionCallWarning(0, "1 - erf(x)", "erfc(x)");
c.memsetZeroBytesError(0, "varname");
c.memsetFloatError(0, "varname");
c.memsetValueOutOfRangeError(0, "varname");
@ -405,7 +407,8 @@ private:
"* redundant get and set function of user id (--std=posix).\n"
"* Passing NULL pointer to function with variable number of arguments leads to UB on some platforms.\n"
"* NaN (not a number) value used in arithmetic expression.\n"
"* comma in return statement (the comma can easily be misread as a semicolon).\n";
"* comma in return statement (the comma can easily be misread as a semicolon).\n"
"* prefer erfc, expm1 or log1p to avoid loss of precision.\n";
}
};
/// @}

36
test/testother.cpp
View File

@ -88,6 +88,7 @@ private:
TEST_CASE(mathfunctionCall_asin);
TEST_CASE(mathfunctionCall_pow);
TEST_CASE(mathfunctionCall_atan2);
TEST_CASE(mathfunctionCall_precision);
TEST_CASE(switchRedundantAssignmentTest);
TEST_CASE(switchRedundantOperationTest);
@ -1689,6 +1690,41 @@ private:
ASSERT_EQUALS("", errout.str());
}
void mathfunctionCall_precision() {
check("void foo() {\n"
" print(exp(x) - 1);\n"
" print(log(1 + x));\n"
" print(1 - erf(x));\n"
"}");
ASSERT_EQUALS("[test.cpp:2]: (style) Expression 'exp(x) - 1' can be replaced by 'expm1(x)' to avoid loss of precision.\n"
"[test.cpp:3]: (style) Expression 'log(1 + x)' can be replaced by 'log10(x)' to avoid loss of precision.\n"
"[test.cpp:4]: (style) Expression '1 - erf(x)' can be replaced by 'erfc(x)' to avoid loss of precision.\n", errout.str());
check("void foo() {\n"
" print(exp(x) - 1.0);\n"
" print(log(1.0 + x));\n"
" print(1.0 - erf(x));\n"
"}");
ASSERT_EQUALS("[test.cpp:2]: (style) Expression 'exp(x) - 1' can be replaced by 'expm1(x)' to avoid loss of precision.\n"
"[test.cpp:3]: (style) Expression 'log(1 + x)' can be replaced by 'log10(x)' to avoid loss of precision.\n"
"[test.cpp:4]: (style) Expression '1 - erf(x)' can be replaced by 'erfc(x)' to avoid loss of precision.\n", errout.str());
check("void foo() {\n"
" print(exp(3 + x*f(a)) - 1);\n"
" print(log(x*4 + 1));\n"
" print(1 - erf(34*x + f(x) - c));\n"
"}");
ASSERT_EQUALS("[test.cpp:2]: (style) Expression 'exp(x) - 1' can be replaced by 'expm1(x)' to avoid loss of precision.\n"
"[test.cpp:3]: (style) Expression 'log(1 + x)' can be replaced by 'log10(x)' to avoid loss of precision.\n"
"[test.cpp:4]: (style) Expression '1 - erf(x)' can be replaced by 'erfc(x)' to avoid loss of precision.\n", errout.str());
check("void foo() {\n"
" print(2*exp(x) - 1);\n"
" print(1 - erf(x)/2.0);\n"
"}");
ASSERT_EQUALS("", errout.str());
}
void switchRedundantAssignmentTest() {
check("void foo()\n"