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Fix #13148 FN: constStatement (static_cast<void>(integer|nullptr|NULL)) #8694

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Fix #13148 FN: constStatement (static_cast<void>(integer|nullptr|NULL)) #8694

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84bf3bf
Update checkother.cpp
chrchr-github Jul 3, 2026
256f3c3
Update testincompletestatement.cpp
chrchr-github Jul 3, 2026
b4c8be1
Fix
web-flow Jul 3, 2026
6fb5cb0
Update cfg.c
chrchr-github Jul 3, 2026
1f2bbf5
Adjust error messages
web-flow Jul 12, 2026
e0c06b3
Fix
web-flow Jul 12, 2026
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38 changes: 13 additions & 25 deletions lib/checkother.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2323,18 +2323,12 @@ static bool isConstStatement(const Token *tok, const Library& library, bool plat

static bool isVoidStmt(const Token *tok)
{
if (Token::simpleMatch(tok, "( void"))
if (Token::simpleMatch(tok, "( void") && !(tok->astOperand1() && (tok->astOperand1()->isLiteral() || isNullOperand(tok->astOperand1()))))
return true;
if (isCPPCast(tok) && tok->astOperand1() && Token::Match(tok->astOperand1()->next(), "< void *| >"))
if (isCPPCast(tok) && tok->astOperand1() && Token::Match(tok->astOperand1()->next(), "< void *| >") &&
!(tok->astOperand2() && (tok->astOperand2()->isLiteral() || isNullOperand(tok->astOperand2()))))
return true;
const Token *tok2 = tok;
while (tok2->astOperand1())
tok2 = tok2->astOperand1();
if (Token::simpleMatch(tok2->previous(), ")") && Token::simpleMatch(tok2->linkAt(-1), "( void"))
return true;
if (Token::simpleMatch(tok2, "( void"))
return true;
return Token::Match(tok2->previous(), "delete|throw|return");
return false;
}

static bool isConstTop(const Token *tok)
Expand Down Expand Up @@ -2425,37 +2419,31 @@ void CheckOtherImpl::checkIncompleteStatement()

void CheckOtherImpl::constStatementError(const Token *tok, const std::string &type, bool inconclusive)
{
const Token *valueTok = tok;
while (valueTok && valueTok->isCast())
valueTok = valueTok->astOperand2() ? valueTok->astOperand2() : valueTok->astOperand1();

std::string msg;
if (Token::simpleMatch(tok, "=="))
msg = "Found suspicious equality comparison. Did you intend to assign a value instead?";
else if (Token::Match(tok, ",|!|~|%cop%"))
msg = "Found suspicious operator '" + tok->str() + "', result is not used.";
else if (Token::Match(tok, "%var%"))
msg = "Unused variable value '" + tok->str() + "'";
else if (isConstant(valueTok)) {
else if (isConstant(tok)) {
std::string typeStr("string");
if (valueTok->isNumber())
if (tok->isNumber())
typeStr = "numeric";
else if (valueTok->isBoolean())
else if (tok->isBoolean())
typeStr = "bool";
else if (valueTok->tokType() == Token::eChar)
else if (tok->tokType() == Token::eChar)
typeStr = "character";
else if (isNullOperand(valueTok))
typeStr = "NULL";
else if (valueTok->isEnumerator())
else if (isNullOperand(tok))
typeStr = "null";
else if (tok->isEnumerator())
typeStr = "enumerator";
msg = "Redundant code: Found a statement that begins with " + typeStr + " constant.";
}
else if (!tok)
msg = "Redundant code: Found a statement that begins with " + type + " constant.";
else if (tok->isCast() && tok->tokType() == Token::Type::eExtendedOp) {
msg = "Redundant code: Found unused cast ";
msg += valueTok ? "of expression '" + valueTok->expressionString() + "'." : "expression.";
}
else if (tok->isCast() && tok->tokType() == Token::Type::eExtendedOp)
msg = "Redundant code: Found unused cast in expression '" + tok->expressionString() + "'.";
else if (tok->str() == "?" && tok->tokType() == Token::Type::eExtendedOp)
msg = "Redundant code: Found unused result of ternary operator.";
else if (tok->str() == "." && tok->tokType() == Token::Type::eOther)
Expand Down
4 changes: 2 additions & 2 deletions test/cli/proj-inline-suppress/cfg.c
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Expand Up @@ -2,9 +2,9 @@ void f()
{
#if DEF_1
// cppcheck-suppress id
(void)0;
;
#endif

// cppcheck-suppress id
(void)0;
;
}
40 changes: 28 additions & 12 deletions test/testincompletestatement.cpp
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Expand Up @@ -180,9 +180,25 @@ class TestIncompleteStatement : public TestFixture {
}

void void0() { // #6327
check("void f() { (void*)0; }");
check("#define assert(x) ((void)0)\n"
"void f(int* p) {\n"
" assert(p);\n"
"}\n");
ASSERT_EQUALS("", errout_str());

check("void f() { (void*)0; }");
ASSERT_EQUALS("[test.cpp:1:12]: (warning) Redundant code: Found unused cast in expression '(void*)0'. [constStatement]\n", errout_str());

check("void f() {\n" // #13148
" static_cast<void>(1);\n"
" static_cast<void>(nullptr);\n"
" (void)NULL;\n"
"}\n");
ASSERT_EQUALS("[test.cpp:2:22]: (warning) Redundant code: Found unused cast in expression 'static_cast<void>(1)'. [constStatement]\n"
"[test.cpp:3:22]: (warning) Redundant code: Found unused cast in expression 'static_cast<void>(nullptr)'. [constStatement]\n"
"[test.cpp:4:5]: (warning) Redundant code: Found unused cast in expression '(void)NULL'. [constStatement]\n",
errout_str());

check("#define X 0\n"
"void f() { X; }");
ASSERT_EQUALS("", errout_str());
Expand Down Expand Up @@ -432,11 +448,11 @@ class TestIncompleteStatement : public TestFixture {
"}\n", dinit(CheckOptions, $.inconclusive = true));
ASSERT_EQUALS("[test.cpp:2:5]: (warning) Redundant code: Found a statement that begins with numeric constant. [constStatement]\n"
"[test.cpp:3:6]: (warning) Redundant code: Found a statement that begins with numeric constant. [constStatement]\n"
"[test.cpp:4:5]: (warning) Redundant code: Found a statement that begins with numeric constant. [constStatement]\n"
"[test.cpp:5:6]: (warning) Redundant code: Found a statement that begins with numeric constant. [constStatement]\n"
"[test.cpp:4:5]: (warning) Redundant code: Found unused cast in expression '(char)1'. [constStatement]\n"
"[test.cpp:5:6]: (warning) Redundant code: Found unused cast in expression '(char)1'. [constStatement]\n"
"[test.cpp:6:5]: (warning, inconclusive) Found suspicious operator '!', result is not used. [constStatement]\n"
"[test.cpp:7:6]: (warning, inconclusive) Found suspicious operator '!', result is not used. [constStatement]\n"
"[test.cpp:8:5]: (warning) Redundant code: Found unused cast of expression '!x'. [constStatement]\n"
"[test.cpp:8:5]: (warning) Redundant code: Found unused cast in expression '(unsigned int)!x'. [constStatement]\n"
"[test.cpp:9:5]: (warning, inconclusive) Found suspicious operator '~', result is not used. [constStatement]\n",
errout_str());

Expand All @@ -447,7 +463,7 @@ class TestIncompleteStatement : public TestFixture {
ASSERT_EQUALS("", errout_str());

check("void f(int x) { static_cast<unsigned>(x); }");
ASSERT_EQUALS("[test.cpp:1:38]: (warning) Redundant code: Found unused cast of expression 'x'. [constStatement]\n", errout_str());
ASSERT_EQUALS("[test.cpp:1:38]: (warning) Redundant code: Found unused cast in expression 'static_cast<unsigned int>(x)'. [constStatement]\n", errout_str());

check("void f(int x, int* p) {\n"
" static_cast<void>(x);\n"
Expand All @@ -465,9 +481,9 @@ class TestIncompleteStatement : public TestFixture {
" static_cast<float>((char)i);\n"
" (char)static_cast<float>(i);\n"
"}\n");
ASSERT_EQUALS("[test.cpp:2:5]: (warning) Redundant code: Found unused cast of expression 'i'. [constStatement]\n"
"[test.cpp:3:23]: (warning) Redundant code: Found unused cast of expression 'i'. [constStatement]\n"
"[test.cpp:4:5]: (warning) Redundant code: Found unused cast of expression 'i'. [constStatement]\n",
ASSERT_EQUALS("[test.cpp:2:5]: (warning) Redundant code: Found unused cast in expression '(float)(char)i'. [constStatement]\n"
"[test.cpp:3:23]: (warning) Redundant code: Found unused cast in expression 'static_cast<float>((char)i)'. [constStatement]\n"
"[test.cpp:4:5]: (warning) Redundant code: Found unused cast in expression '(char)static_cast<float>(i)'. [constStatement]\n",
errout_str());

check("namespace M {\n"
Expand All @@ -476,7 +492,7 @@ class TestIncompleteStatement : public TestFixture {
"void f(int i) {\n"
" (M::N::T)i;\n"
"}\n");
ASSERT_EQUALS("[test.cpp:5:5]: (warning) Redundant code: Found unused cast of expression 'i'. [constStatement]\n", errout_str());
ASSERT_EQUALS("[test.cpp:5:5]: (warning) Redundant code: Found unused cast in expression '(char)i'. [constStatement]\n", errout_str());

check("void f(int (g)(int a, int b)) {\n" // #10873
" int p = 0, q = 1;\n"
Expand Down Expand Up @@ -528,7 +544,7 @@ class TestIncompleteStatement : public TestFixture {
" for (L\"y\"; ;) {}\n"
"}\n");
ASSERT_EQUALS("[test.cpp:2:10]: (warning) Unused variable value 'i' [constStatement]\n"
"[test.cpp:3:10]: (warning) Redundant code: Found unused cast of expression 'i'. [constStatement]\n"
"[test.cpp:3:10]: (warning) Redundant code: Found unused cast in expression '(long)i'. [constStatement]\n"
"[test.cpp:4:10]: (warning) Redundant code: Found a statement that begins with numeric constant. [constStatement]\n"
"[test.cpp:5:10]: (warning) Redundant code: Found a statement that begins with bool constant. [constStatement]\n"
"[test.cpp:6:10]: (warning) Redundant code: Found a statement that begins with character constant. [constStatement]\n"
Expand Down Expand Up @@ -696,8 +712,8 @@ class TestIncompleteStatement : public TestFixture {
" NULL;\n"
" nullptr;\n"
"}\n");
ASSERT_EQUALS("[test.cpp:2:5]: (warning) Redundant code: Found a statement that begins with NULL constant. [constStatement]\n"
"[test.cpp:3:5]: (warning) Redundant code: Found a statement that begins with NULL constant. [constStatement]\n",
ASSERT_EQUALS("[test.cpp:2:5]: (warning) Redundant code: Found a statement that begins with null constant. [constStatement]\n"
"[test.cpp:3:5]: (warning) Redundant code: Found a statement that begins with null constant. [constStatement]\n",
errout_str());

check("struct S { int i; };\n" // #6504
Expand Down
7 changes: 5 additions & 2 deletions test/testother.cpp
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Expand Up @@ -3914,7 +3914,9 @@ class TestOther : public TestFixture {
" (void)(true);\n"
" if (r) {}\n"
"}\n");
ASSERT_EQUALS("[test.cpp:1:13]: (style) Parameter 'r' can be declared as reference to const [constParameterReference]\n", errout_str());
ASSERT_EQUALS("[test.cpp:2:5]: (warning) Redundant code: Found unused cast in expression '(void)(true)'. [constStatement]\n"
"[test.cpp:1:13]: (style) Parameter 'r' can be declared as reference to const [constParameterReference]\n",
errout_str());

check("struct S { void f(int&); };\n" // #12216
"void g(S& s, int& r, void (S::* p2m)(int&)) {\n"
Expand Down Expand Up @@ -7012,7 +7014,8 @@ class TestOther : public TestFixture {
" std::pair<int, int>(1, 2);\n"
" (void)0;\n"
"}\n");
ASSERT_EQUALS("[test.cpp:2:10]: (style) Instance of 'std::string' object is destroyed immediately. [unusedScopedObject]\n"
ASSERT_EQUALS("[test.cpp:5:5]: (warning) Redundant code: Found unused cast in expression '(void)0'. [constStatement]\n"
"[test.cpp:2:10]: (style) Instance of 'std::string' object is destroyed immediately. [unusedScopedObject]\n"
"[test.cpp:3:10]: (style) Instance of 'std::string' object is destroyed immediately. [unusedScopedObject]\n"
"[test.cpp:4:10]: (style) Instance of 'std::pair' object is destroyed immediately. [unusedScopedObject]\n",
errout_str());
Expand Down
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