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Fix #15000 Propagate integral cast ranges to condition analysis #8819

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Fix #15000 Propagate integral cast ranges to condition analysis #8819

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18 changes: 18 additions & 0 deletions lib/valueflow.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1087,6 +1087,24 @@ static void valueFlowImpossibleValues(TokenList& tokenList, const Settings& sett
upper.bound = ValueFlow::Value::Bound::Lower;
upper.setImpossible();
setTokenValue(tok, std::move(upper), settings);
} else if (tok->isCast() && tok->valueType() && tok->valueType()->isIntegral() && !tok->valueType()->pointer) {
MathLib::bigint minValue;
MathLib::bigint maxValue;
if (!ValueFlow::getMinMaxValues(tok->valueType(), settings.platform, minValue, maxValue))
continue;

if (minValue > std::numeric_limits<MathLib::bigint>::min()) {
ValueFlow::Value lower{minValue - 1};
lower.bound = ValueFlow::Value::Bound::Upper;
lower.setImpossible();
setTokenValue(tok, std::move(lower), settings);
}
if (maxValue < std::numeric_limits<MathLib::bigint>::max()) {
ValueFlow::Value upper{maxValue + 1};
upper.bound = ValueFlow::Value::Bound::Lower;
upper.setImpossible();
setTokenValue(tok, std::move(upper), settings);
}
} else if (astIsUnsigned(tok) && !astIsPointer(tok)) {
std::vector<MathLib::bigint> minvalue = minUnsignedValue(tok);
if (minvalue.empty())
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18 changes: 13 additions & 5 deletions lib/vf_common.cpp
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Expand Up @@ -46,7 +46,7 @@ namespace ValueFlow
if (!vt || !vt->isIntegral() || vt->pointer)
return false;

std::uint8_t bits;
std::size_t bits;
switch (vt->type) {
case ValueType::Type::BOOL:
bits = 1;
Expand All @@ -66,29 +66,37 @@ namespace ValueFlow
case ValueType::Type::LONGLONG:
bits = platform.long_long_bit;
break;
case ValueType::Type::WCHAR_T:
bits = platform.sizeof_wchar_t * platform.char_bit;
break;
default:
return false;
}

if (bits == 0) {
return false;
}
if (bits == 1) {
minValue = 0;
maxValue = 1;
} else if (bits < 62) {
if (vt->sign == ValueType::Sign::UNSIGNED) {
minValue = 0;
maxValue = (1LL << bits) - 1;
} else {
} else if (vt->sign == ValueType::Sign::SIGNED) {
minValue = -(1LL << (bits - 1));
maxValue = (1LL << (bits - 1)) - 1;
}
} else
return false;
} else if (bits == 64) {
if (vt->sign == ValueType::Sign::UNSIGNED) {
minValue = 0;
maxValue = LLONG_MAX; // todo max unsigned value
} else {
} else if (vt->sign == ValueType::Sign::SIGNED) {
minValue = LLONG_MIN;
maxValue = LLONG_MAX;

@aadanen aadanen Sep 12, 2026 •
edited
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I don't understand how signed 64 bit and unsigned 64 bit have the same max value. Maybe for unsigned you meant ULLONG_MAX?

}
} else
return false;
} else {
return false;
}
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73 changes: 73 additions & 0 deletions test/testcondition.cpp
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Expand Up @@ -6546,6 +6546,79 @@ class TestCondition : public TestFixture {
"[test.cpp:4:13]: (style) Comparing expression of type 'const unsigned int &' against value 4294967295. Condition is always false. [compareValueOutOfTypeRangeError]\n",
errout_str());

check("typedef unsigned int uint32;\n"

@chrchr-github chrchr-github Sep 12, 2026

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There's no need for those typedefs, please use e.g. uint32_t.

"typedef unsigned long long uint64;\n"
"typedef long long sint64;\n"
"void f(uint32 x) {\n"
" uint64 tmp = ((uint64)x) + 1ULL;\n"
" if (tmp > 4294967295ULL)\n"
" tmp = 4294967295ULL;\n"
" if ((((sint64)((uint32)tmp)) - 1LL) < 0LL) {}\n"
" if ((((sint64)((uint32)tmp)) - 1LL) > 4294967295LL) {}\n"
"}\n", settingsUnix64);
ASSERT_EQUALS("[test.cpp:9:41]: (style) Condition '(((long long)((unsigned int)tmp))-1LL)>4294967295LL' is always false [knownConditionTrueFalse]\n",
errout_str());

check("typedef unsigned int uint32;\n"
"typedef unsigned long long uint64;\n"
"typedef long long sint64;\n"
"void f(uint64 tmp) {\n"
" if (tmp > 4294967295ULL)\n"
" tmp = 4294967295ULL;\n"
" if (static_cast<sint64>(static_cast<uint32>(tmp)) - 1LL > 4294967295LL) {}\n"
"}\n", settingsUnix64);
ASSERT_EQUALS("[test.cpp:7:61]: (style) Condition 'static_cast<long long>(static_cast<unsigned int>(tmp))-1LL>4294967295LL' is always false [knownConditionTrueFalse]\n",
errout_str());

// cast directly around variable: both the range-based and the declared-type
// analysis can prove the condition invariant; diag() must prevent duplicates
check("void f(unsigned char c) {\n"
" if ((unsigned char)c > 255) {}\n"
"}\n", settingsUnix64);
ASSERT_EQUALS("[test.cpp:2:28]: (style) Comparing expression of type 'unsigned char' against value 255. Condition is always false. [compareValueOutOfTypeRangeError]\n",
errout_str());

check("void f(unsigned char c) {\n"
" if ((unsigned char)c == 256) {}\n"
"}\n", settingsUnix64);
ASSERT_EQUALS("[test.cpp:2:29]: (style) Comparing expression of type 'unsigned char' against value 256. Condition is always false. [compareValueOutOfTypeRangeError]\n",
errout_str());

check("void f(unsigned int u) {\n"
" if ((unsigned int)u > 4294967295ULL) {}\n"
"}\n", settingsUnix64);
ASSERT_EQUALS("[test.cpp:2:27]: (style) Comparing expression of type 'unsigned int' against value 4294967295. Condition is always false. [compareValueOutOfTypeRangeError]\n",
errout_str());

check("void f(unsigned short s) {\n"
" if ((unsigned int)s > 4294967295ULL) {}\n"
"}\n", settingsUnix64);
ASSERT_EQUALS("[test.cpp:2:27]: (style) Comparing expression of type 'unsigned int' against value 4294967295. Condition is always false. [compareValueOutOfTypeRangeError]\n",
errout_str());

// wchar_t range is derived through ValueType::getSizeOf()
check("void f(wchar_t c) {\n"
" if ((wchar_t)c > 0x7fffffff) {}\n"
"}\n", settingsUnix64);
ASSERT_EQUALS("[test.cpp:2:20]: (style) Condition '(wchar_t)c>0x7fffffff' is always false [knownConditionTrueFalse]\n",
errout_str());

check("void f(unsigned int x) {\n"
" if (-(signed char)x < -129) {}\n"
"}\n", settingsUnix64);
ASSERT_EQUALS("[test.cpp:2:25]: (style) Condition '-(char)x<-129' is always false [knownConditionTrueFalse]\n",
errout_str());

check("void f(int x) {\n"
" if ((x) > 0) {}\n"
"}\n", settingsUnix64);
ASSERT_EQUALS("", errout_str());

check("void f(unsigned int x) {\n"
" if ((unsigned int)x > 0) {}\n"
"}\n", settingsUnix64);
ASSERT_EQUALS("", errout_str());

check("void f() {\n"
" long long ll = 1024 * 1024 * 1024;\n"
" if (ll * 8 < INT_MAX) {}\n"
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16 changes: 16 additions & 0 deletions test/testvalueflow.cpp
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Expand Up @@ -9572,6 +9572,22 @@ class TestValueFlow : public TestFixture {
"}\n";
ASSERT_EQUALS(true, testValueOfXImpossible(code, 3U, "a", -1));
ASSERT_EQUALS(true, testValueOfXImpossible(code, 3U, -1));

const Settings settingsUnix64 = settingsBuilder().platform(Platform::Type::Unix64).build();
code = "void f(unsigned long long x) {\n"
" return (unsigned int)x;\n"
"}\n";
SimpleTokenizer tokenizer(settingsUnix64, *this);
ASSERT(tokenizer.tokenize(code));
const Token* returnTok = Token::findmatch(tokenizer.tokens(), "return (");
ASSERT(returnTok && returnTok->next());
const std::list<ValueFlow::Value>& castValues = returnTok->next()->values();
ASSERT(std::any_of(castValues.cbegin(), castValues.cend(), [](const ValueFlow::Value& value) {
return value.isImpossible() && value.intvalue == -1;
}));
ASSERT(std::any_of(castValues.cbegin(), castValues.cend(), [](const ValueFlow::Value& value) {
return value.isImpossible() && value.intvalue == 4294967296;
}));
}

void valueFlowImpossibleIncDec()
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