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Fix 13930: False positive: valueflow and other variable #7827

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Fix 13930: False positive: valueflow and other variable #7827

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ea3b82e
Use new pm
pfultz2 Jul 8, 2025
453aae2
Merge branch 'main' into program-memory-use-new-pm-assign
pfultz2 Jul 22, 2025
2d61478
Add ifdef
pfultz2 Aug 8, 2025
417e0a7
Add ifdef and prints
pfultz2 Aug 18, 2025
d7ddf77
Fix unit tests
pfultz2 Sep 15, 2025
19de481
Format
pfultz2 Sep 15, 2025
a107e85
Add test
pfultz2 Sep 16, 2025
feb4cf4
Remove comments
pfultz2 Sep 16, 2025
7b55579
Remove debug print
pfultz2 Sep 16, 2025
c57b41f
Add comment
pfultz2 Sep 22, 2025
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25 changes: 16 additions & 9 deletions lib/programmemory.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -205,14 +205,19 @@ bool ProgramMemory::empty() const
}

// NOLINTNEXTLINE(performance-unnecessary-value-param) - technically correct but we are moving the given values
void ProgramMemory::replace(ProgramMemory pm)
void ProgramMemory::replace(ProgramMemory pm, bool skipUnknown)
{
if (pm.empty())
return;

copyOnWrite();

for (auto&& p : (*pm.mValues)) {
if (skipUnknown) {
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Why is this called skipUnknown? It seems to skip uninit values.

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We set it to uninit value when the value is unknown:

https://github.com/danmar/cppcheck/blob/main/lib/vfvalue.h#L59
https://github.com/danmar/cppcheck/blob/main/lib/programmemory.cpp#L163

auto it = mValues->find(p.first);
if (it != mValues->end() && it->second.isUninitValue())
continue;
}
(*mValues)[p.first] = std::move(p.second);
}
}
Expand Down Expand Up @@ -405,7 +410,8 @@ static void fillProgramMemoryFromAssignments(ProgramMemory& pm, const Token* tok
if (!setvar) {
if (!pm.hasValue(vartok->exprId())) {
const Token* valuetok = tok2->astOperand2();
pm.setValue(vartok, execute(valuetok, pm, settings));
ProgramMemory local = state;
pm.setValue(vartok, execute(valuetok, local, settings));
}
}
} else if (tok2->exprId() > 0 && Token::Match(tok2, ".|(|[|*|%var%") && !pm.hasValue(tok2->exprId()) &&
Expand Down Expand Up @@ -476,7 +482,7 @@ void ProgramMemoryState::replace(ProgramMemory pm, const Token* origin)
if (origin)
for (const auto& p : pm)
origins[p.first.getExpressionId()] = origin;
state.replace(std::move(pm));
state.replace(std::move(pm), /*skipUnknown*/ true);
}

static void addVars(ProgramMemory& pm, const ProgramMemory::Map& vars)
Expand All @@ -489,13 +495,14 @@ static void addVars(ProgramMemory& pm, const ProgramMemory::Map& vars)

void ProgramMemoryState::addState(const Token* tok, const ProgramMemory::Map& vars)
{
ProgramMemory pm = state;
addVars(pm, vars);
fillProgramMemoryFromConditions(pm, tok, settings);
ProgramMemory local = pm;
ProgramMemory local = state;
addVars(local, vars);
fillProgramMemoryFromConditions(local, tok, settings);
ProgramMemory pm;
fillProgramMemoryFromAssignments(pm, tok, settings, local, vars);
addVars(pm, vars);
replace(std::move(pm), tok);
local.replace(std::move(pm));
addVars(local, vars);
replace(std::move(local), tok);
}

void ProgramMemoryState::assume(const Token* tok, bool b, bool isEmpty)
Expand Down
2 changes: 1 addition & 1 deletion lib/programmemory.h
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Expand Up @@ -130,7 +130,7 @@ struct CPPCHECKLIB ProgramMemory {

bool empty() const;

void replace(ProgramMemory pm);
void replace(ProgramMemory pm, bool skipUnknown = false);

Map::const_iterator begin() const {
return mValues->cbegin();
Expand Down
17 changes: 17 additions & 0 deletions test/testuninitvar.cpp
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Expand Up @@ -6588,6 +6588,23 @@ class TestUninitVar : public TestFixture {
" return c.front();\n"
"}\n");
ASSERT_EQUALS("[test.cpp:8:12]: (error) Uninitialized variable: c [uninitvar]\n", errout_str());

// #13930
valueFlowUninit("extern int32_t g_items[10U];\n"
"uint16_t write_item(uint8_t n);\n"
"uint16_t write_item(uint8_t n) {\n"
" int32_t *p_item = NULL;\n"
" uint16_t ret;\n"
" ret = 0U;\n"
" if (n < 10U)\n"
" p_item = &g_items[n];\n"
" else\n"
" ret = 1U;\n"
" if (ret == 0U) \n"
" *p_item = 5;\n"
" return ret;\n"
"}\n");
ASSERT_EQUALS("", errout_str());
}

void valueFlowUninitBreak() { // Do not show duplicate warnings about the same uninitialized value
Expand Down