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Partial fix for #15048: Inconsistent error severity for nullpointer #8961

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Partial fix for #15048: Inconsistent error severity for nullpointer #8961

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b3e95d3
Update checknullpointer.cpp
chrchr-github Oct 26, 2026
3aa29a1
Update testnullpointer.cpp
chrchr-github Oct 26, 2026
5394c1d
Update checknullpointer.cpp [skip ci]
chrchr-github Oct 27, 2026
ddb3eaf
Update testnullpointer.cpp
chrchr-github Oct 27, 2026
09eea1c
Update testnullpointer.cpp
chrchr-github Oct 27, 2026
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4 changes: 2 additions & 2 deletions lib/checknullpointer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -454,7 +454,7 @@ void CheckNullPointerImpl::nullPointerError(const Token *tok, const std::string
} else if (value->defaultArg) {
reportError(std::move(errorPath), Severity::warning, "nullPointerDefaultArg", errmsgdefarg, CWE_NULL_POINTER_DEREFERENCE, inconclusive || value->isInconclusive() ? Certainty::inconclusive : Certainty::normal);
} else {
std::string errmsg = std::string(value->isKnown() ? "Null" : "Possible null") + " pointer dereference";
std::string errmsg = std::string(value->isKnown() && !value->conditional ? "Null" : "Possible null") + " pointer dereference";

std::string id = "nullPointer";
if (value->unknownFunctionReturn == ValueFlow::Value::UnknownFunctionReturn::outOfMemory) {
Expand All @@ -470,7 +470,7 @@ void CheckNullPointerImpl::nullPointerError(const Token *tok, const std::string
errmsg = "$symbol:" + varname + '\n' + errmsg + ": $symbol";

reportError(std::move(errorPath),
value->isKnown() ? Severity::error : Severity::warning,
value->isKnown() && !value->conditional ? Severity::error : Severity::warning,

@dmcppcheck dmcppcheck Oct 27, 2026

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AI review

conditional is only set by makeConditional() when the forward analyzer assumes an if condition. So the severity now depends on how the code is written, not on how certain the value is:

int f(bool b) { int* p = nullptr; if (b) { return *p; } return 0; }    // warning
int g(bool b) { int* p = nullptr; while (b) { return *p; } return 0; } // error
int h(bool b) { int* p = nullptr; return b ? *p : 0; }                 // error
int k(bool b) { int* p = nullptr; return b && *p; }                    // error

The message on line 457 is still chosen from isKnown() alone, so these warnings say "Null pointer dereference" instead of "Possible null pointer dereference". The same id and the same text now come at two severities.

In all of these cases p is null on every path that reaches the dereference. If the goal is consistent severity, it should probably not depend on the conditional flag.

id.c_str(),
errmsg,
CWE_NULL_POINTER_DEREFERENCE, inconclusive || value->isInconclusive() ? Certainty::inconclusive : Certainty::normal);
Expand Down
28 changes: 23 additions & 5 deletions test/testnullpointer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -173,6 +173,7 @@ class TestNullPointer : public TestFixture {
TEST_CASE(nullpointerSmartPointer);
TEST_CASE(nullpointerOutOfMemory);
TEST_CASE(nullpointerOutOfResources);
TEST_CASE(nullpointerErrorPath);
TEST_CASE(functioncall);
TEST_CASE(functioncalllibrary); // use Library to parse function call
TEST_CASE(functioncallDefaultArguments);
Expand Down Expand Up @@ -2488,7 +2489,7 @@ class TestNullPointer : public TestFixture {
" *p = 0;\n"
" }\n"
"}\n");
ASSERT_EQUALS("[test.cpp:4:10]: (error) Null pointer dereference: p [nullPointer]\n", errout_str());
ASSERT_EQUALS("[test.cpp:4:10]: (warning) Possible null pointer dereference: p [nullPointer]\n", errout_str());
}

void nullpointer78() // #7802
Expand Down Expand Up @@ -4100,10 +4101,10 @@ class TestNullPointer : public TestFixture {
" foo(p == s2);\n"
" foo(p == s3);\n"
"}\n", dinit(CheckOptions, $.inconclusive = true));
ASSERT_EQUALS("[test.cpp:4:15]: (error) Null pointer dereference: p [nullPointer]\n"
"[test.cpp:5:15]: (error) Null pointer dereference: p [nullPointer]\n"
"[test.cpp:7:9]: (error) Null pointer dereference: p [nullPointer]\n"
"[test.cpp:8:9]: (error) Null pointer dereference: p [nullPointer]\n", errout_str());
ASSERT_EQUALS("[test.cpp:4:15]: (warning) Possible null pointer dereference: p [nullPointer]\n"
"[test.cpp:5:15]: (warning) Possible null pointer dereference: p [nullPointer]\n"
"[test.cpp:7:9]: (warning) Possible null pointer dereference: p [nullPointer]\n"
"[test.cpp:8:9]: (warning) Possible null pointer dereference: p [nullPointer]\n", errout_str());

check("void f(std::string s1, const std::string& s2, const std::string* s3) {\n"
" void* p = 0;\n"
Expand Down Expand Up @@ -4586,6 +4587,23 @@ class TestNullPointer : public TestFixture {
errout_str());
}

void nullpointerErrorPath() {
setMultiline();

check("int f(bool b) {\n"
" int* p = nullptr;\n"
" if (b)\n"
" return 0;\n"
" return *p;\n"
"}\n");
ASSERT_EQUALS(
"[test.cpp:5:13]: warning: Possible null pointer dereference: p [nullPointer]\n"
"[test.cpp:2:14]: note: Assignment 'p=nullptr', assigned value is 0\n"
"[test.cpp:3:9]: note: Assuming condition is false\n"
"[test.cpp:5:13]: note: Null pointer dereference\n",
errout_str());
}

void functioncalllibrary() {
SimpleTokenizer tokenizer(settingsDefault,*this,false);
const char code[] = "void f() { int a,b,c; x(a,b,c); }\n";
Expand Down
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