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Fix #14195 Show warning when main() throws an exception #7887

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Merged
chrchr-github merged 10 commits into from
Oct 27, 2025
Merged

Fix #14195 Show warning when main() throws an exception #7887

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f6f8dc1
Update checkexceptionsafety.cpp
chrchr-github Oct 14, 2025
260532b
Update checkexceptionsafety.h
chrchr-github Oct 14, 2025
999350f
Update testexceptionsafety.cpp
chrchr-github Oct 14, 2025
a5e9287
Update checkexceptionsafety.cpp
chrchr-github Oct 14, 2025
e369865
Format
chrchr-github Oct 14, 2025
83217b8
Format
chrchr-github Oct 14, 2025
8fe787f
Update checkexceptionsafety.cpp
chrchr-github Oct 20, 2025
3269329
Update checkexceptionsafety.cpp
chrchr-github Oct 20, 2025
8ab4575
Add test
web-flow Oct 27, 2025
2133a5d
Improve error message
web-flow Oct 27, 2025
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34 changes: 19 additions & 15 deletions lib/checkexceptionsafety.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -296,24 +296,22 @@ void CheckExceptionSafety::nothrowThrows()
if (!function)
continue;

// check noexcept and noexcept(true) functions
if (function->isNoExcept()) {
const Token *throws = functionThrows(function);
if (throws)
noexceptThrowError(throws);
bool isNoExcept = false, isEntryPoint = false;
if (function->isNoExcept() || // noexcept and noexcept(true) functions
(function->isThrow() && !function->throwArg) || // throw() functions
function->isAttributeNothrow()) { // __attribute__((nothrow)) or __declspec(nothrow) functions
isNoExcept = true;
}

// check throw() functions
else if (function->isThrow() && !function->throwArg) {
const Token *throws = functionThrows(function);
if (throws)
noexceptThrowError(throws);
else if (mSettings->library.isentrypoint(function->name())) {
isEntryPoint = true;
}
if (!isNoExcept && !isEntryPoint)
continue;

// check __attribute__((nothrow)) or __declspec(nothrow) functions
else if (function->isAttributeNothrow()) {
const Token *throws = functionThrows(function);
if (throws)
if (const Token* throws = functionThrows(function)) {
if (isEntryPoint)
entryPointThrowError(throws);
else
noexceptThrowError(throws);
}
}
Expand All @@ -324,6 +322,11 @@ void CheckExceptionSafety::noexceptThrowError(const Token * const tok)
reportError(tok, Severity::error, "throwInNoexceptFunction", "Exception thrown in function declared not to throw exceptions.", CWE398, Certainty::normal);
}

void CheckExceptionSafety::entryPointThrowError(const Token * const tok)
{
reportError(tok, Severity::error, "throwInEntryPoint", "Exception thrown in function that is an entry point.", CWE398, Certainty::normal);
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@danmar danmar Oct 25, 2025

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I suggest something like:

Unhandled exception is thrown in function that is an entry point.

We only warn if it's unhandled right?

This is undefined behavior right? To throw an exception that is not catched..

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@chrchr-github chrchr-github Oct 27, 2025

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Throwing in main() results in program termination: https://en.cppreference.com/w/cpp/language/throw.html
I'll add a negative test.

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@danmar danmar Oct 27, 2025 •
edited
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ok so it's defined behavior. It's not 100% clear to me that it should have "error" severity or if "warning" / "portability" would be more proper.
If program termination is wanted this is not a bad option to achieve that. However there is a danger that some RAII classes will not be destroyed properly. And using some std::exit function or something like that could be more clear about the intent.

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@chrchr-github chrchr-github Oct 27, 2025

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It looks like the outcome is the same as for throwing from a noexcept function, so the severity should also be the same.

I suggest something like:
Unhandled exception is thrown in function that is an entry point.

Should we change the message for throwInNoexceptFunction as well?

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@danmar danmar Oct 27, 2025

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It looks like the outcome is the same as for throwing from a noexcept function, so the severity should also be the same.

I agree .. it's not 100% clear to me so well we can keep it as is.

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@danmar danmar Oct 27, 2025

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Should we change the message for throwInNoexceptFunction as well?

please feel free to do it because it's only when it's not handled it's a problem. A user might think we sloppily warn whenever exceptions are thrown.

}

//--------------------------------------------------------------------------
// void func() { functionWithExceptionSpecification(); }
//--------------------------------------------------------------------------
Expand Down Expand Up @@ -433,6 +436,7 @@ void CheckExceptionSafety::getErrorMessages(ErrorLogger *errorLogger, const Sett
c.rethrowCopyError(nullptr, "varname");
c.catchExceptionByValueError(nullptr);
c.noexceptThrowError(nullptr);
c.entryPointThrowError(nullptr);
c.unhandledExceptionSpecificationError(nullptr, nullptr, "funcname");
c.rethrowNoCurrentExceptionError(nullptr);
}
1 change: 1 addition & 0 deletions lib/checkexceptionsafety.h
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Expand Up @@ -82,6 +82,7 @@ class CPPCHECKLIB CheckExceptionSafety : public Check {
void rethrowCopyError(const Token * tok, const std::string &varname);
void catchExceptionByValueError(const Token *tok);
void noexceptThrowError(const Token * tok);
void entryPointThrowError(const Token * tok);
/** Missing exception specification */
void unhandledExceptionSpecificationError(const Token * tok1, const Token * tok2, const std::string & funcname);
/** Rethrow without currently handled exception */
Expand Down
23 changes: 20 additions & 3 deletions test/testexceptionsafety.cpp
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Expand Up @@ -57,6 +57,7 @@ class TestExceptionSafety : public TestFixture {
TEST_CASE(rethrowNoCurrentException2);
TEST_CASE(rethrowNoCurrentException3);
TEST_CASE(noFunctionCall);
TEST_CASE(entryPoint);
}

struct CheckOptions
Expand Down Expand Up @@ -404,7 +405,7 @@ class TestExceptionSafety : public TestFixture {
"{\n"
" f();\n"
"}\n", dinit(CheckOptions, $.inconclusive = true));
ASSERT_EQUALS("", errout_str());
ASSERT_EQUALS("[test.cpp:4:5]: (error) Exception thrown in function that is an entry point. [throwInEntryPoint]\n", errout_str());
}

void unhandledExceptionSpecification3() {
Expand All @@ -421,12 +422,16 @@ class TestExceptionSafety : public TestFixture {
"}\n";

check(code, dinit(CheckOptions, $.inconclusive = true));
ASSERT_EQUALS("[test.cpp:3:5] -> [test.cpp:1:6]: (style, inconclusive) Unhandled exception specification when calling function f(). [unhandledExceptionSpecification]\n"
ASSERT_EQUALS("[test.cpp:10:5]: (error) Exception thrown in function that is an entry point. [throwInEntryPoint]\n"
"[test.cpp:3:5] -> [test.cpp:1:6]: (style, inconclusive) Unhandled exception specification when calling function f(). [unhandledExceptionSpecification]\n"
"[test.cpp:6:5] -> [test.cpp:1:6]: (style, inconclusive) Unhandled exception specification when calling function f(). [unhandledExceptionSpecification]\n", errout_str());

const Settings s = settingsBuilder().library("gnu.cfg").build();
check(code, dinit(CheckOptions, $.inconclusive = true, $.s = &s));
ASSERT_EQUALS("", errout_str());
ASSERT_EQUALS("[test.cpp:3:5]: (error) Exception thrown in function that is an entry point. [throwInEntryPoint]\n"
"[test.cpp:6:5]: (error) Exception thrown in function that is an entry point. [throwInEntryPoint]\n"
"[test.cpp:10:5]: (error) Exception thrown in function that is an entry point. [throwInEntryPoint]\n",
errout_str());
}

void nothrowAttributeThrow() {
Expand Down Expand Up @@ -490,6 +495,18 @@ class TestExceptionSafety : public TestFixture {
"}\n");
ASSERT_EQUALS("", errout_str());
}

void entryPoint() {
check("void f(int i) {\n" // #14195
" if (i < 2)\n"
" throw 0;\n"
"}\n"
"int main(int argc, char* argv[]) {\n"
" f(argc);\n"
"}\n");
ASSERT_EQUALS("[test.cpp:6:5]: (error) Exception thrown in function that is an entry point. [throwInEntryPoint]\n",
errout_str());
}
};

REGISTER_TEST(TestExceptionSafety)