CODEWITHSUNDEEP
c++cppcheck
Ricky Goloski
Ricky Goloski

Reputation: 53

How do you perform cppcheck cross-translation unit (CTU) static analysis?

Cppcheck documentation seems to imply analysis can be done across multiple translation units as evidenced by the --max-ctu-depths flag. This clearly isn't working on this toy example here:

main.cpp:

int foo();
int main (void)
{
    return 3 / foo();
}

foo.cpp:

int foo(void)
{
    return 0;
}

Even with --enable=all and --inconclusive set, this problem does not appear in the report. It seems like cppcheck might not be designed to do cross-file analysis, but the max-ctu-depths flag begs to differ. Am I missing something here? Any help is appreciated!

Upvotes: 3

Views: 1396

Answers (2)

Daniel Marjamäki
Daniel Marjamäki

Reputation: 3037

I am a cppcheck developer.

The whole program analysis in Cppcheck is quite limited. We have some such analysis but it is not very "deep" nor sophisticated. It only currently tracks values that you pass into functions.

Some example test cases (feel free to copy/paste these code examples into different files): https://github.com/danmar/cppcheck/blob/main/test/testbufferoverrun.cpp#L4272 https://github.com/danmar/cppcheck/blob/main/test/testbufferoverrun.cpp#L4383 https://github.com/danmar/cppcheck/blob/main/test/testbufferoverrun.cpp#L4394 https://github.com/danmar/cppcheck/blob/main/test/testnullpointer.cpp#L3281 https://github.com/danmar/cppcheck/blob/main/test/testuninitvar.cpp#L4723

.. and then there is the whole unused functions checker.

If you are using threads then you will have to use --cppcheck-build-dir to make CTU possible.

Upvotes: 5

dfrib
dfrib

Reputation: 73186

Based on the docs and the source code (as well as the associated header) of the CTU checker, it does not contain a cross-translation unit divide by zero check.

One of the few entry points to the CTU class (and checker) is CTU::getUnsafeUsage, which is described (in-code) as follows:

std::list<CTU::FileInfo::UnsafeUsage> CTU::getUnsafeUsage(...) {
  std::list<CTU::FileInfo::UnsafeUsage> unsafeUsage;

  // Parse all functions in TU
  const SymbolDatabase *const symbolDatabase = tokenizer->getSymbolDatabase();

  for (const Scope &scope : symbolDatabase->scopeList) {
    // ...

    // "Unsafe" functions unconditionally reads data before it is written..
    for (int argnr = 0; argnr < function->argCount(); ++argnr) {
      // ...
    }
  }

  return unsafeUsage;
}

with emphasis on ""Unsafe" functions unconditionally reads data before it is written..".

There is no single mention on divide by zero analysis in the context of the CTU checker.

It seems like cppcheck might not be designed to do cross-file analysis

Based on the brevity of the public API of the CTU class, it does seem cppchecks cross-file analysis is indeed currently somewhat limited.

Upvotes: 2

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