<function> cfg applying to function within a struct. v1.83

[Scott H]

Hello all,

Sorry if this has been answered somewhere already. Searches on Google and directly on the forum were both unproductive.

In our C code we have many cases of the following in our code where the int returned is a status.

typedef int (*MY_FUNCTION_TYPE) (int Argument);

typedef struct {
    MY_FUNCTION_TYPE MyFunc;
} MY_STRUCT;
...

MY_STRUCT *MyStruct;

// Assign struct pointers...

Status = MyStruct->MyFunc(Args);

In trying to make a CFG to enforce checking this status I made the following rule.

<function name="MyFunc">
    <use-retval/>
</function>  

However it only works for the first line below. Not the 2nd. Our code requires it report this error for the 2nd line.

MyFunc(Args);
MyStruct->MyFunc(Args);

I also attempted a much longer function definition with every qualified name configuration I could think of. But it gave the same results. (Forgive me, we program entierly in C, so I'm rusty with this programming syntax)

<function name="MyFunc,MyStruct->MyFunc,MY_FUNCTION_TYPE::MyFunc,MY_STRUCT::MY_FUNCTION_TYPE,MY_STRUCT::MyFunc">
    <use-retval/>
</function>  

Would anyone know how to get CppCheck to report for our case?

P.S. - Checking the CppCheck codebase I noticed that there are files for processing classes, but I didn't see one for structs. Is it possible that CppCheck does not understand our particular situation?

Thank you,
Scott

[versat]

Even without function pointers i get no warning:
struct_function.cpp:

#include <cstdio>

struct teststruct
{
    int testfunc() { printf("testfunc says hi!\n"); return 1; }
};

int main()
{
    teststruct TestStruct1;
    TestStruct1.testfunc();
}

struct_function.cfg:

<?xml version="1.0"?>
<def format="2">
  <function name="teststruct::testfunc">
    <use-retval/>
  </function>
</def>

output:

$ g++ struct_function.cpp -o struct_function

$ ./struct_function
testfunc says hi!

$ ./cppcheck --enable=all --library=struct_function.cfg --check-library --debug-warnings struct_function.cpp
Checking struct_function.cpp ...
[struct_function.cpp:5]: (debug) valueflow.cpp:3343:valueFlowFunctionReturn bailout: function return; nontrivial function body
(information) Cppcheck cannot find all the include files (use --check-config for details)

IMHO this is a false negative.
You can see that Cppcheck does not complain about a missing configuration for teststruct::testfunc which would be the case if the according function configuration is not present. So this should be the correct way to specify struct functions i guess.

[versat]

I have created ticket 8595.
Your case is a bit more complex like the one i described in the ticket. Maybe there is a bit more to fix/enhance so it works for your code too, i am not sure.

[versat]

And i nearly forgot about this ticket: https://trac.cppcheck.net/ticket/8290
I do not know if Cppcheck sees the implementation in your case and i am not sure if Cppcheck is able to track the function pointers, but if it does this could be a reason it ignores the function configuration.