How do I turn off a static code analysis warning on a line by line warning in CDT (C code)?

Question

We have a project using CDT in Eclipse. It's an old project that we just imported into Eclipse, and I want to ensure we start using static code analysis to find any weirdnesses.

The thing is, there are a bunch of lines that trigger warnings that we want to just ignore, with the main ones being fallthroughs within switch statements.

I know how to do this for lint, but what about for CDT? Is there a single-line comment that I can put right above the line?

Example: ("No break at the end of case")

  case enChA:  
    nChannel++;
    // I want to ignore this fallthrough       
  case enChB:      
    nChannel++;
    // And this one...
  case enChC:
    nChannel++;
    // And this one...
  case enChD:
    nChannel++;
    // do some more stuff...
    break;

Answer 1

You should try

//no break

before the next case.

Answer 2

These settings are located under Window -> Preferences -> C/C++ -> Code Analysis. You can customize the settings. For example if you pick No break at the end of case, you can define the comment that suppresses the warning. By default it's "no break". So coincidentally copy/pasting the warning message into the comment worked in your case:

As you can see the text doesn't have to be an exact match and it doesn't seem to be case sensitive either.

Referring to your follow-up question about unused variables: When you customize Unused variable in file scope you can define variable names that should be ignored:

There are two cryptic predefined exceptions "@(#)" and "$Id". Unfortunately I couldn't find any official documentation so I went looking into the source. It looks like the checker simply tests if a variable name contains() any of the specified exceptions. If it does, the warning is suppressed.

Outside of Eclipse CDT, there's the popular void-casting trick. If the compiler warns about an unused variable, cast it to void. This operation has no effect, so it's safe, but from the perspective of the compiler that variable is now used. I usually wrap it in a macro to make abundantly clear what I'm doing, e.g.

#define UNUSED(var) (void)(var)

void foobar()
{
    int b;     // not used. 
    UNUSED(b); // now it's used
}

Answer 3

Solved it.

I just added the text from the warning that I wanted to ignore to immediately above where the break would be.

Like this:

      case enChC:
        ++nChannel;
        //No break at the end of case
      case enChD:
        ++nChannel;

Answer 4

As is has been said, in this specific case, it can be solved adding the comment:

//no break

or:

//no break at the end of case

What really matters is the (no break).

But also, it is required that you don't have more comments between the end of this case and the next one or it won't work. For example the next case will still result in a warning:

case enChC:
    ++nChannel;
    //No break
    //This second case decrease the value
  case enChD:
    ++nChannel;

Answer 5

UPDATE 2021

• Version: 2021-03 (4.19.0)
• Build id: 20210312-0638

Assuming you have this switched on

window -> Preferences -> (Your code example) C/C++ -> Code Analysis -> No break at end of case

If you go to Customize Selected..., you will get "Comment text to suppress the problem [...]" which declares which data stream will actually only change the effect but still won't fix the problem.

The relevant line is in the file org.eclipse.cdt and looks like this :

org.eclipse.cdt.codan.internal.checkers.CaseBreakProblem.params={launchModes=>{RUN_ON_FULL_BUILD=>true,RUN_ON_INC_BUILD=>true,RUN_ON_FILE_OPEN=>false,RUN_ON_FILE_SAVE=>false,RUN_AS_YOU_TYPE=>true,RUN_ON_DEMAND=>true},suppression_comment=>"@suppress(\"No break at end of case\")",no_break_comment=>"no break",last_case_param=>false,empty_case_param=>false,enable_fallthrough_quickfix_param=>false}

• Having this like in my example will work with the code below.

• Note that the content of the comment does not matter, but it must contain an identical fragment corresponding to the settings contained in the Eclipse itself

• Additionally, it is important to put the comment after the } character, unless it is a single argument case

• Eclipse will still report the problem and this cannot be avoided in any way by having the bug report enabled in the settings, but it will no longer underline every line in the case

        switch(next) {
            case 0: {
                if(true) {
                    //Do stuff...
                } else {
                    break;
                }
                next = 1;
            }
            // ThiS Is The Line that CAUSE N"no break////////"  
            case 1: {
                if(true) {
                    //Do stuff...
                } else {
                    break;
                }
                next = 2;
            }
            case 2: {
                if(true) {
                    //Wont do stuff...
                    //It will break here
                    break;
                } else {
                    next = 3;
                }
            }
  

I present a photo that shows the effect in the eclipse itself.

Answer 6

I have encountered this question,and I just want to eliminate them. I tried to add /* no break */,you should make sure it is added before the next "case". This is the question I have encountered

This is the solution I use：