Fix #11311 Do not search for null pointer in dead code

[francois-berder]

No description provided.

[francois-berder]

@chrchr-github
I fixed this typo.

Unfortunately, I could not find a way to skip tokens of the "false" branch when processing the ternary operator. I can see a function named skipTernaryOp but that does not seem to do what I want. Any suggestions how to skip tokens of a ternary operator branch safely?

[chrchr-github]

What kind of code do you have in mind?
There is no warning for e.g.

int f(const int* p) {
	if (p)
		return 0;
	return 0 ? *p : 1;
}

[pfultz2]

findTokensSkipDeadCode is the function you want to use. It should skip the ternary operator as well.

[francois-berder]

Converting this PR to draft.
I am trying to handle more scenarios such as else if branch, nested branches, etc.

[pfultz2]

There should be no need to reinvent the wheel here. findTokensSkipDeadCode should work for nested branches, else if, early returns, lambda captures, and ternary operator, and it can be easily extended to handle unevaluated functions as well.

[francois-berder]

There should be no need to reinvent the wheel here. findTokensSkipDeadCode should work for nested branches, else if, early returns, lambda captures, and ternary operator, and it can be easily extended to handle unevaluated functions as well.

You are right, using findTokensSkipDeadCode makes it much easier to fix this bug.

[francois-berder]

@pfultz2 @chrchr-github I think this PR is now again ready for review.

[danmar]

could you clarify what will tok->previous() be. if there is parenthesis like ...)tok.. or something then you want to return true?

[francois-berder]

I want to make sure that the following code does not trigger a warning.

void f(type* p) {
   x(sizeof ( (p[0])));
    if (!p)
        ;
}

I need to check whether the variable p is unevaluated so I used a similar method found in checkuninitvar.cpp (see method CheckUninitVar::checkExpr).

[pfultz2]

This should be checked in findTokensSkipDeadCodeImpl function.

[francois-berder]

@danmar @pfultz2 I updated my PR to move this in findTokensSkipDeadAndUnevaluatedCode function because I was not very happy with the way I detected unevaluated pointers.

[francois-berder]

@danmar @pfultz2 @chrchr-github ping