Should cppcheck flag comparing a uint32_t < 0u?

[Richard Smith]

I found the following consturct in some code that is checked with cppcheck.

uint32_t value = 0xFUL;

 <do things with value>

if (value < 0u)
{
    value = 0u;
}

The if() will never evaluate to true because its an unsigned comparison. I would have expected cppcheck to catch this but it does not seem to.

[Daniel Marjamäki]

weird! There is something about the "0u" in your code. We do warn about this code:

uint32_t value = 0xFUL;
void f() {
  if (value < 0)
  {
    value = 0u;
  }
}

[Daniel Marjamäki]

I created https://trac.cppcheck.net/ticket/8836 ... I plan to look at it in the next couple of days.

[Richard Smith]

I think something may be broken with my setup.

I compiled and installed HEAD (43b6a391d) and created the file below.

int main(void)
{
    return f();
}

uint32_t value = 0xF;

void f() {
    if (value < 0)
    {
        value = 0;
    }
}

but I don't get an error.

rsmith@gatito:/home/src/cppcheck.git/ctest$ cppcheck main.c
Checking main.c ...

[Richard Smith]

Nevermind. I figured out that I need --enable=style. The MISRA checker reports the errors as style so I assume it was on by default. But I duplicated the 'u' causing a false negative.