Inconsistent assertWithSideEffect

[Nikita Leontiev]

cppcheck 2.20.0 generates assertWithSideEffect for the following code:
flag.h

class Flag
{
private:
    long m_flag;
public:
    Flag() : m_flag(1) {}
    bool is_set();
};

flag.cpp

#include <windows.h>
#include "flag.h"

bool Flag::is_set()
{
    return InterlockedCompareExchange(&m_flag, 0, 0)?true:false;
}

main.cpp

#include <assert.h>
#include "flag.h"

int main()
{
    assert(Flag().is_set());
}

test\main.cpp:6:16: warning: Assert statement calls a function which may have desired side effects: 'is_set'. [assertWithSideEffect]
 assert(Flag().is_set());
               ^

Moving code to a single source:

#include <assert.h>
#include <windows.h>

class Flag
{
private:
    long m_flag;
public:
    Flag() : m_flag(1) {}
    bool is_set()
    {
        return InterlockedCompareExchange(&m_flag, 0, 0)?true:false;
    }
};

int main()
{
    assert(Flag().is_set());
}

assertWithSideEffect is not generated.

[CHR]

Thanks for reporting, ticket is here: https://trac.cppcheck.net/ticket/14796