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V568. It is suspicious that the argument of sizeof() operator is the expression.
The analyzer detected a potential error: a suspicious expression serves as an argument of the sizeof() operator.
Suspicious expressions can be arranged in two groups:
1. An expression attempts to change some variable.
The sizeof() operator calculates the expression's type and returns the size of this type. But the expression itself is not calculated. Here is a sample of suspicious code:
int A;
...
size_t size = sizeof(A++);This code does not increment the 'A' variable. If you need to increment 'A', you'd better rewrite the code in the following way:
size_t size = sizeof(A);
A++;2. Operations of addition, multiplication and the like are used in the expression.
Complex expressions signal errors. These errors are usually related to misprints. For example:
SendDlgItemMessage(
hwndDlg, RULE_INPUT_1 + i, WM_GETTEXT,
sizeof(buff - 1), (LPARAM) input_buff);The programmer wrote "sizeof(buff - 1)" instead of "sizeof(buff) - 1". This is the correct code:
SendDlgItemMessage(
hwndDlg, RULE_INPUT_1 + i, WM_GETTEXT,
sizeof(buff) - 1, (LPARAM) input_buff);Here is another sample of a misprint in program text:
memset(tcmpt->stepsizes, 0,
sizeof(tcmpt->numstepsizes * sizeof(uint_fast16_t)));The correct code:
memset(tcmpt->stepsizes, 0,
tcmpt->numstepsizes * sizeof(uint_fast16_t));3. The argument of the sizeof() operator is a pointer to a class. In most cases this shows that the programmer forgot to dereference the pointer.
Example:
class MyClass
{
public:
int a, b, c;
size_t getSize() const
{
return sizeof(this);
}
};The getSize() method returns the size of the pointer, not of the object. Here is a correct variant:
size_t getSize() const
{
return sizeof(*this);
}This diagnostic is classified as:
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You can look at examples of errors detected by the V568 diagnostic. |
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