Why is this an issue?
Empty statements, i.e. ;, are usually introduced by mistake, for example because:
- It was meant to be replaced by an actual statement, but this was forgotten.
- There was a typo which lead the semicolon to be doubled, i.e.
;;.
Noncompliant code example
void doSomething() {
; // Noncompliant - was used as a kind of TODO marker
}
#define A(x) x; // Noncompliant - macro definitions should not end with a semi-colon when they are used as functions
void fun() {
A(5); // Noncompliant - after expansion, there are 2 consecutive semi-colons
}
Compliant solution
void doSomething() {
}
#define A(x) x
void fun() {
A(5);
}
Exceptions
In the case of an empty expanded macro, the issue is not raised.
Example:
#define LOG(x)
void fun() {
LOG(X);
}
Resources
- MISRA C:2004, 14.3 - Before preprocessing, a null statement shall only occur on a line by itself; it may be followed by a comment provided that
the first character following the null statement is a white-space character.
- MISRA C++:2008, 6-2-3 - Before preprocessing, a null statement shall only occur on a line by itself; it may be followed by a comment, provided
that the first character following the null statement is a white-space character.
- CERT, MSC12-C. - Detect and remove code that has no effect or is never executed
- CERT, MSC51-J. - Do not place a semicolon immediately following an if, for, or while
condition
- CERT, EXP15-C. - Do not place a semicolon on the same line as an if, for, or while
statement
