Disable mutants with annotations

This guide shows how to disable mutants using source code annotations.

There are two ways to disable/ignore a mutant using source code annotations: for single lines and for bigger blocks of code.

1. Turn Mull off for a big chunk of code:

Any mutations within the block marked by mull-off/mull-on will be ignored.

main.c

// disable all mutations from mull-off till mull-on
// mull-off
int ignore_all(int a, int b) {
    return a + b;
}
// mull-on

// disable cxx_add_to_sub from mull-off till mull-on
// mull-off: cxx_add_to_sub
int ignore_some(int a, int b, int c) {
    return a + b - c;
}
// mull-on

// disable all mutations till the end of file
// mull-off
int ignore_till_eof(int a, int b, int c) {
    return a + b - c;
}

2. Disable mutations for a single line:

main.c

int ignore_all_line(int a, int b) {
    // disable all mutations on the annotated line
    return a + b; // mull-ignore
}

int ignore_some_line(int a, int b, int c) {
    // disable cxx_add_to_sub on the annotated line
    return a + b - c; // mull-ignore: cxx_add_to_sub
}

int ignore_all_next_line(int a, int b) {
    // disable all mutations on the line following the annotation
    // mull-ignore-next
    return a + b;
}

int ignore_some_next_line(int a, int b, int c) {
    // disable cxx_add_to_sub on the line following the annotation
    // mull-ignore-next: cxx_add_to_sub
    return a + b - c;
}