Invalid variable-length array

Overview

Use this check to detect negative array bounds. Variable-length arrays with a negative length have undefined behavior, and may cause stack corruption. Available in Xcode 9 and later.

Negative variable-length array bounds in C

In the following code, the call to the invalid_index_returning_function function returns a negative number that results in an invalid array:

int invalid_index_returning_function() {
    return -1;
}
int idx = invalid_index_returning_function();
int array[idx]; // Error: invalid array length

Solution

Fix the issue by checking array bounds before constructing arrays.

See Also

Undefined Behavior Sanitizer

• Misaligned pointer
• Invalid Boolean value
• Out-of-bounds array access
• Invalid enumeration value
• Reaching of unreachable point
• Dynamic type violation
• Invalid float cast
• Division by zero
• Nonnull argument violation
• Nonnull return value violation
• Nonnull variable assignment violation
• Null reference creation and null pointer dereference
• Invalid object size
• Invalid shift
• Integer overflow