# Checking Arrays

The pointer checker is not supported on macOS systems.

The C and C++ language allows you to define arrays in another module with the `extern` keyword. These arrays can be defined without specifying the dimensions.

Example: Creating an Undimensioned Array
    extern char an_undimensioned_array [];

The compiler allows more than one definition for externally defined arrays. During link time, the compiler uses the array definition with the largest bounds.

To check these arrays, the compiler defines a global symbol that marks the end of the array. However, checking undimensioned arrays can lead to a multiple defined linker error. To fix this linker error, do one of the following:

- Use only one array definition.

- Use the negative form of the [Q]check-pointers-undimensioned compiler option to disable checking arrays without bounds.

### Note

This compiler option suppresses checking in the module that declares an array without bounds. The pointer checker will still check the arrays in modules that actually define the arrays with bounds.

Parent topic: Using the Pointer Checker

## See Also

check-pointers-undimensioned, Qcheck-pointers-undimensioned compiler option