--min_array_alignment=opt

Where:

Use of this option is not recommended, unless required in certain specialized cases. For example, porting code to systems that have different data alignment requirements. Use of this option can result in increased code size at the higher opt values, and reduced performance at the lower opt values. If you only want to affect the alignment of specific arrays (rather than all arrays), use the __align keyword instead.

If you do not use this option, arrays are unaligned (byte aligned).

Compiling the following code with --min_array_alignment=8 gives the alignment described in the comments:

char arr_c1[1];      // alignment == 8
char c1;             // alignment == 1