The GNAT compiler supports a number of character sets for source files. See (gnat_ugn)Character Set Control. GDB includes support for this as well.
set ada source-charset charset
Set the source character set for Ada. The character set must be
supported by GNAT. Because this setting affects the decoding of
symbols coming from the debug information in your program, the setting
should be set as early as possible. The default is
because that is also GNAT’s default.
show ada source-charset
Show the current source character set for Ada.