gdb: M2 Defaults
15.4.9.5 Modula-2 Defaults
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If type and range checking are set automatically by GDB, they both
default to 'on' whenever the working language changes to Modula-2. This
happens regardless of whether you or GDB selected the working language.
If you allow GDB to set the language automatically, then entering
code compiled from a file whose name ends with '.mod' sets the working
language to Modula-2. Having GDB Infer the Source Language
Automatically, for further details.