Front-ends and modes in symtab2gb

[martin-cs]

I don't yet have a reproducer for this issue but it seems that there is a design / architectural problem.

1. symtab2gb only loads the json_symtab language:
   

   cbmc/src/symtab2gb/symtab2gb_parse_options.cpp

   Line 115 in 665abf7

   register_language(new_json_symtab_language);

2. It calls linking. The error reporting of linking calls from_type which uses the mode of the symbol:
   linkingt::copy_symbols
linkingt::duplicate_non_type_symbol
linkingt::duplicate_code_symbol
linkingt::detailed_conflict_report
linkingt::detailed_conflict_report_rec
linkingt::type_to_string_verbose
from_type

3. At the moment having the mode as anything other than "json_symtab" will result in an invariant failure.

So, potential work-arounds or solutions:

• Set the mode of all inputs using this interface to "json_symtab" ( paging @danielsn for the connection to RFC: Language mode for Rust  #6219 ).
• Add the C language interface to symtab2gb and set the mode to ID_C (as it is at the moment).
• Create modes for the various languages using this front-end and load all of them.

( See also #6219 (comment) )

[chrisr-diffblue]

While its not the biggest problem in the world, it does seem that adding more 'language modes' to json_symtab_language makes it an increasing maintenance burden over time (e.g. harder to add sensible invariants, easier for language specific implementation details to leak into dark corners of code, etc). I think I prefer the proposals in #6219 personally (see comments I'm about to add there...)

[martin-cs]

#6233 works around this issue by supporting mode ID_C . To be resolved properly as part of #6219 .