[tautschnig]

The SAT and SMT2 back ends disagreed on how to extend integer-to-pointer
and pointer-to-integer casts when the types have different widths:

• SAT: zero-extended in both directions
• SMT2: sign-extended in both directions

GCC documents that integer-to-pointer conversion extends according to
the signedness of the source integer type, and pointer-to-integer
conversion sign-extends. Neither back end matched GCC on all cases.

Fix SAT back end (bv_pointers.cpp):

• Integer to pointer: sign-extend for signed sources, zero-extend for
  unsigned sources (was: always zero-extend).
• Pointer to integer: sign-extend (was: zero-extend).

Fix SMT2 back end (smt2_conv.cpp):

• Integer to pointer: extend according to source signedness (was:
  always sign-extend).
• Pointer to integer: already correct (sign-extend), no change.

Fixes #9212

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[codecov]

Codecov Report

❌ Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 80.90%. Comparing base (266f438) to head (4e1ca5a).

Files with missing lines	Patch %	Lines
src/solvers/flattening/bv_pointers.cpp	88.88%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #9231      +/-   ##
===========================================
- Coverage    80.91%   80.90%   -0.01%     
===========================================
  Files         1718     1718              
  Lines       190266   190272       +6     
  Branches        73       73              
===========================================
- Hits        153952   153941      -11     
- Misses       36314    36331      +17     

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[kroening]

This semantics feels extremely compiler and target-specific. The C-frontend should lower the cast to the specific target semantics based on compiler and architecture setting.