[Syphonicc]

Proposed Changes

The binary restart readers copy a user-controlled filename into a fixed char fname[100] with
strcpy, which has no bounds check. The filename comes from the config (SOLUTION_FILENAME and the
derived restart/mesh names), so a path longer than 99 characters overflows the stack buffer.

This replaces the fixed buffer and strcpy with a const char* fname = <filename>.c_str(); at each
site. The string is already in scope and is not modified between this point and the file open, so the
behaviour is identical; only the fixed-size copy is removed. All use sites (fopen, MPI_File_open,
and the error messages) are unchanged.

Sites fixed (all were char fname[100]):

• CSolver::Read_SU2_Restart_ASCII and CSolver::Read_SU2_Restart_Binary
• CBaselineSolver::Load_Restart (binary and ASCII branches)
• CBaselineSolver_FEM::Load_Restart (binary and ASCII branches)
• CPhysicalGeometry::SetBoundaries restart readers (binary and ASCII branches)

Verification

• Reproduced the overflow before the change with an AddressSanitizer build: pointing
  SOLUTION_FILENAME at a ~150-character path aborts with a stack-buffer-overflow in
  Read_SU2_Restart_Binary (the write into fname). After the change the same case runs cleanly
  under ASAN.
• axi_rans_air_nozzle_restart (reads a binary restart) reproduces the stored regression values
  exactly, confirming the readers are unaffected. The change is non-numerical, so no regression
  values change.
• No new compiler warnings.

There is one related spot left out of this PR to keep it focused: the surface-sensitivity reader in
CPhysicalGeometry uses cstr[MAX_STRING_SIZE] with strcpy/strcat (400 bytes, a different
function). Happy to address it here or in a follow-up, whichever is preferred.

Related Work

None.

PR Checklist

• I am submitting my contribution to the develop branch.
• My contribution generates no new compiler warnings (try with --warnlevel=3 when using meson).
• My contribution is commented and consistent with SU2 style (https://su2code.github.io/docs_v7/Style-Guide/).
• I used the pre-commit hook to prevent dirty commits and used pre-commit run --all to format old commits.
• I have added a test case that demonstrates my contribution, if necessary.
• I have updated appropriate documentation (Tutorials, Docs Page, config_template.cpp), if necessary.