[Wenzel]

Fixes #123

Summary

add_architecture_hint, repro and solution passed the caller's char * straight to CStr::from_ptr. A NULL pointer (e.g. Python None) is UB and segfaults Simics. Since ? only covers the UTF-8 check, which runs after the read, it doesn't catch this.

 add_architecture_hint / repro / solution
-  unsafe { CStr::from_ptr(ptr) }.to_str()?
+  unsafe { c_str_arg(ptr, "name") }?   // util: ensure!(!ptr.is_null()) then from_ptr

A NULL now returns an error like any other invalid argument. The generated ffi(expect) wrapper then reports it as Failed to execute FFI method solution: message must not be NULL. Non-NUL-terminated or dangling pointers can't be detected from Rust, so that stays the caller's contract. c_str_arg is an unsafe fn with a # Safety section.

Evidence

New test tests/null_string_args_latest.rs loads tsffs and calls tsffs.iface.fuzz.solution(1, None).

• Before: Segmentation fault (SIGSEGV) in main thread ("simics") from libc at test.py line 5. Test FAILED.
• After: Simics aborts with the must not be NULL panic message. Test ok. cargo clippy --all-targets is clean.

Merge Danger

Door: two-way

Blast Radius: small

Only NULL inputs behave differently. They used to crash Simics with a segfault; now they abort through the existing interface-error panic path with a clear message.

[Copilot]

Warning

Copilot couldn't run its full agentic review because it didn't start before the timeout. Make sure your repository has a runner available, or add a copilot-code-review.yml file specifying one with the runs-on attribute. See the docs for more details.

Copilot review overview

2 open issues

• If to_str() fails due to invalid UTF-8, the resulting error won’t include which argument was… · New
• The <'a> -> &'a str return type is easy to misuse because 'a is unconstrained (it’s not tied to… · New

What changed in this PR

Prevents UB/segfaults when Simics interface methods receive NULL string pointers by rejecting NULL before calling CStr::from_ptr, and adds a regression test for the reported crash.

Changes:

• Added util::c_str_arg helper to reject NULL and convert C string args safely (w.r.t. NULL).
• Updated interface methods (add_architecture_hint, repro, solution) to use c_str_arg instead of CStr::from_ptr directly.
• Added regression test ensuring None/NULL string args fail with a clear error rather than segfaulting.

File	Description
tests/​null_string_args_latest.rs	Adds regression coverage for NULL string interface argument handling.
src/​util/​mod.rs	Introduces c_str_arg helper to reject NULL prior to C string conversion.
src/​interfaces/​fuzz.rs	Switches string pointer handling in repro/solution to the new helper.
src/​interfaces/​config.rs	Switches add_architecture_hint to the new helper.

_{Review effort: Lite}