Ada/SPARK, Swift, Go and C# are alternatives worth evaluating, but none is a universal replacement for Rust. The right choice depends on the protections the language enforces by default, the runtime and hardware you must support, the assurance requirements, and how the code will interact with existing C or C++.
What counts as a memory-safe alternative?
“Memory safe” is not a single all-or-nothing property. A language can prevent many memory errors in ordinary code while still allowing escape hatches, unsafe libraries or foreign-function interfaces (FFIs) to bypass those protections. OpenSSF describes this as a continuum: assess the defaults and the boundaries around them, rather than treating a language label as a guarantee about an entire program. OpenSSF’s Memory Safety Continuum also recommends considering dependencies and how teams review and manage those boundaries.
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For systems work, memory safety is only one part of the decision. You also need to establish whether the language and its runtime fit the target, timing and allocation constraints, how it integrates with existing code, and whether the available tools and team experience meet the project’s needs.
How the main alternatives compare
| Language or approach | What the cited guidance establishes | What to evaluate for your system |
|---|---|---|
| Ada / SPARK | NIST identifies SPARK as suitable for high-integrity applications and describes Ada as supporting embedded, real-time and systems programming. | Check the assurance or certification regime, required language subset, compiler and library availability, and team skills. These general descriptions do not establish that a particular Ada program or toolchain meets your project’s requirements. |
| Swift | Swift’s language guide documents protections against uninitialized use, access after deallocation, out-of-bounds array access and conflicting access. It also explains that exclusive access is stricter than memory safety: some nonexclusive access is accepted when the compiler can prove it safe. | Verify support for your specific targets, runtime and allocation constraints, systems interfaces, and the treatment of unsafe code and FFI boundaries. The cited documentation does not establish suitability for a particular deployment target. |
| Go | OpenSSF names Go as memory-safe by default and notes ecosystem practices such as race detection and vulnerability tooling. | Determine whether its runtime and allocation model fit the target and timing requirements. The cited guidance does not establish that Go suits a particular bare-metal or hard real-time system. |
| C# | OpenSSF names C# as memory-safe by default. | Assess the runtime and deployment model, target availability and interoperability for the specific system. |
| Rust as a baseline | NIST describes Rust’s ownership model as providing compile-time memory and thread safety without requiring a garbage collector. OpenSSF notes that unsafe blocks and FFI remain boundaries to review. | Compare the team’s Rust experience, integration costs and unsafe-code review needs with the alternatives. Rust’s safe subset is not a claim that every Rust program is automatically safe. |
Sources: NIST’s Safer Languages guidance (updated May 1, 2026); The Swift Programming Language: Memory Safety (documentation identifies Swift 6.4); and OpenSSF’s Memory Safety Continuum.
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Which option fits which kind of project?
Consider Ada/SPARK for high-integrity or embedded work
Ada/SPARK is a credible candidate when high-integrity requirements are central, and Ada is explicitly associated with embedded, real-time and systems programming in NIST’s guidance. Treat that as a reason to investigate it, not as proof that a particular implementation satisfies a certification or safety case. Confirm the exact language subset, toolchain, libraries and assurance evidence your project needs.
Consider Swift when its platform and interfaces fit
Swift has documented language-level protections for initialization, object lifetime, collection bounds and access conflicts. Those properties can be useful, but the language guarantees alone do not determine whether Swift fits a particular systems target. Validate target support and runtime characteristics for the actual deployment, and identify every unsafe or foreign interface that crosses the language’s protections.
Consider Go or C# when their runtime model is acceptable
OpenSSF identifies both Go and C# as memory-safe by default. That makes them candidates where their runtime and deployment models fit—not automatic choices for low-level, bare-metal or tightly timed work. Decide against the concrete target, resource budget and interface requirements; the cited guidance does not provide a project-specific fit assessment.
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Keep Rust in the comparison when low-level control matters
Microsoft’s systems-programming case for Rust emphasizes low-level control and predictable performance alongside compile-time protections in safe Rust. It also identifies unsafe code and C++ interoperability as adoption concerns. Those points make Rust a useful baseline, not a reason to assume it is best for every project. Microsoft’s explanation dates from July 22, 2019, so it should be read as that article’s argument rather than as a current, comparative benchmark.
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How to choose without overstating the guarantees
Before selecting a language, answer these project-specific questions:
- What is protected by default? Identify which memory errors ordinary code prevents and where unsafe features or libraries can bypass that behavior.
- What does the target allow? Check operating system, hardware, runtime, allocation and timing constraints against the actual deployment environment.
- What assurance evidence is required? For high-integrity work, determine the applicable process and toolchain requirements rather than inferring compliance from a language name.
- How will it meet existing code? Map C/C++ interfaces, dependencies and FFI boundaries, and decide how they will be isolated and reviewed.
- Can the team sustain it? Account for libraries, debugging and security tooling, compiler support, skills and long-term maintenance.
There is no supported universal ranking of these languages across those dimensions. The best candidate is the one whose protections and operational model match the project’s requirements, with its escape hatches and integration risks made explicit.
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Do you need to rewrite existing C or C++?
No. NSA and CISA state that adopting memory-safe languages does not require completely rewriting existing code and describe using interoperability to integrate them with existing codebases. OpenSSF likewise recommends practical, incremental improvements: use memory-safe-by-default languages for new software where feasible, add memory-safe abstractions around legacy code, and consider targeted rewrites of especially vulnerable components rather than mass rewriting.
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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11- Use a memory-safe-by-default language for suitable new components. Decide where it can be introduced without violating target or integration constraints.
- Prioritize risky existing components. Focus attention on high-use or especially vulnerable areas rather than assuming every line needs replacement.
- Define and review boundaries. Track unsafe code, FFI and dependencies, and include them in code review and security tooling plans.
- Integrate incrementally. Preserve necessary interfaces and validate behavior as components are added or replaced.
These approaches are described in the NSA and CISA announcement of their June 24, 2025 guidance and OpenSSF’s Memory Safety Continuum. Incremental adoption reduces the need for a wholesale rewrite; it does not make legacy code, dependencies or language-boundary code safe automatically.
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Why memory safety matters—and what one statistic does not show
In a July 22, 2019 post, Microsoft’s Security Response Center said that roughly 70% of the security issues to which it assigned a CVE were memory-safety issues. That figure applies to MSRC’s stated scope and publication at that time; it is not a current industry-wide rate. It illustrates why memory safety can be an important design concern, but it does not by itself identify the right language for a particular system. MSRC’s post discusses Rust in the context of its safe subset and low-level systems programming.
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