Between C and Rust
The systems programming world has largely settled into two camps: C/C++ developers who prioritize control and compatibility, and Rust developers who accept borrow checker overhead for guaranteed memory safety. Zig occupies a different position — it offers meaningful safety improvements over C while maintaining the simplicity and transparency that C programmers value.
For security practitioners evaluating Zig for infrastructure, embedded systems, or performance-critical components, the question is not whether Zig is "safe enough" in abstract terms. The question is whether Zig's safety features are sufficient for your specific threat model.
Zig's Safety Features
Compile-Time Safety
Zig's compiler performs several checks that catch bugs before runtime:
Type system enforcement. Zig's type system is stricter than C's. Implicit type conversions that are common in C (and are a source of bugs) are errors in Zig. Integer overflow behavior is defined: in safe modes, overflow is a detectable error; in optimized builds, it becomes undefined behavior (like C) unless you use wrapping or saturating arithmetic explicitly.
Comptime execution. Zig's compile-time code execution (comptime) evaluates expressions during compilation. This eliminates certain categories of runtime errors by resolving values at build time. It also enables type-safe generic programming without the template complexity of C++.
No hidden control flow. Zig does not have exceptions, operator overloading, or hidden function calls. The code you read is the code that executes. This transparency makes security auditing significantly easier than in C++ where constructors, destructors, and operator overloads can hide complex behavior.
Runtime Safety
Zig provides optional runtime safety checks that are enabled in debug and safe builds:
Bounds checking. Array and slice access is bounds-checked in safe modes. Out-of-bounds access produces a runtime error instead of undefined behavior. This catches buffer overflows — the most common memory safety vulnerability class.
Null pointer checking. Zig's optional types make null handling explicit. Accessing an optional value without checking for null is a compile-time error. Pointer types are non-nullable by default; nullable pointers are explicitly typed as ?*T.
Use-after-free detection. In debug builds, Zig's allocator can detect some use-after-free patterns. The general-purpose allocator fills freed memory with specific patterns and checks for writes to freed memory.
Integer overflow detection. In safe builds, integer operations that overflow produce a runtime error rather than silently wrapping. This catches a category of bugs that has led to numerous CVEs in C code.
What Zig Does NOT Guarantee
No borrow checker. Zig does not track ownership or lifetimes at compile time. You can create dangling pointers, use-after-free bugs, and data races — the compiler will not stop you. These categories of bugs must be caught through testing, fuzzing, or runtime checks rather than compile-time analysis.
Safety checks are optional. The ReleaseFast build mode disables runtime safety checks for maximum performance. If your production binary is built with ReleaseFast, you lose bounds checking, overflow detection, and other safety features. This is a deliberate trade-off — Zig assumes you test thoroughly in safe modes and ship optimized builds.
Manual memory management. Zig uses explicit allocators rather than garbage collection. Memory leaks, double frees, and use-after-free are all possible. Zig's allocator interface makes memory management more structured than C's raw malloc/free, but the responsibility remains with the programmer.
C interop risks. Zig has first-class C interoperability. When you call C code from Zig, all of C's safety issues apply. The boundary between Zig and C code needs particular security attention.
Security Comparison Matrix
When comparing safety features relevant to common vulnerability classes:
Buffer overflows: Zig catches these with bounds checking in safe builds. Rust prevents them at compile time. C has no protection.
Use-after-free: Zig has limited runtime detection in debug builds. Rust prevents these at compile time through the borrow checker. C has no protection.
Null pointer dereference: Zig prevents these at compile time through optional types. Rust prevents them through its Option type. C has no protection.
Data races: Zig has no compile-time protection. Rust prevents most data races through ownership rules. C has no protection.
Integer overflow: Zig detects these at runtime in safe builds. Rust panics on overflow in debug and wraps in release. C has undefined behavior for signed overflow.
Practical Security Implications
When Zig's Safety Is Sufficient
Zig's safety features are likely sufficient for:
- Performance-critical components where the safety overhead of Rust's borrow checker significantly impacts development velocity, and the code is well-tested
- C replacement projects where even partial safety improvements over C represent meaningful risk reduction
- Embedded systems where Zig's lack of hidden allocations and transparent compilation model are advantageous
- Build tools and compilers where the Zig compiler itself (and tools like Bun, which is written in Zig) demonstrate that complex software can be built safely in Zig
When Zig's Safety May Not Be Enough
Consider Rust or other memory-safe languages for:
- Network-facing parsers that process untrusted input, where buffer overflows and use-after-free are primary threat vectors
- Cryptographic implementations where memory safety bugs can leak key material
- Privilege boundaries where exploitation of memory corruption leads directly to privilege escalation
- Multi-threaded concurrent code where data race prevention is critical
Supply Chain Considerations
Zig's package manager and build system introduce supply chain dependencies:
Zig packages are fetched from URLs (often Git repositories) and verified by hash. The build.zig.zon file records dependencies and their expected hashes. This model is similar to Go modules — URL-based with hash verification.
C library dependencies. Zig projects frequently use C libraries through Zig's C interop. These dependencies carry C's full vulnerability profile and need separate tracking and monitoring.
Build reproducibility. Zig aims for reproducible builds, which is a supply chain security advantage. Identical source code should produce identical binaries, making it possible to verify that build artifacts match source code.
How Safeguard.sh Helps
Zig projects that integrate C libraries inherit C's vulnerability landscape. Safeguard tracks both Zig package dependencies and C library dependencies, providing unified vulnerability monitoring across the language boundary. When a CVE is published against a C library your Zig project links, Safeguard identifies the exposure and alerts your team. For organizations evaluating Zig for security-critical components, Safeguard provides the supply chain visibility needed to manage the risks that Zig's safety features do not address.