The paper provides a detailed comparison between musl and glibc, two prominent C standard libraries for Linux systems, to guide users in selecting the most suitable one based on their application requirements, resource constraints, and operational priorities.

glibc, or the GNU C Library, is presented as the default and most prevalent C standard library across major Linux distributions like Ubuntu, Debian, RHEL, and Fedora. Established in 1988, it boasts decades of active maintenance, making it a mature, robust, and feature-rich library. Its widespread adoption ensures extensive compatibility with a vast ecosystem of third-party software, enterprise applications, and legacy systems, minimizing integration issues. glibc includes architecture-specific optimizations, rendering it ideal for computationally intensive tasks, I/O-heavy workloads, and large-scale systems where performance is critical. However, its comprehensive feature set results in a larger footprint, higher memory consumption, and a broader attack surface due to its extensive codebase, potentially increasing the likelihood of vulnerabilities over time, necessitating proactive security monitoring and timely patching. glibc adheres to core POSIX standards but also incorporates numerous GNU-specific extensions, which, while ensuring broad compatibility, may inadvertently encourage non-portable coding practices. It is primarily optimized for dynamic linking, with static linking being technically possible but often discouraged due to complexities with components like NSS (Name Service Switch) and the dynamic linker (ld.so).

Conversely, musl is introduced as a lightweight, modern C library designed with simplicity, speed, and static linking in mind, first released in 2011 as an alternative to glibc. Its core design philosophy prioritizes correctness and minimalism, leading to a significantly smaller binary size (core library < 1MB) and minimal memory usage. This makes musl particularly well-suited for resource-constrained environments such as ultra-compact container images (e.g., Alpine Linux base images for Docker and Kubernetes), embedded devices, and serverless functions where resource efficiency is paramount. The minimalist design of musl inherently contributes to enhanced security by reducing the code audit surface and the potential for vulnerabilities. It excels in static linking, enabling the creation of fully self-contained, portable executables without external library dependencies, which is highly beneficial for languages like Go and Rust. musl strictly adheres to POSIX standards, consciously avoiding GNU extensions, thereby promoting portability. However, this strict adherence can lead to compatibility issues with software that expects glibc's behaviors or relies on GNU extensions. Common challenges include DNS resolver quirks (e.g., issues with large responses over TCP), limited default thread stack sizes (e.g., 128KB vs. glibc's 2MB-10MB, potentially causing segmentation faults in multi-threaded applications like Python or Java), and performance bottlenecks in memory-intensive or highly parallel workloads due to its simpler internal structures, sometimes resulting in significantly slower execution. Its ecosystem and community are smaller and less mature compared to glibc, potentially requiring more manual effort for patching, building, or troubleshooting.

In summary, the choice between musl and glibc depends on specific use cases:

• glibc remains the preferred choice for general-purpose Linux operating systems, large enterprise servers, workstations, and existing infrastructure where stability, broad software compatibility, and peak performance across diverse workloads are critical. Its established ecosystem provides robust debugging and profiling tools.
• musl is a strong contender for containerized environments (especially with Alpine Linux) due to its minimal image size, faster pull times, and reduced attack surface, as well as for embedded systems where memory constraints are severe, and for applications requiring highly portable, statically linked binaries. However, users must be prepared to address potential compatibility and performance challenges, particularly in complex networking or multi-threading scenarios.

The paper concludes by emphasizing the importance of keeping the chosen C library secure and up-to-date, highlighting solutions like TuxCare's LibCare for automated critical security updates to glibc without system reboots or service interruptions, which is crucial for organizations running large glibc-based Linux servers.