The GNU C Compiler (GCC) has become an unlikely foe in the fight against modern security threats. René Meusel, creator of the Botan cryptography library, warned that GCC’s aggressive optimization capabilities can undo safety precautions and expose vulnerabilities in cryptographic code.
Meusel shared his concerns at FOSDEM 2026, highlighting how the compiler’s optimization algorithms can simplify Boolean logic to the point where it becomes vulnerable to side-channel attacks. To avoid this issue, Meusel advocates for using constant-time implementations and obfuscation techniques to mask Boolean comparisons from the compiler.
However, these workarounds come with their own set of challenges, including understanding inline assembly code and managing multiple obfuscation layers. Meusel acknowledged that it’s becoming increasingly difficult for programmers to keep up with GCC’s optimizations and warned about the need for a more qualitative approach to code development.
Ultimately, security software designers must consider not only code efficiency but also other factors such as maintainability, scalability, and the tools used in their development process.
Source: https://www.theregister.com/2026/02/09/compilers_undermine_encryption