Maximal Min() and Max()

Recent changes to the min() and max() macros in the Linux kernel have led to significant increases in compilation time, raising concerns among developers. The kernel, which heavily utilizes the C preprocessor, faced issues when the complexity of these macros grew due to attempts to enhance type safety and flexibility. The original min() and max() macros, which were simple comparisons, evolved into more complex forms that could handle various types but resulted in excessive code expansion during compilation. A specific line of code in the kernel was identified as particularly problematic, expanding to an enormous 47MB of preprocessor output due to nested calls and multiple evaluations.

In response to the compilation delays, developers discussed potential solutions, with some suggesting a reversion to simpler macros. Linus Torvalds expressed discomfort with the complexity of the current macros and proposed introducing new, simpler macros for constant expressions, which would not perform type checking but would be more efficient. These new macros were implemented to alleviate some of the compilation time issues, although they do not completely resolve the underlying problems associated with the existing min() and max() macros. The situation highlights the challenges of using the C preprocessor extensively and the need for careful consideration of macro complexity in kernel development. Further adjustments to the macros are anticipated as developers continue to address the compilation efficiency concerns.