Precompiled Headers in C/C++ Projects

2023/07/17

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Precompiled headers can greatly improve compile time in C/C++ projects. While C++ modules have emerged as an alternative, precompiled headers still remain relevant for several reasons. This article focuses on Clang precompiled headers (PCH) and provides an example to illustrate their usage.

To generate a precompiled header, Clang parses a header file and performs semantic analysis. The resulting precompiled header is saved as a serialized AST file. When compiling a source file, the precompiled header can be included as a prefix header using the -include-pch flag.

To avoid redefinition errors, header files should have a header guard or use #pragma once. Clang also supports the use of -include to probe for and use a precompiled header if present.

Overall, precompiled headers are a valuable tool for optimizing compile time in C/C++ projects. Developers can leverage them to speed up their builds and improve productivity.