Weak symbols (marked with __weak) are a linker-level feature that lets library and framework authors define default function implementations that developers can override simply by providing their own function with the same name. Commonly used in embedded systems for interrupt handlers and callbacks, they allow code to compile successfully without requiring developers to implement every possible handler. Overriding is straightforward — any non-weak function with the same name takes precedence at link time. However, weak symbols are not part of the C standard, making them compiler-specific and potentially non-portable. Drawbacks include reduced toolchain error detection when expected overrides are missing.
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