Why Do I Get 'Undefined Reference to' Errors When Linking a Static C Library with C Code?

Handling "Undefined Reference to" Errors When Linking Static C Library with C Code

When attempting to link a static C library with C code, it's common to encounter "undefined reference to" errors. These errors arise even after adjusting the order of object files and linking flags. However, this issue is exclusive to C linking, as other C programs using the same library do not experience these errors.

The Root Cause: Name Mangling

The key distinction between C and C compilation is name mangling. C programmers can freely use function names as declared, while C mangles the names of functions, classes, and templates to prevent naming conflicts when compiling multiple source files.

When linking a static C library with C code, the linker expects the mangled symbol names as references. However, the C library provides unmangled symbols, leading to the "undefined reference to" errors.

The Solution: Suppressing Name Mangling

To resolve these errors, the extern "C" block can be used to suppress C name mangling for a specific scope, enclosing the function declarations that interact with the C library. By doing so, the linker will recognize the unmangled references and successfully link the library.

Another effective approach is to wrap the function declarations in a header file with preprocessor directives that conditionally compile based on whether the compilation is C or C . This approach ensures that the correct function names are used depending on the compilation context.

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