Why Am I Getting Unresolved External Symbols __imp__fprintf and __imp____iob_func with SDL2?

Unresolved External Symbols: __imp__fprintf and __imp____iob_func with SDL2

In programming, encountering unresolved external symbols is a common issue that manifests as linking errors. Two specific symbols that frequently cause such errors with SDL2 are __imp__fprintf and __imp____iob_func.

The __imp__fprintf unresolved external symbol arises because fprintf, which is used for formatted printing, is located in a dynamic link library (DLL). Compilers typically link to these libraries at runtime, but sometimes the linker cannot find the appropriate DLL. This can happen when the DLL is not present in the system path or when the wrong version is linked.

The __imp____iob_func unresolved external symbol, on the other hand, is related to C's standard input/output (I/O) functions. In particular, Visual Studio 2015 introduced changes to the definition of I/O functions like stdin, stdout, and stderr. These functions are now defined using __acrt_iob_func, while in earlier versions, they were defined using __iob_func. This can cause linking errors when using libraries or code that was compiled with older versions of Visual Studio.

To resolve these unresolved external symbol errors, you can take the following steps:

• Ensure that the necessary DLLs, such as msvcrt.dll for __imp__fprintf, are present in the system path.
• Verify that you are linking to the correct version of the SDL2 libraries and DLLs.
• If __imp____iob_func is the culprit, define __iob_func yourself in your code to return an array containing {stdin,stdout,*stderr}.
• To address errors with other stdio functions, add legacy_stdio_definitions.lib to the linker options.

By following these steps, you can effectively address the unresolved external symbol errors related to __imp__fprintf and __imp____iob_func when working with SDL2 in Visual Studio 2015.

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