CPP Interoperability & System Programming Flashcards

What is the primary purpose of extern "C" in C++?

Answer: To prevent name mangling so C code can link to C++ functions

extern "C" instructs the C++ compiler to use C linkage, preventing name mangling so the symbol can be called from C code.

Which two techniques are commonly used to prevent multiple inclusions of a header file?

Answer: Both #pragma once and #ifndef/#define/#endif

Both the portable #ifndef/#define/#endif include guard pattern and the widely-supported #pragma once compiler extension prevent double inclusion.

When calling a C library that allocates memory, how must that memory be freed in C++?

Answer: Use free()

Memory allocated by C library functions using malloc/calloc must be released with free(), not delete, to avoid undefined behavior.

What does the __cplusplus predefined macro indicate?

Answer: Whether code is compiled as C++ and which standard version is active

The __cplusplus macro is set by C++ compilers to an integer value representing the active standard, such as 201703L for C++17.

What is C++ name mangling?

Answer: The compiler encoding of a function's full signature into its binary symbol name

Name mangling encodes the full function signature (including parameter types) into the binary symbol name to support function overloading.

How should a C++ function pointer be declared to be safely passed as a callback to a C library?

Answer: As a free function or static member with extern "C" linkage

C libraries require C-linkage function pointers; a free function or static member declared with extern "C" provides the correct calling convention.