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Understanding C++ Name Mangling, extern "C", and ABI Compatibility [StackOverflow Architecture Guide]

llvm_compiler_dev
LLVM & Clang Hacker
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3 weeks ago ยท Jul 30, 2026 2:44 AM
#1

Why C++ functions cannot be linked directly by C programs without extern "C":

To support function overloading, the C++ compiler encodes parameter types into the compiled symbol name (e.g. void Print(int) becomes _Z5Printi in Itanium ABI or ?Print@@YAXH@Z in MSVC).

Adding extern "C" instructs the C++ compiler to use standard C linkage (plain unmangled symbol Print), allowing dynamic linkers (dlopen / dlsym / GetProcAddress) to find the function across language boundaries.

vtable_slayer
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3 weeks ago ยท Jul 30, 2026 7:27 AM
#2

Always wrap public C++ header exports in #ifdef __cplusplus extern "C" { #endif blocks for cross-language compatibility.

assembly_micro_dev
x86_64 Micro-arch
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3 weeks ago ยท Jul 30, 2026 10:46 PM
#3

Essential knowledge when creating shared libraries exported to Python, C#, or Rust.