[LLVMdev] Why are functions renamed for .cpp files with llvm-gcc?

[Owen Anderson]

On Jun 17, 2009, at 1:39 AM, Fabian Scheler wrote:

> Hi Arto,
>
>> I wonder why there is a difference in how
>> llvm-gcc compiles .c and .cpp files.
>>
>> Example:
>>
>> ---bar.cpp----
>> int bar() {
>>   return 42;
>> }
>> --------------
>>
>> $ llvm-gcc -emit-llvm -c bar.cpp
>>
>> Now running bar.o through llvm-dis gives:
>> --------------------------------
>> define i32 @_Z3barv() nounwind {
>> < clip >
>> }
>> --------------------------------
>>
>> Above, function 'bar' has been renamed to '_Z3barv'.
>>
>> If, however, 'bar.cpp' is renamed 'bar.c',
>> we get 'define i32 @bar()' as expected.
>
> The answer is: C++ name mangling


To elaborate a little bit, it's how C++ encodes namespaces, function  
overloading, etc.  It's a standard thing, and necessary for cross- 
compiler compatibility.  If you want your C++ functions to appear like  
C functions, you need to use extern "C" { }

--Owen
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