Question

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How does a compiled C++ class look like?

Hi all,

 bash$cat struct.c
struct test
{
int i;
float f;
};

bash$gcc -c struct.c

The object file struct.o is of elf format. I am trying to understand what does this object file contain. The source code is just a definition of a struct. There is nothing executable here so there should be nothing in text, and there is no data really either.
So where does the definition of struct go really?

I tried using;

readelf -a struct.o
objdump -s struct.o

but don’t quite understand this.

Thanks,

Jagrati

Answer 1

So where does the definition of struct
go really?

Struct definition usually goes to /dev/null. C does not have any introspection features, so struct definition is not needed at run time. During compilation, calls to struct fields are converted to numeric offsets, eg. x->f would be compiled to equivalent of *((void*)x + sizeof(int)). That’s why you need to include headers every time you use struct.