Why does C++ inline function has call instructions?

Question

I read that with inline functions where ever the function call is made we replace the function call with the body of the function definition.

According to the above explanation there should not be any function call when inline is user.

If that is the case Why do I see three call instructions in the assembly code ?

#include <iostream> inline int add(int x, int y) { return x+ y; } int main() { add(8,9); add(20,10); add(100,233); } meow@vikkyhacks ~/Arena/c/temp $ g++ -c a.cpp meow@vikkyhacks ~/Arena/c/temp $ objdump -M intel -d a.o 0000000000000000 <main>: 0: 55 push rbp 1: 48 89 e5 mov rbp,rsp 4: be 09 00 00 00 mov esi,0x9 9: bf 08 00 00 00 mov edi,0x8 e: e8 00 00 00 00 call 13 <main+0x13> 13: be 0a 00 00 00 mov esi,0xa 18: bf 14 00 00 00 mov edi,0x14 1d: e8 00 00 00 00 call 22 <main+0x22> 22: be e9 00 00 00 mov esi,0xe9 27: bf 64 00 00 00 mov edi,0x64 2c: e8 00 00 00 00 call 31 <main+0x31> 31: b8 00 00 00 00 mov eax,0x0 36: 5d pop rbp 37: c3 ret

NOTE

Complete dump of the object file is here

inline is just a suggestion. It's not a requirement. If you want to force it to inline, see: stackoverflow.com/questions/8381293/… — Mysticial
– Mysticial, Commented Jun 11, 2014 at 18:44
@Mysticial this isn't jumping to a function or anywhere useful, however. It jumps to the next line. — John Dvorak
– John Dvorak, Commented Jun 11, 2014 at 18:46
@Mysticial That can explain those useless argument moves, but where has the addition gone? Also, how did GCC produce this? — John Dvorak
– John Dvorak, Commented Jun 11, 2014 at 18:48
@JanDvorak lol, dead code. I guess GCC still does some things even without optimizations. — Mysticial
– Mysticial, Commented Jun 11, 2014 at 18:49

fjardon · Accepted Answer · 2014-06-11 18:57:27Z

6

You did not optimize so the calls are not inlined
You produced an object file (not a .exe) so the calls are not resolved. What you see is a dummy call whose address will be filled by the linker
If you compile a full executable you will see the correct addresses for the jumps

See page 28 of: http://www.cs.princeton.edu/courses/archive/spr04/cos217/lectures/Assembler.pdf