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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
Complete dump of the object file is here
799
An inline function is one for which the compiler copies the code from the function definition directly into the code of the calling function rather than creating a separate set of instructions in memory. This eliminates call-linkage overhead and can expose significant optimization opportunities.
Inline Function in C++ The main advantage of inline functions is that you can use them with C++ classes as well. When an instruction of a function call is encountered during the compilation of a program, its memory address is stored by the compiler.
Static inline functions are simple. Either a function defined with the inline function specifier is inlined at a reference, or a call is made to the actual function. The compiler can choose which to do at each reference. The compiler decides if it is profitable to inline at -xO3 and above.
Automatic function inlining and static functions At -O2 and -O3 levels of optimization, or when --autoinline is specified, the compiler can automatically inline functions if it is practical and possible to do so, even if the functions are not declared as __inline or inline .
See page 28 of: http://www.cs.princeton.edu/courses/archive/spr04/cos217/lectures/Assembler.pdf
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