主要有以下几个步骤：
- 预处理, g++ 参数为 -E
- 编译, g++ 参数为 -S
- 汇编, g++ 参数为 -c, 只激活预处理，编译和汇编
- 链接
基本的编译系统如下图所示：
预处理 （Pre-preocessor）
以一个”hello.cc”为例，文件大小为1kb.它的c++代码如下：
#include <iostream>
using namespace std;
int main(){
cout<<"Hello World"<<endl;
} 进过编译指令’gcc -E hello.cc’,输出的”hello.i”文件的大小为411kb,经过查看 ，主要是 using namespace这一句占用了基本上大部分的文件大小。其主要不同是将原来在不同文件中定义的代码 直接写进了输出的”hello.i”中。
编译 (Compile)
编译的主要作用是将预处理后的代码变成汇编语言。以上段所生成的”.i”为例，编译的gcc命令为’g++ -S hello.i’。 本例中生成的汇编语言代码如下：
.file "hello_post_prep.cc"
.lcomm __ZStL8__ioinit,1,1
.def ___main; .scl 2; .type 32; .endef
.section .rdata,"dr"
LC0:
.ascii "Hello World\0"
.text
.globl _main
.def _main; .scl 2; .type 32; .endef
_main:
LFB952:
.cfi_startproc
leal 4(%esp), %ecx
.cfi_def_cfa 1, 0
andl $-16, %esp
pushl -4(%ecx)
pushl %ebp
.cfi_escape 0x10,0x5,0x2,0x75,0
movl %esp, %ebp
pushl %ecx
.cfi_escape 0xf,0x3,0x75,0x7c,0x6
subl $20, %esp
call ___main
movl $LC0, 4(%esp)
movl $__ZSt4cout, (%esp)
call __ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
movl $__ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_, (%esp)
movl %eax, %ecx
call __ZNSolsEPFRSoS_E
subl $4, %esp
movl $0, %eax
movl -4(%ebp), %ecx
.cfi_def_cfa 1, 0
leave
.cfi_restore 5
leal -4(%ecx), %esp
.cfi_def_cfa 4, 4
ret
.cfi_endproc
LFE952:
.def ___tcf_0; .scl 3; .type 32; .endef
___tcf_0:
LFB962:
.cfi_startproc
pushl %ebp
.cfi_def_cfa_offset 8
.cfi_offset 5, -8
movl %esp, %ebp
.cfi_def_cfa_register 5
subl $8, %esp
movl $__ZStL8__ioinit, %ecx
call __ZNSt8ios_base4InitD1Ev
leave
.cfi_restore 5
.cfi_def_cfa 4, 4
ret
.cfi_endproc
LFE962:
.def __Z41__static_initialization_and_destruction_0ii; .scl 3; .type 32; .endef
__Z41__static_initialization_and_destruction_0ii:
LFB961:
.cfi_startproc
pushl %ebp
.cfi_def_cfa_offset 8
.cfi_offset 5, -8
movl %esp, %ebp
.cfi_def_cfa_register 5
subl $24, %esp
cmpl $1, 8(%ebp)
jne L4
cmpl $65535, 12(%ebp)
jne L4
movl $__ZStL8__ioinit, %ecx
call __ZNSt8ios_base4InitC1Ev
movl $___tcf_0, (%esp)
call _atexit
L4:
leave
.cfi_restore 5
.cfi_def_cfa 4, 4
ret
.cfi_endproc
LFE961:
.def __GLOBAL__sub_I_main; .scl 3; .type 32; .endef
__GLOBAL__sub_I_main:
LFB963:
.cfi_startproc
pushl %ebp
.cfi_def_cfa_offset 8
.cfi_offset 5, -8
movl %esp, %ebp
.cfi_def_cfa_register 5
subl $24, %esp
movl $65535, 4(%esp)
movl $1, (%esp)
call __Z41__static_initialization_and_destruction_0ii
leave
.cfi_restore 5
.cfi_def_cfa 4, 4
ret
.cfi_endproc
LFE963:
.section .ctors,"w"
.align 4
.long __GLOBAL__sub_I_main
.ident "GCC: (GNU) 4.8.1"
.def __ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc; .scl 2; .type 32; .endef
.def __ZSt4endlIcSt11char_traitsIcEERSt13basic_ostreamIT_T0_ES6_; .scl 2; .type 32; .endef
.def __ZNSolsEPFRSoS_E; .scl 2; .type 32; .endef
.def __ZNSt8ios_base4InitD1Ev; .scl 2; .type 32; .endef
.def __ZNSt8ios_base4InitC1Ev; .scl 2; .type 32; .endef
.def _atexit; .scl 2; .type 32; .endef
