C 编译过程浅析

    From where i stand,

        there are two programmig languages in the world,

            which is C lang and the other.

　

编译(compile)

• 预处理(也称预编译，Preprocessing)
• 编译(Compilation)
• 汇编 (Assembly)
• 连接(Linking)

GCC参考

gcc - GNU project C and C++ compiler

If you only want some of the stages of compilation, you can use -x (or filename suffixes) to tell gcc where to start, and one of the options -c, -S, or -E to say where gcc is to stop. Note that some combinations (for example, -x cpp-output -E) instruct gcc to do nothing at all.

• -E Stop after the preprocessing stage; do not run the compiler proper.
• -S Stop after the stage of compilation proper; do not assemble.
• -c Compile or assemble the source files, but do not link.
• -o targetfile Place output in file targetfile.

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 [root@standby gcc]# date +%F_%H:%M:%S
 --29_23::
 [root@standby gcc]# pwd
 /data/gcc
 [root@standby gcc]# ll
 total
 -rw-r--r--  root root  Nov  : hello.c
 [root@standby gcc]# cat hello.c
 #include <stdio.h>
 int main(void)
 {
     printf("Hello World!\n");
     return ;
 }
 [root@standby gcc]#
 [root@standby gcc]# file hello.c
 hello.c: ASCII C program text
 [root@standby gcc]#

预处理/Preprocessing

'删除注释和";"、进行宏替换、将头文件插入进来、条件编译等'

 [root@standby gcc]# gcc -E hello.c -o hello.i
 [root@standby gcc]# ll
 total
 -rw-r--r--  root root     Nov  : hello.c
 -rw-r--r--  root root  Nov  : hello.i
 [root@standby gcc]# file hello.i
 hello.i: ASCII C program text
 [root@standby gcc]#

编译/Compilation

'生成汇编代码'

 [root@standby gcc]# gcc -S hello.i -o hello.s
 [root@standby gcc]# ll
 total
 -rw-r--r--  root root     Nov  : hello.c
 -rw-r--r--  root root  Nov  : hello.i
 -rw-r--r--  root root    Nov  : hello.s
 [root@standby gcc]# file hello.s
 hello.s: ASCII assembler program text
 [root@standby gcc]#

汇编/Assembly

'生成目标文件'

 [root@standby gcc]# gcc -c hello.s -o hello.o
 [root@standby gcc]# ll
 total
 -rw-r--r--  root root     Nov  : hello.c
 -rw-r--r--  root root  Nov  : hello.i
 -rw-r--r--  root root   Nov  : hello.o
 -rw-r--r--  root root    Nov  : hello.s
 [root@standby gcc]# file hello.o
 hello.o: ELF -bit LSB relocatable, x86-, version  (SYSV), not stripped
 [root@standby gcc]#

连接/Linking

'生成可执行文件'

 [root@standby gcc]# gcc hello.o -o helloworld
 [root@standby gcc]# ll
 total
 -rw-r--r--  root root     Nov  : hello.c
 -rw-r--r--  root root  Nov  : hello.i
 -rw-r--r--  root root   Nov  : hello.o
 -rw-r--r--  root root    Nov  : hello.s
 -rwxr-xr-x  root root   Nov  : helloworld
 [root@standby gcc]# file helloworld
 helloworld: ELF -bit LSB executable, x86-, version  (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6., not stripped
 [root@standby gcc]#
 [root@standby gcc]# ./helloworld
 Hello World!
 [root@standby gcc]#

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汇编代码

 [root@standby gcc]# cat hello.s
     .file    "hello.c"
     .section    .rodata
 .LC0:
     .string    "Hello World!"
     .text
 .globl main
     .type    main, @function
 main:
 .LFB0:
     .cfi_startproc
     pushq    %rbp
     .cfi_def_cfa_offset
     .cfi_offset , -
     movq    %rsp, %rbp
     .cfi_def_cfa_register
     movl    $.LC0, %edi
     call    puts
     movl    $, %eax
     leave
     .cfi_def_cfa ,
     ret
     .cfi_endproc
 .LFE0:
     .size    main, .-main
     .ident    "GCC: (GNU) 4.4.7 20120313 (Red Hat 4.4.7-17)"
     .section    .note.GNU-stack,"",@progbits
 [root@standby gcc]#