从helloworld看程序的编译与链接

从hello world看程序的编译与链接

众所周知，程序的编译分为四个阶段，分别为预处理、编译、汇编与链接。以下从一个简单的hello world剖析程序的编译过程。

image-20230911164028023

1. 程序的编译与链接

源代码：

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// @file: test.c
#include<stdio.h>
int main() {
	printf("hello world\n");
	return 0;
}

预处理

处理源代码中以#开始的预编译指令，如#include、#define等。

gcc编译器对应程序：cc1

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gcc -E ./test.c -o ./test.i
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@file: test.i

# 1 "./test.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 31 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 32 "<command-line>" 2
# 1 "./test.c"
# 1 "/usr/include/stdio.h" 1 3 4
# 27 "/usr/include/stdio.h" 3 4
# 1 "/usr/include/x86_64-linux-gnu/bits/libc-header-start.h" 1 3 4
# 33 "/usr/include/x86_64-linux-gnu/bits/libc-header-start.h" 3 4
# 1 "/usr/include/features.h" 1 3 4
# 461 "/usr/include/features.h" 3 4
# 1 "/usr/include/x86_64-linux-gnu/sys/cdefs.h" 1 3 4
# 452 "/usr/include/x86_64-linux-gnu/sys/cdefs.h" 3 4
# 1 "/usr/include/x86_64-linux-gnu/bits/wordsize.h" 1 3 4
# 453 "/usr/include/x86_64-linux-gnu/sys/cdefs.h" 2 3 4
# 1 "/usr/include/x86_64-linux-gnu/bits/long-double.h" 1 3 4
# 454 "/usr/include/x86_64-linux-gnu/sys/cdefs.h" 2 3 4
# 462 "/usr/include/features.h" 2 3 4
# 485 "/usr/include/features.h" 3 4
# 1 "/usr/include/x86_64-linux-gnu/gnu/stubs.h" 1 3 4
# 10 "/usr/include/x86_64-linux-gnu/gnu/stubs.h" 3 4
# 1 "/usr/include/x86_64-linux-gnu/gnu/stubs-64.h" 1 3 4
# 11 "/usr/include/x86_64-linux-gnu/gnu/stubs.h" 2 3 4
# 486 "/usr/include/features.h" 2 3 4
# 34 "/usr/include/x86_64-linux-gnu/bits/libc-header-start.h" 2 3 4
# 28 "/usr/include/stdio.h" 2 3 4
......

编译

编译过程即将预处理后的文件进行一系列的词法分析、语法分析、语义分析以及优化，之后生成相应的汇编代码。

gcc编译器对应程序：cc1

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gcc -S test.i -o test.s
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@file: test.s
	
	.file	"test.c"
	.text
	.section	.rodata
.LC0:
	.string	"hello world"
	.text
	.globl	main
	.type	main, @function
main:
.LFB0:
	.cfi_startproc
	endbr64
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	leaq	.LC0(%rip), %rdi
	call	puts@PLT
	movl	$0, %eax
	popq	%rbp
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE0:
	.size	main, .-main
	.ident	"GCC: (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0"
	.section	.note.GNU-stack,"",@progbits
	.section	.note.gnu.property,"a"
	.align 8
	.long	 1f - 0f
	.long	 4f - 1f
	.long	 5
0:
	.string	 "GNU"
1:
	.align 8
	.long	 0xc0000002
	.long	 3f - 2f
2:
	.long	 0x3
3:
	.align 8
4:

汇编

将汇编指令转变为机器指令。

gcc编译器对应程序：as

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gcc -c test.s -o test.o

使用readelf -a ./test.o读取目标文件

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@file: test.o

ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              REL (Relocatable file)
  Machine:                           Advanced Micro Devices X86-64
  Version:                           0x1
  Entry point address:               0x0
  Start of program headers:          0 (bytes into file)
  Start of section headers:          784 (bytes into file)
  Flags:                             0x0
  Size of this header:               64 (bytes)
  Size of program headers:           0 (bytes)
  Number of program headers:         0
  Size of section headers:           64 (bytes)
  Number of section headers:         14
  Section header string table index: 13

Section Headers:
  [Nr] Name              Type             Address           Offset
       Size              EntSize          Flags  Link  Info  Align
  [ 0]                   NULL             0000000000000000  00000000
       0000000000000000  0000000000000000           0     0     0
  [ 1] .text             PROGBITS         0000000000000000  00000040
       000000000000001b  0000000000000000  AX       0     0     1
  [ 2] .rela.text        RELA             0000000000000000  00000250
       0000000000000030  0000000000000018   I      11     1     8
  [ 3] .data             PROGBITS         0000000000000000  0000005b
       0000000000000000  0000000000000000  WA       0     0     1
  [ 4] .bss              NOBITS           0000000000000000  0000005b
       0000000000000000  0000000000000000  WA       0     0     1
  [ 5] .rodata           PROGBITS         0000000000000000  0000005b
       000000000000000c  0000000000000000   A       0     0     1
  [ 6] .comment          PROGBITS         0000000000000000  00000067
       000000000000002c  0000000000000001  MS       0     0     1
  [ 7] .note.GNU-stack   PROGBITS         0000000000000000  00000093
       0000000000000000  0000000000000000           0     0     1
  [ 8] .note.gnu.propert NOTE             0000000000000000  00000098
       0000000000000020  0000000000000000   A       0     0     8
  [ 9] .eh_frame         PROGBITS         0000000000000000  000000b8
       0000000000000038  0000000000000000   A       0     0     8
  [10] .rela.eh_frame    RELA             0000000000000000  00000280
       0000000000000018  0000000000000018   I      11     9     8
  [11] .symtab           SYMTAB           0000000000000000  000000f0
       0000000000000138  0000000000000018          12    10     8
  [12] .strtab           STRTAB           0000000000000000  00000228
       0000000000000028  0000000000000000           0     0     1
  [13] .shstrtab         STRTAB           0000000000000000  00000298
       0000000000000074  0000000000000000           0     0     1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
  L (link order), O (extra OS processing required), G (group), T (TLS),
  C (compressed), x (unknown), o (OS specific), E (exclude),
  l (large), p (processor specific)

There are no section groups in this file.

There are no program headers in this file.

There is no dynamic section in this file.

Relocation section '.rela.text' at offset 0x250 contains 2 entries:
  Offset          Info           Type           Sym. Value    Sym. Name + Addend
00000000000b  000500000002 R_X86_64_PC32     0000000000000000 .rodata - 4
000000000010  000c00000004 R_X86_64_PLT32    0000000000000000 puts - 4

Relocation section '.rela.eh_frame' at offset 0x280 contains 1 entry:
  Offset          Info           Type           Sym. Value    Sym. Name + Addend
000000000020  000200000002 R_X86_64_PC32     0000000000000000 .text + 0

The decoding of unwind sections for machine type Advanced Micro Devices X86-64 is not currently supported.
# 现在符号表的地址值都是0
Symbol table '.symtab' contains 13 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
     1: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS test.c
     2: 0000000000000000     0 SECTION LOCAL  DEFAULT    1 
     3: 0000000000000000     0 SECTION LOCAL  DEFAULT    3 
     4: 0000000000000000     0 SECTION LOCAL  DEFAULT    4 
     5: 0000000000000000     0 SECTION LOCAL  DEFAULT    5 
     6: 0000000000000000     0 SECTION LOCAL  DEFAULT    7 
     7: 0000000000000000     0 SECTION LOCAL  DEFAULT    8 
     8: 0000000000000000     0 SECTION LOCAL  DEFAULT    9 
     9: 0000000000000000     0 SECTION LOCAL  DEFAULT    6 
    10: 0000000000000000    27 FUNC    GLOBAL DEFAULT    1 main
    11: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT  UND _GLOBAL_OFFSET_TABLE_
    12: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT  UND puts

No version information found in this file.

Displaying notes found in: .note.gnu.property
  Owner                Data size 	Description
  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
      Properties: x86 feature: IBT, SHSTK

file ./test.o输出

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./test.o: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped

链接

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gcc ./test.o -o ./test

使用readelf -a ./test读取目标文件

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ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              DYN (Shared object file)
  Machine:                           Advanced Micro Devices X86-64
  Version:                           0x1
  Entry point address:               0x1060
  Start of program headers:          64 (bytes into file)
  Start of section headers:          14712 (bytes into file)
  Flags:                             0x0
  Size of this header:               64 (bytes)
  Size of program headers:           56 (bytes)
  Number of program headers:         13
  Size of section headers:           64 (bytes)
  Number of section headers:         31
  Section header string table index: 30

Section Headers:
  [Nr] Name              Type             Address           Offset
       Size              EntSize          Flags  Link  Info  Align
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       0000000000000000  0000000000000000           0     0     0
  [ 1] .interp           PROGBITS         0000000000000318  00000318
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       000000000000000e  0000000000000002   A       6     0     2
  [ 9] .gnu.version_r    VERNEED          0000000000000500  00000500
       0000000000000020  0000000000000000   A       7     1     8
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  [15] .plt.sec          PROGBITS         0000000000001050  00001050
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  [20] .eh_frame         PROGBITS         0000000000002058  00002058
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  [21] .init_array       INIT_ARRAY       0000000000003db8  00002db8
       0000000000000008  0000000000000008  WA       0     0     8
  [22] .fini_array       FINI_ARRAY       0000000000003dc0  00002dc0
       0000000000000008  0000000000000008  WA       0     0     8
  [23] .dynamic          DYNAMIC          0000000000003dc8  00002dc8
       00000000000001f0  0000000000000010  WA       7     0     8
  [24] .got              PROGBITS         0000000000003fb8  00002fb8
       0000000000000048  0000000000000008  WA       0     0     8
  [25] .data             PROGBITS         0000000000004000  00003000
       0000000000000010  0000000000000000  WA       0     0     8
  [26] .bss              NOBITS           0000000000004010  00003010
       0000000000000008  0000000000000000  WA       0     0     1
  [27] .comment          PROGBITS         0000000000000000  00003010
       000000000000002b  0000000000000001  MS       0     0     1
  [28] .symtab           SYMTAB           0000000000000000  00003040
       0000000000000618  0000000000000018          29    46     8
  [29] .strtab           STRTAB           0000000000000000  00003658
       0000000000000202  0000000000000000           0     0     1
  [30] .shstrtab         STRTAB           0000000000000000  0000385a
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Key to Flags:
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  l (large), p (processor specific)

There are no section groups in this file.

Program Headers:
  Type           Offset             VirtAddr           PhysAddr
                 FileSiz            MemSiz              Flags  Align
  PHDR           0x0000000000000040 0x0000000000000040 0x0000000000000040
                 0x00000000000002d8 0x00000000000002d8  R      0x8
  INTERP         0x0000000000000318 0x0000000000000318 0x0000000000000318
                 0x000000000000001c 0x000000000000001c  R      0x1
      [Requesting program interpreter: /lib64/ld-linux-x86-64.so.2]
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x00000000000005f8 0x00000000000005f8  R      0x1000
  LOAD           0x0000000000001000 0x0000000000001000 0x0000000000001000
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  LOAD           0x0000000000002000 0x0000000000002000 0x0000000000002000
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  LOAD           0x0000000000002db8 0x0000000000003db8 0x0000000000003db8
                 0x0000000000000258 0x0000000000000260  RW     0x1000
  DYNAMIC        0x0000000000002dc8 0x0000000000003dc8 0x0000000000003dc8
                 0x00000000000001f0 0x00000000000001f0  RW     0x8
  NOTE           0x0000000000000338 0x0000000000000338 0x0000000000000338
                 0x0000000000000020 0x0000000000000020  R      0x8
  NOTE           0x0000000000000358 0x0000000000000358 0x0000000000000358
                 0x0000000000000044 0x0000000000000044  R      0x4
  GNU_PROPERTY   0x0000000000000338 0x0000000000000338 0x0000000000000338
                 0x0000000000000020 0x0000000000000020  R      0x8
  GNU_EH_FRAME   0x0000000000002010 0x0000000000002010 0x0000000000002010
                 0x0000000000000044 0x0000000000000044  R      0x4
  GNU_STACK      0x0000000000000000 0x0000000000000000 0x0000000000000000
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  GNU_RELRO      0x0000000000002db8 0x0000000000003db8 0x0000000000003db8
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 Section to Segment mapping:
  Segment Sections...
   00     
   01     .interp 
   02     .interp .note.gnu.property .note.gnu.build-id .note.ABI-tag .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt 
   03     .init .plt .plt.got .plt.sec .text .fini 
   04     .rodata .eh_frame_hdr .eh_frame 
   05     .init_array .fini_array .dynamic .got .data .bss 
   06     .dynamic 
   07     .note.gnu.property 
   08     .note.gnu.build-id .note.ABI-tag 
   09     .note.gnu.property 
   10     .eh_frame_hdr 
   11     
   12     .init_array .fini_array .dynamic .got 

Dynamic section at offset 0x2dc8 contains 27 entries:
  Tag        Type                         Name/Value
 0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]
 0x000000000000000c (INIT)               0x1000
 0x000000000000000d (FINI)               0x11e8
 0x0000000000000019 (INIT_ARRAY)         0x3db8
 0x000000000000001b (INIT_ARRAYSZ)       8 (bytes)
 0x000000000000001a (FINI_ARRAY)         0x3dc0
 0x000000000000001c (FINI_ARRAYSZ)       8 (bytes)
 0x000000006ffffef5 (GNU_HASH)           0x3a0
 0x0000000000000005 (STRTAB)             0x470
 0x0000000000000006 (SYMTAB)             0x3c8
 0x000000000000000a (STRSZ)              130 (bytes)
 0x000000000000000b (SYMENT)             24 (bytes)
 0x0000000000000015 (DEBUG)              0x0
 0x0000000000000003 (PLTGOT)             0x3fb8
 0x0000000000000002 (PLTRELSZ)           24 (bytes)
 0x0000000000000014 (PLTREL)             RELA
 0x0000000000000017 (JMPREL)             0x5e0
 0x0000000000000007 (RELA)               0x520
 0x0000000000000008 (RELASZ)             192 (bytes)
 0x0000000000000009 (RELAENT)            24 (bytes)
 0x000000000000001e (FLAGS)              BIND_NOW
 0x000000006ffffffb (FLAGS_1)            Flags: NOW PIE
 0x000000006ffffffe (VERNEED)            0x500
 0x000000006fffffff (VERNEEDNUM)         1
 0x000000006ffffff0 (VERSYM)             0x4f2
 0x000000006ffffff9 (RELACOUNT)          3
 0x0000000000000000 (NULL)               0x0

Relocation section '.rela.dyn' at offset 0x520 contains 8 entries:
  Offset          Info           Type           Sym. Value    Sym. Name + Addend
000000003db8  000000000008 R_X86_64_RELATIVE                    1140
000000003dc0  000000000008 R_X86_64_RELATIVE                    1100
000000004008  000000000008 R_X86_64_RELATIVE                    4008
000000003fd8  000100000006 R_X86_64_GLOB_DAT 0000000000000000 _ITM_deregisterTMClone + 0
000000003fe0  000300000006 R_X86_64_GLOB_DAT 0000000000000000 __libc_start_main@GLIBC_2.2.5 + 0
000000003fe8  000400000006 R_X86_64_GLOB_DAT 0000000000000000 __gmon_start__ + 0
000000003ff0  000500000006 R_X86_64_GLOB_DAT 0000000000000000 _ITM_registerTMCloneTa + 0
000000003ff8  000600000006 R_X86_64_GLOB_DAT 0000000000000000 __cxa_finalize@GLIBC_2.2.5 + 0

Relocation section '.rela.plt' at offset 0x5e0 contains 1 entry:
  Offset          Info           Type           Sym. Value    Sym. Name + Addend
000000003fd0  000200000007 R_X86_64_JUMP_SLO 0000000000000000 puts@GLIBC_2.2.5 + 0

The decoding of unwind sections for machine type Advanced Micro Devices X86-64 is not currently supported.

Symbol table '.dynsym' contains 7 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
     1: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND _ITM_deregisterTMCloneTab
     2: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND puts@GLIBC_2.2.5 (2)
     3: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __libc_start_main@GLIBC_2.2.5 (2)
     4: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND __gmon_start__
     5: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND _ITM_registerTMCloneTable
     6: 0000000000000000     0 FUNC    WEAK   DEFAULT  UND __cxa_finalize@GLIBC_2.2.5 (2)
# 现在符号表的地址值不空了
Symbol table '.symtab' contains 65 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
     1: 0000000000000318     0 SECTION LOCAL  DEFAULT    1 
     2: 0000000000000338     0 SECTION LOCAL  DEFAULT    2 
     3: 0000000000000358     0 SECTION LOCAL  DEFAULT    3 
     4: 000000000000037c     0 SECTION LOCAL  DEFAULT    4 
     5: 00000000000003a0     0 SECTION LOCAL  DEFAULT    5 
     6: 00000000000003c8     0 SECTION LOCAL  DEFAULT    6 
     7: 0000000000000470     0 SECTION LOCAL  DEFAULT    7 
     8: 00000000000004f2     0 SECTION LOCAL  DEFAULT    8 
     9: 0000000000000500     0 SECTION LOCAL  DEFAULT    9 
    10: 0000000000000520     0 SECTION LOCAL  DEFAULT   10 
    11: 00000000000005e0     0 SECTION LOCAL  DEFAULT   11 
    12: 0000000000001000     0 SECTION LOCAL  DEFAULT   12 
    13: 0000000000001020     0 SECTION LOCAL  DEFAULT   13 
    14: 0000000000001040     0 SECTION LOCAL  DEFAULT   14 
    15: 0000000000001050     0 SECTION LOCAL  DEFAULT   15 
    16: 0000000000001060     0 SECTION LOCAL  DEFAULT   16 
    17: 00000000000011e8     0 SECTION LOCAL  DEFAULT   17 
    18: 0000000000002000     0 SECTION LOCAL  DEFAULT   18 
    19: 0000000000002010     0 SECTION LOCAL  DEFAULT   19 
    20: 0000000000002058     0 SECTION LOCAL  DEFAULT   20 
    21: 0000000000003db8     0 SECTION LOCAL  DEFAULT   21 
    22: 0000000000003dc0     0 SECTION LOCAL  DEFAULT   22 
    23: 0000000000003dc8     0 SECTION LOCAL  DEFAULT   23 
    24: 0000000000003fb8     0 SECTION LOCAL  DEFAULT   24 
    25: 0000000000004000     0 SECTION LOCAL  DEFAULT   25 
    26: 0000000000004010     0 SECTION LOCAL  DEFAULT   26 
    27: 0000000000000000     0 SECTION LOCAL  DEFAULT   27 
    28: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS crtstuff.c
    29: 0000000000001090     0 FUNC    LOCAL  DEFAULT   16 deregister_tm_clones
    30: 00000000000010c0     0 FUNC    LOCAL  DEFAULT   16 register_tm_clones
    31: 0000000000001100     0 FUNC    LOCAL  DEFAULT   16 __do_global_dtors_aux
    32: 0000000000004010     1 OBJECT  LOCAL  DEFAULT   26 completed.8061
    33: 0000000000003dc0     0 OBJECT  LOCAL  DEFAULT   22 __do_global_dtors_aux_fin
    34: 0000000000001140     0 FUNC    LOCAL  DEFAULT   16 frame_dummy
    35: 0000000000003db8     0 OBJECT  LOCAL  DEFAULT   21 __frame_dummy_init_array_
    36: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS test.c
    37: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS crtstuff.c
    38: 000000000000215c     0 OBJECT  LOCAL  DEFAULT   20 __FRAME_END__
    39: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS 
    40: 0000000000003dc0     0 NOTYPE  LOCAL  DEFAULT   21 __init_array_end
    41: 0000000000003dc8     0 OBJECT  LOCAL  DEFAULT   23 _DYNAMIC
    42: 0000000000003db8     0 NOTYPE  LOCAL  DEFAULT   21 __init_array_start
    43: 0000000000002010     0 NOTYPE  LOCAL  DEFAULT   19 __GNU_EH_FRAME_HDR
    44: 0000000000003fb8     0 OBJECT  LOCAL  DEFAULT   24 _GLOBAL_OFFSET_TABLE_
    45: 0000000000001000     0 FUNC    LOCAL  DEFAULT   12 _init
    46: 00000000000011e0     5 FUNC    GLOBAL DEFAULT   16 __libc_csu_fini
    47: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND _ITM_deregisterTMCloneTab
    48: 0000000000004000     0 NOTYPE  WEAK   DEFAULT   25 data_start
    49: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND puts@@GLIBC_2.2.5
    50: 0000000000004010     0 NOTYPE  GLOBAL DEFAULT   25 _edata
    51: 00000000000011e8     0 FUNC    GLOBAL HIDDEN    17 _fini
    52: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __libc_start_main@@GLIBC_
    53: 0000000000004000     0 NOTYPE  GLOBAL DEFAULT   25 __data_start
    54: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND __gmon_start__
    55: 0000000000004008     0 OBJECT  GLOBAL HIDDEN    25 __dso_handle
    56: 0000000000002000     4 OBJECT  GLOBAL DEFAULT   18 _IO_stdin_used
    57: 0000000000001170   101 FUNC    GLOBAL DEFAULT   16 __libc_csu_init
    58: 0000000000004018     0 NOTYPE  GLOBAL DEFAULT   26 _end
    59: 0000000000001060    47 FUNC    GLOBAL DEFAULT   16 _start
    60: 0000000000004010     0 NOTYPE  GLOBAL DEFAULT   26 __bss_start
    61: 0000000000001149    27 FUNC    GLOBAL DEFAULT   16 main
    62: 0000000000004010     0 OBJECT  GLOBAL HIDDEN    25 __TMC_END__
    63: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND _ITM_registerTMCloneTable
    64: 0000000000000000     0 FUNC    WEAK   DEFAULT  UND __cxa_finalize@@GLIBC_2.2

Histogram for `.gnu.hash' bucket list length (total of 2 buckets):
 Length  Number     % of total  Coverage
      0  1          ( 50.0%)
      1  1          ( 50.0%)    100.0%

Version symbols section '.gnu.version' contains 7 entries:
 Addr: 0x00000000000004f2  Offset: 0x0004f2  Link: 6 (.dynsym)
  000:   0 (*local*)       0 (*local*)       2 (GLIBC_2.2.5)   2 (GLIBC_2.2.5)
  004:   0 (*local*)       0 (*local*)       2 (GLIBC_2.2.5)

Version needs section '.gnu.version_r' contains 1 entry:
 Addr: 0x0000000000000500  Offset: 0x000500  Link: 7 (.dynstr)
  000000: Version: 1  File: libc.so.6  Cnt: 1
  0x0010:   Name: GLIBC_2.2.5  Flags: none  Version: 2

Displaying notes found in: .note.gnu.property
  Owner                Data size 	Description
  GNU                  0x00000010	NT_GNU_PROPERTY_TYPE_0
      Properties: x86 feature: IBT, SHSTK

Displaying notes found in: .note.gnu.build-id
  Owner                Data size 	Description
  GNU                  0x00000014	NT_GNU_BUILD_ID (unique build ID bitstring)
    Build ID: 1fbbe46df4a06904e20ce722c19cfdfcd468895d

Displaying notes found in: .note.ABI-tag
  Owner                Data size 	Description
  GNU                  0x00000010	NT_GNU_ABI_TAG (ABI version tag)
    OS: Linux, ABI: 3.2.0

2. 关于ELF格式

程序源代码编译后分为以下两种段：

  • 程序指令

    • .text段

      执行语句的机器代码

  • 程序数据

    • .data段

      初始化的全局变量和局部静态变量

    • .bss段

      未初始化的全局变量和局部静态变量。.bss段这是为未初始化的全局变量与局部静态变量预留位置，并没有内容，所以在文件中也不占据空间。

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# 查看ELF文件的代码段、数据段和BSS段长度
size ./test
#    text	   data	    bss	    dec	    hex	filename
#    1565	    600	      8	   2173	    87d	./test

# 查看目标文件的结构与内容
objdump -h ./test

# 使用nm查看符号
nm ./test
# 输出
    0000000000004010 B __bss_start
    0000000000004010 b completed.8061
                     w __cxa_finalize@@GLIBC_2.2.5
    0000000000004000 D __data_start
	# ......

3. 参考文档

《程序员的自我修养—链接、装载与库》

4. 补充知识

  • 关于ABI与API

符号修饰标准、变量内存布局以及函数调用方式等这些与可执行代码二进制兼容性相关的内容成为ABI。API与ABI实际都是应用程序接口，只不过描述的层面不一样。

API一般是源代码级别的接口，而ABI指的是二进制层面的接口。

注意，API相同并不代表ABI相同。

  • 为什么说C++的ABI兼容性差？

ChatGPT：

C++的ABI兼容性差主要是由于以下两个原因：

  1. 名称修饰方式不统一：不同编译器可能会有不同的名称修饰方式，即对于同一个函数名，不同编译器生成的二进制代码可能不同，导致链接时无法找到符号。解决这个问题的方法就是要求所有编译器都使用同样的名称修饰方式。
  2. 类的布局方式不统一：在 C++ 中，类的内存布局方式由编译器决定，这取决于编译器对于虚函数表的管理方式、对于空类、单继承或多继承类的内存分布等等。如果不同的编译器使用不同的布局方式，则在链接时就会出现链接错误或者难以调试的问题。因此，为了解决这个问题，需要对 C++ 的类进行 ABI 规范，如 Itanium C++ ABI，它规定了 C++ 的类的布局方式，从而使得在使用不同编译器编译的代码可以进行链接和调用。

由于 C++ 语言的发展越来越快，加上 C++ 语言的语法繁多，导致 C++ 的标准版本和编译器的版本之间在 ABI 兼容性方面存在较大的问题，这也让 C++ 的 ABI 兼容性变得很差。因此，如果要在不同平台之间共享 C++ 库，需要注意 ABI 兼容性问题。

#原创 #计算机科学
从helloworld看程序的编译与链接
http://ziyangfu.github.io/2023/05/06/从helloworld看程序的编译与链接/
作者
FZY
发布于
2023年5月6日
许可协议