当我在ARM中创建我的程序的asm文件时，GCC有时不会在函数本身中生成函数结尾，而是创建一些标签，然后调用函数结尾的标签 . 这只发生在汇编代码中，然后链接器修复它 . 反正是否强制汇编程序代码生成.s文件，这些文件没有在标签中放置函数结尾？
使用-S开关将c代码编译为程序集时的示例：
FunctionX
stmfd sp!, {fp, lr}
add fp, sp, #4
sub sp, sp, #32
str r0, [fp, #-32]
ldr r3, .L19
sub ip, fp, #28
ldmia r3, {r0, r1, r2, r3}
stmia ip, {r0, r1, r2, r3}
mov r3, #0
str r3, [fp, #-8]
b .L8
.L8:
ldr r3, [fp, #-8]
cmp r3, #3
bls .L17
mov r0, r0 @ nop
.L17:
ldr r3, [fp, #-8]
mov r3, r3, asl #2
sub r2, fp, #4
add r3, r2, r3
ldr r3, [r3, #-24]
ldr r1, .L19+4
mov r0, r3
bl fopen
str r0, [fp, #-12]
ldr r3, [fp, #-12]
cmp r3, #0
bne .L9
ldr r3, [fp, #-8]
mov r3, r3, asl #2
sub r2, fp, #4
add r3, r2, r3
ldr r3, [r3, #-24]
mov r1, r3
ldr r0, .L19+8
bl printf
b .L7
.L7:
sub sp, fp, #4
@ sp needed
ldmfd sp!, {fp, pc}
这是 FunctionX 的反汇编：
00010c88 <FunctionX>:
10c88: e92d4800 push {fp, lr}
10c8c: e28db004 add fp, sp, #4
10c90: e24dd028 sub sp, sp, #40 ; 0x28
10c94: e50b0028 str r0, [fp, #-40] ; 0xffffffd8
10c98: e59f3198 ldr r3, [pc, #408] ; 10e38 <FunctionX+0x1b0>
10c9c: e5933000 ldr r3, [r3]
10ca0: e50b3008 str r3, [fp, #-8]
10ca4: e59f3190 ldr r3, [pc, #400] ; 10e3c <FunctionX>
10ca8: e24bc018 sub ip, fp, #24
10cac: e893000f ldm r3, {r0, r1, r2, r3}
10cb0: e88c000f stm ip, {r0, r1, r2, r3}
10cb4: e3a03000 mov r3, #0
10cb8: e50b3020 str r3, [fp, #-32] ; 0xffffffe0
10cbc: ea000051 b 10e08 <FunctionX+0x180>
10cc0: e51b3020 ldr r3, [fp, #-32] ; 0xffffffe0
10cc4: e1a03103 lsl r3, r3, #2
10cc8: e24b2004 sub r2, fp, #4
10ccc: e0823003 add r3, r2, r3
10cd0: e5133014 ldr r3, [r3, #-20] ; 0xffffffec
10cd4: e59f1164 ldr r1, [pc, #356] ; 10e40 < FunctionX +0x1b8>
10cd8: e1a00003 mov r0, r3
10cdc: ebffff01 bl 108e8 <fopen@plt>
10ce0: e50b001c str r0, [fp, #-28] ; 0xffffffe4
10ce4: e51b301c ldr r3, [fp, #-28] ; 0xffffffe4
10ce8: e3530000 cmp r3, #0
10cec: 1a000008 bne 10d14 < FunctionX +0x8c>
10cf0: e51b3020 ldr r3, [fp, #-32] ; 0xffffffe0
10cf4: e1a03103 lsl r3, r3, #2
10cf8: e24b2004 sub r2, fp, #4
10cfc: e0823003 add r3, r2, r3
10d00: e5133014 ldr r3, [r3, #-20] ; 0xffffffec
10d04: e1a01003 mov r1, r3
10d08: e59f0134 ldr r0, [pc, #308] ; 10e44 < FunctionX +0x1bc>
10d0c: ebfffef2 bl 108dc <printf@plt>
10d10: ea000040 b 10e18 < FunctionX +0x190>
10d14: e51b001c ldr r0, [fp, #-28] ; 0xffffffe4
10d18: ebffff1c bl 10990 <fileno@plt>
10d1c: e1a03000 mov r3, r0
10d20: e3a01002 mov r1, #2
10d24: e1a00003 mov r0, r3
10d28: ebffff0c bl 10960 <flock@plt>
10d2c: e51b3020 ldr r3, [fp, #-32] ; 0xffffffe0
10d30: e3530003 cmp r3, #3
10d34: 979ff103 ldrls pc, [pc, r3, lsl #2]
10d38: ea000027 b 10ddc <FunctionX+0x154>
10d3c: 00010d4c .word 0x00010d4c
10d40: 00010d70 .word 0x00010d70
10d44: 00010d94 .word 0x00010d94
10d48: 00010db8 .word 0x00010db8
10d4c: e51b3028 ldr r3, [fp, #-40] ; 0xffffffd8
10d50: e5930010 ldr r0, [r3, #16]
10d54: e51b3028 ldr r3, [fp, #-40] ; 0xffffffd8
10d58: e5933000 ldr r3, [r3]
10d5c: e1a02003 mov r2, r3
10d60: e51b301c ldr r3, [fp, #-28] ; 0xffffffe4
10d64: e3a01001 mov r1, #1
10d68: ebfffeea bl 10918 <fwrite@plt>
10d6c: ea00001a b 10ddc < FunctionX+0x154>
10d70: e51b3028 ldr r3, [fp, #-40] ; 0xffffffd8
10d74: e5930014 ldr r0, [r3, #20]
10d78: e51b3028 ldr r3, [fp, #-40] ; 0xffffffd8
10d7c: e5933004 ldr r3, [r3, #4]
10d80: e1a02003 mov r2, r3
10d84: e51b301c ldr r3, [fp, #-28] ; 0xffffffe4
10d88: e3a01001 mov r1, #1
10d8c: ebfffee1 bl 10918 <fwrite@plt>
10d90: ea000011 b 10ddc < FunctionX+0x154>
10d94: e51b3028 ldr r3, [fp, #-40] ; 0xffffffd8
10d98: e5930018 ldr r0, [r3, #24]
10d9c: e51b3028 ldr r3, [fp, #-40] ; 0xffffffd8
10da0: e5933008 ldr r3, [r3, #8]
10da4: e1a02003 mov r2, r3
10da8: e51b301c ldr r3, [fp, #-28] ; 0xffffffe4
10dac: e3a01002 mov r1, #2
10db0: ebfffed8 bl 10918 <fwrite@plt>
10db4: ea000008 b 10ddc < FunctionX+0x154>
10db8: e51b3028 ldr r3, [fp, #-40] ; 0xffffffd8
10dbc: e593001c ldr r0, [r3, #28]
10dc0: e51b3028 ldr r3, [fp, #-40] ; 0xffffffd8
10dc4: e593300c ldr r3, [r3, #12]
10dc8: e1a02003 mov r2, r3
10dcc: e51b301c ldr r3, [fp, #-28] ; 0xffffffe4
10dd0: e3a01002 mov r1, #2
10dd4: ebfffecf bl 10918 <fwrite@plt>
10dd8: e1a00000 nop ; (mov r0, r0)
10ddc: e51b001c ldr r0, [fp, #-28] ; 0xffffffe4
10de0: ebfffeea bl 10990 <fileno@plt>
10de4: e1a03000 mov r3, r0
10de8: e3a01008 mov r1, #8
10dec: e1a00003 mov r0, r3
10df0: ebfffeda bl 10960 <flock@plt>
10df4: e51b001c ldr r0, [fp, #-28] ; 0xffffffe4
10df8: ebfffee7 bl 1099c <fclose@plt>
10dfc: e51b3020 ldr r3, [fp, #-32] ; 0xffffffe0
10e00: e2833001 add r3, r3, #1
10e04: e50b3020 str r3, [fp, #-32] ; 0xffffffe0
10e08: e51b3020 ldr r3, [fp, #-32] ; 0xffffffe0
10e0c: e3530003 cmp r3, #3
10e10: 9affffaa bls 10cc0 <FunctionX+0x38>
10e14: e1a00000 nop ; (mov r0, r0)
10e18: e59f3018 ldr r3, [pc, #24] ; 10e38 <FunctionX+0x1b0>
10e1c: e51b2008 ldr r2, [fp, #-8]
10e20: e5933000 ldr r3, [r3]
10e24: e1520003 cmp r2, r3
10e28: 0a000000 beq 10e30 <FunctionX+0x1a8>
10e2c: ebfffeb6 bl 1090c <__stack_chk_fail@plt>
10e30: e24bd004 sub sp, fp, #4
10e34: e8bd8800 pop {fp, pc}
10e38: 00022008 .word 0x00022008
10e3c: 000110f4 .word 0x000110f4
10e40: 00011098 .word 0x00011098
10e44: 0001109c .word 0x0001109c
正如您所看到的， L7 实际上是持有 FunctionX 函数结尾的那个 . 一旦我将代码编译为二进制文件，它将以正确的形式（函数末尾的函数结尾），如地址0x10e34所示 . 但是也可以在汇编代码中使用相同的表单（当我使用 -S 开关将源文件编译为asm时）并强制gcc不为函数尾声制作标签？
1 回答
.L7是本地标签 . 它是函数中分支的跳转目标 . 正如@Ross指出的那样，.L7的分支只是b（跳转）指令，而不是bl（调用） .这些标签不是单独的功能，它们只是基本的块 .