When I create an asm file of my program in ARM the GCC sometimes does not generate the function epilogue in the function itself, but instead it creates some labels and then call the label for function epilogue. This is only happening in the assembly code and then later linker fix it. Is there anyway to force the assembler code to generate .s files that do not put function epilogue in the labels?
Example when I compile the c code to assembly with -S switch:
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}
Here is the disassembly of FunctionX:
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
As you can see the L7 is actually the one that holds the function epilogue for the FunctionX. Once I compile the code to binary, it will be in its correct form (function epilogue at the end of the function) as you can see at address 0x10e34. But is it possible to have the same form in the assembly code too (when I compile the source file to asm using -S switch) and force the gcc to not make the labels for function epilogue?
.L7is still there:10d10: ea000040 b 10e18 < FunctionX +0x190>. Also note that the B instruction isn't a call instruction, it's a simple unconditional branch (jump). - Ross Ridgeb .L7goes away which is probably what your main concern is (aside for the mis-understandings). - artless noise