mirror of
https://github.com/pkivolowitz/asm_book.git
synced 2026-06-21 01:46:46 +08:00
added description of const variables
This commit is contained in:
Perry Kivolowitz
parent
c76f9cf931
commit
b0e7f86154
5 changed files with 970 additions and 1 deletions
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@ -61,7 +61,8 @@ the 64 bit ARM Instruction Set Architecture (ISA).
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| .... a | [.... Alignment](./section_1/structs/alignment.md) |
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| .... b | [.... Defining](./section_1/structs/defining.md) |
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| .... c | [.... Using](./section_1/structs/using.md) |
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| 8 | [Casting](./section_1/casting/README.md) |
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| 8 | [`const`](./section1/const/README.md)
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| 9 | [Casting](./section_1/casting/README.md) |
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## Section 2 - Stuff
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117
section_1/const/README.md
Normal file
117
section_1/const/README.md
Normal file
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@ -0,0 +1,117 @@
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# Section 1 / `const`
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In C++, a variable declared to be const cannot be altered.
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This concept only *partially* translates to assembly language
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in a manner which is enforced by the hardware. The remainder
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of the functionality of `const` is enforced at compile time
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and therefore, at the assembly language level, all bets are
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off.
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## What Is **Not** Enforced
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Given [this](./const_test.cpp) short C++ snippet:
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```c++
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#include <stdio.h> // 1
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// 2
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void Const1() { // 3
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const int foo = 9; // 4
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printf("%d\n", foo); // 5
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} // 6
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```
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it is the C++ compiler that enforces the immutable nature of `foo`.
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Looking at the assembly language that is produced from this C++ code,
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you will [see](./const_test.s) that `foo` is implemented like any other
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variable. Once
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in assembly language you are behind the defenses of the compiler so
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to speak. You can modify a `const` local variable or parameter to your
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heart's content. Should you? That's another question. Will it cause harm?
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It depends.
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## What **IS** Enforced
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Let's examine [this](./rodata.s) code:
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```text
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.global main // 1
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.align 2 // 2
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// 3
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.section .rodata // 4
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rotypo: .asciz "Rypo" // Meant this to be "Typo" // 5
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fmt: .asciz "%s\n" // Used to print the strings // 6
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// 7
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.data // 8
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rwtypo: .asciz "Rypo" // Meant this to be "Typo" // 9
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// 10
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.text // 11
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// 12
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main: str x30, [sp, -16]! // 13
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// Try to fix rwtypo --- this will work // 14
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ldr x1, =rwtypo // 15
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mov w2, 'T' // 16
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strb w2, [x1] // 17
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ldr x0, =fmt // Notice I already loaded rwtypo // 18
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bl printf // 19
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// 20
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// Try to fix rotypo --- this will end in tears // 21
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ldr x1, =rotypo // 22
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mov w2, 'T' // 23
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strb w2, [x1] // 24
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ldr x0, =fmt // Notice I already loaded rotypo // 25
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bl printf // 26
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// 27
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ldr x30, [sp], 16 // 28
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mov w0, wzr // 29
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ret // 30
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// 31
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.end // 32
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// 33
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```
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In this example, we are declaring a `const` *global variable*.
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Notice `.section .rodata`. This assembler directive tells the linker to place
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what follows into memory that will be marked as read only. Any attempt to
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modify something marked as read only by the hardware will result in a crash.
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`rwtypo` can be read and written as it is located after a `.data`. The
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string contains a typo - we meant to write "Typo" but we experienced a
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senior moment and what got entered was "Rypo". Could happen to anyone.
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For some reason, we will fix "Rypo", turning it into "Type" using code
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rather than simply editing the file.
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The same is true for `rotypo`. Extra credit for being consistent.
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However,
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`rotypo` is going to live in a region of memory marked as read only
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at the hardware level because it is defined after a `.section .rodata`.
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Will we be able to correct it using code?
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tl;dr Nope.
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This program, when run, will produce the following output:
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```text
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const > ./a.out
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Typo
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Segmentation fault (core dumped)
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const >
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```
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This demonstrates that the first attempt at modifying `rwtypo` worked. And
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then, an attempt to modify `rotypo` causes a segmentation fault.
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## Summary
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The meaning and function of `const` only partially translates
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to assembly language. `const` local variables and `const`
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parameters are just like any other data to assembly language.
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The constant nature of `const` local variables and parameters
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is implemented solely in the compiler.
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`const` globals are made constant by the hardware. Attempting
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to modify a variable protected in this manner will be like
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poking a dragon. Best not to poke dragons.
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6
section_1/const/const_test.cpp
Normal file
6
section_1/const/const_test.cpp
Normal file
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@ -0,0 +1,6 @@
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#include <stdio.h>
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void Const1() {
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const int foo = 9;
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printf("%d\n", foo);
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}
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812
section_1/const/const_test.s
Normal file
812
section_1/const/const_test.s
Normal file
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@ -0,0 +1,812 @@
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.arch armv8-a
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.file "const_test.cpp"
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.text
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.Ltext0:
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.section .rodata
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.align 3
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.LC0:
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.string "%d\n"
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.text
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.align 2
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.global _Z6Const1v
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.type _Z6Const1v, %function
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_Z6Const1v:
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.LFB0:
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.file 1 "const_test.cpp"
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.loc 1 3 15
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.cfi_startproc
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stp x29, x30, [sp, -32]!
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.cfi_def_cfa_offset 32
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.cfi_offset 29, -32
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.cfi_offset 30, -24
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mov x29, sp
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.loc 1 4 12
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mov w0, 9 // LOOK HERE - the value of 9 goes
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str w0, [sp, 28] // onto the stack - this is `foo`.
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.loc 1 5 8
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mov w1, 9
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adrp x0, .LC0
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add x0, x0, :lo12:.LC0
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bl printf
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.loc 1 6 1
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nop
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ldp x29, x30, [sp], 32
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.cfi_restore 30
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.cfi_restore 29
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.cfi_def_cfa_offset 0
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ret
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.cfi_endproc
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.LFE0:
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.size _Z6Const1v, .-_Z6Const1v
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.Letext0:
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.file 2 "/usr/lib/gcc/aarch64-linux-gnu/9/include/stddef.h"
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.file 3 "/usr/include/aarch64-linux-gnu/bits/types.h"
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.file 4 "/usr/include/aarch64-linux-gnu/bits/types/struct_FILE.h"
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.file 5 "/usr/include/aarch64-linux-gnu/bits/types/FILE.h"
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.file 6 "/usr/include/stdio.h"
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.file 7 "/usr/include/aarch64-linux-gnu/bits/sys_errlist.h"
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.section .debug_info,"",@progbits
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.Ldebug_info0:
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.4byte 0x325
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.2byte 0x4
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.4byte .Ldebug_abbrev0
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.byte 0x8
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.uleb128 0x1
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.4byte .LASF51
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.byte 0x4
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.4byte .LASF52
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.4byte .LASF53
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.8byte .Ltext0
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.8byte .Letext0-.Ltext0
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.4byte .Ldebug_line0
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.uleb128 0x2
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.4byte .LASF7
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.byte 0x2
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.byte 0xd1
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.byte 0x17
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.4byte 0x39
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.uleb128 0x3
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.byte 0x8
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.byte 0x7
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.4byte .LASF0
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.uleb128 0x4
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.byte 0x8
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.uleb128 0x5
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.byte 0x4
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.byte 0x5
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.string "int"
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.uleb128 0x6
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.4byte 0x42
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.uleb128 0x3
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.byte 0x1
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.byte 0x8
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.4byte .LASF1
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.uleb128 0x3
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.byte 0x2
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.byte 0x7
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.4byte .LASF2
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.uleb128 0x3
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.byte 0x4
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.byte 0x7
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.4byte .LASF3
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.uleb128 0x3
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.byte 0x1
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.byte 0x6
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.4byte .LASF4
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.uleb128 0x3
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.byte 0x2
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.byte 0x5
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.4byte .LASF5
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.uleb128 0x3
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.byte 0x8
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.byte 0x5
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.4byte .LASF6
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.uleb128 0x2
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.4byte .LASF8
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.byte 0x3
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.byte 0x98
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.byte 0x19
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.4byte 0x71
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.uleb128 0x2
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.4byte .LASF9
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.byte 0x3
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.byte 0x99
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.byte 0x1b
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.4byte 0x71
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.uleb128 0x7
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.byte 0x8
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.4byte 0x96
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.uleb128 0x3
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.byte 0x1
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.byte 0x8
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.4byte .LASF10
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.uleb128 0x6
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.4byte 0x96
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.uleb128 0x8
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.4byte .LASF54
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.byte 0xd8
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.byte 0x4
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.byte 0x31
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.byte 0x8
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.4byte 0x229
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.uleb128 0x9
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.4byte .LASF11
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.byte 0x4
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.byte 0x33
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.byte 0x7
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.4byte 0x42
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.byte 0
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.uleb128 0x9
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.4byte .LASF12
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.byte 0x4
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.byte 0x36
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.byte 0x9
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.4byte 0x90
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.byte 0x8
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.uleb128 0x9
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.4byte .LASF13
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.byte 0x4
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.byte 0x37
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.byte 0x9
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.4byte 0x90
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.byte 0x10
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.uleb128 0x9
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.4byte .LASF14
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.byte 0x4
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.byte 0x38
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.byte 0x9
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.4byte 0x90
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.byte 0x18
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.uleb128 0x9
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.4byte .LASF15
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.byte 0x4
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.byte 0x39
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.byte 0x9
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.4byte 0x90
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.byte 0x20
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.uleb128 0x9
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.4byte .LASF16
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.byte 0x4
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.byte 0x3a
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.byte 0x9
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.4byte 0x90
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.byte 0x28
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.uleb128 0x9
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.4byte .LASF17
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.byte 0x4
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.byte 0x3b
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.byte 0x9
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.4byte 0x90
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.byte 0x30
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.uleb128 0x9
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.4byte .LASF18
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.byte 0x4
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.byte 0x3c
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.byte 0x9
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.4byte 0x90
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.byte 0x38
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.uleb128 0x9
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.4byte .LASF19
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.byte 0x4
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.byte 0x3d
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.byte 0x9
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.4byte 0x90
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.byte 0x40
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.uleb128 0x9
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.4byte .LASF20
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.byte 0x4
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.byte 0x40
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.byte 0x9
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.4byte 0x90
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.byte 0x48
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.uleb128 0x9
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.4byte .LASF21
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.byte 0x4
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.byte 0x41
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.byte 0x9
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.4byte 0x90
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.byte 0x50
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.uleb128 0x9
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.4byte .LASF22
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.byte 0x4
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.byte 0x42
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.byte 0x9
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.4byte 0x90
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.byte 0x58
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.uleb128 0x9
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.4byte .LASF23
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.byte 0x4
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.byte 0x44
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.byte 0x16
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.4byte 0x242
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.byte 0x60
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.uleb128 0x9
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.4byte .LASF24
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.byte 0x4
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.byte 0x46
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.byte 0x14
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.4byte 0x248
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.byte 0x68
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.uleb128 0x9
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.4byte .LASF25
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.byte 0x4
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.byte 0x48
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||||
.byte 0x7
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.4byte 0x42
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||||
.byte 0x70
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.uleb128 0x9
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.4byte .LASF26
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.byte 0x4
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.byte 0x49
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||||
.byte 0x7
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||||
.4byte 0x42
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.byte 0x74
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.uleb128 0x9
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.4byte .LASF27
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.byte 0x4
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.byte 0x4a
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||||
.byte 0xb
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.4byte 0x78
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.byte 0x78
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.uleb128 0x9
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.4byte .LASF28
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.byte 0x4
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.byte 0x4d
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.byte 0x12
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.4byte 0x55
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.byte 0x80
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.uleb128 0x9
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.4byte .LASF29
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.byte 0x4
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||||
.byte 0x4e
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.byte 0xf
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.4byte 0x63
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.byte 0x82
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.uleb128 0x9
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.4byte .LASF30
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.byte 0x4
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.byte 0x4f
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.byte 0x8
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||||
.4byte 0x24e
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.byte 0x83
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||||
.uleb128 0x9
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||||
.4byte .LASF31
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||||
.byte 0x4
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||||
.byte 0x51
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||||
.byte 0xf
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||||
.4byte 0x25e
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||||
.byte 0x88
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||||
.uleb128 0x9
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||||
.4byte .LASF32
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||||
.byte 0x4
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||||
.byte 0x59
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||||
.byte 0xd
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||||
.4byte 0x84
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||||
.byte 0x90
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||||
.uleb128 0x9
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||||
.4byte .LASF33
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||||
.byte 0x4
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||||
.byte 0x5b
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||||
.byte 0x17
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||||
.4byte 0x269
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||||
.byte 0x98
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||||
.uleb128 0x9
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||||
.4byte .LASF34
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||||
.byte 0x4
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||||
.byte 0x5c
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||||
.byte 0x19
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||||
.4byte 0x274
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||||
.byte 0xa0
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||||
.uleb128 0x9
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||||
.4byte .LASF35
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||||
.byte 0x4
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||||
.byte 0x5d
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||||
.byte 0x14
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||||
.4byte 0x248
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||||
.byte 0xa8
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||||
.uleb128 0x9
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||||
.4byte .LASF36
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||||
.byte 0x4
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||||
.byte 0x5e
|
||||
.byte 0x9
|
||||
.4byte 0x40
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||||
.byte 0xb0
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||||
.uleb128 0x9
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||||
.4byte .LASF37
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||||
.byte 0x4
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||||
.byte 0x5f
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||||
.byte 0xa
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||||
.4byte 0x2d
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||||
.byte 0xb8
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||||
.uleb128 0x9
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.4byte .LASF38
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||||
.byte 0x4
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||||
.byte 0x60
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||||
.byte 0x7
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||||
.4byte 0x42
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.byte 0xc0
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.uleb128 0x9
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.4byte .LASF39
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||||
.byte 0x4
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||||
.byte 0x62
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||||
.byte 0x8
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||||
.4byte 0x27a
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||||
.byte 0xc4
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.byte 0
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||||
.uleb128 0x2
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.4byte .LASF40
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||||
.byte 0x5
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||||
.byte 0x7
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||||
.byte 0x19
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||||
.4byte 0xa2
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.uleb128 0xa
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.4byte .LASF55
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||||
.byte 0x4
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||||
.byte 0x2b
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||||
.byte 0xe
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.uleb128 0xb
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.4byte .LASF41
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.uleb128 0x7
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.byte 0x8
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.4byte 0x23d
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.uleb128 0x7
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.byte 0x8
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||||
.4byte 0xa2
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.uleb128 0xc
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.4byte 0x96
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.4byte 0x25e
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.uleb128 0xd
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.4byte 0x39
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.byte 0
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||||
.byte 0
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||||
.uleb128 0x7
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.byte 0x8
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||||
.4byte 0x235
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.uleb128 0xb
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.4byte .LASF42
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.uleb128 0x7
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.byte 0x8
|
||||
.4byte 0x264
|
||||
.uleb128 0xb
|
||||
.4byte .LASF43
|
||||
.uleb128 0x7
|
||||
.byte 0x8
|
||||
.4byte 0x26f
|
||||
.uleb128 0xc
|
||||
.4byte 0x96
|
||||
.4byte 0x28a
|
||||
.uleb128 0xd
|
||||
.4byte 0x39
|
||||
.byte 0x13
|
||||
.byte 0
|
||||
.uleb128 0x7
|
||||
.byte 0x8
|
||||
.4byte 0x9d
|
||||
.uleb128 0x6
|
||||
.4byte 0x28a
|
||||
.uleb128 0xe
|
||||
.4byte .LASF44
|
||||
.byte 0x6
|
||||
.byte 0x89
|
||||
.byte 0xe
|
||||
.4byte 0x2a1
|
||||
.uleb128 0x7
|
||||
.byte 0x8
|
||||
.4byte 0x229
|
||||
.uleb128 0xe
|
||||
.4byte .LASF45
|
||||
.byte 0x6
|
||||
.byte 0x8a
|
||||
.byte 0xe
|
||||
.4byte 0x2a1
|
||||
.uleb128 0xe
|
||||
.4byte .LASF46
|
||||
.byte 0x6
|
||||
.byte 0x8b
|
||||
.byte 0xe
|
||||
.4byte 0x2a1
|
||||
.uleb128 0xe
|
||||
.4byte .LASF47
|
||||
.byte 0x7
|
||||
.byte 0x1a
|
||||
.byte 0xc
|
||||
.4byte 0x42
|
||||
.uleb128 0xc
|
||||
.4byte 0x290
|
||||
.4byte 0x2d6
|
||||
.uleb128 0xf
|
||||
.byte 0
|
||||
.uleb128 0xe
|
||||
.4byte .LASF48
|
||||
.byte 0x7
|
||||
.byte 0x1b
|
||||
.byte 0x1a
|
||||
.4byte 0x2cb
|
||||
.uleb128 0xe
|
||||
.4byte .LASF49
|
||||
.byte 0x7
|
||||
.byte 0x1e
|
||||
.byte 0xc
|
||||
.4byte 0x42
|
||||
.uleb128 0xe
|
||||
.4byte .LASF50
|
||||
.byte 0x7
|
||||
.byte 0x1f
|
||||
.byte 0x1a
|
||||
.4byte 0x2cb
|
||||
.uleb128 0x10
|
||||
.4byte .LASF56
|
||||
.byte 0x1
|
||||
.byte 0x3
|
||||
.byte 0x6
|
||||
.4byte .LASF57
|
||||
.8byte .LFB0
|
||||
.8byte .LFE0-.LFB0
|
||||
.uleb128 0x1
|
||||
.byte 0x9c
|
||||
.uleb128 0x11
|
||||
.string "foo"
|
||||
.byte 0x1
|
||||
.byte 0x4
|
||||
.byte 0xc
|
||||
.4byte 0x49
|
||||
.uleb128 0x2
|
||||
.byte 0x91
|
||||
.sleb128 -4
|
||||
.byte 0
|
||||
.byte 0
|
||||
.section .debug_abbrev,"",@progbits
|
||||
.Ldebug_abbrev0:
|
||||
.uleb128 0x1
|
||||
.uleb128 0x11
|
||||
.byte 0x1
|
||||
.uleb128 0x25
|
||||
.uleb128 0xe
|
||||
.uleb128 0x13
|
||||
.uleb128 0xb
|
||||
.uleb128 0x3
|
||||
.uleb128 0xe
|
||||
.uleb128 0x1b
|
||||
.uleb128 0xe
|
||||
.uleb128 0x11
|
||||
.uleb128 0x1
|
||||
.uleb128 0x12
|
||||
.uleb128 0x7
|
||||
.uleb128 0x10
|
||||
.uleb128 0x17
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0x2
|
||||
.uleb128 0x16
|
||||
.byte 0
|
||||
.uleb128 0x3
|
||||
.uleb128 0xe
|
||||
.uleb128 0x3a
|
||||
.uleb128 0xb
|
||||
.uleb128 0x3b
|
||||
.uleb128 0xb
|
||||
.uleb128 0x39
|
||||
.uleb128 0xb
|
||||
.uleb128 0x49
|
||||
.uleb128 0x13
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0x3
|
||||
.uleb128 0x24
|
||||
.byte 0
|
||||
.uleb128 0xb
|
||||
.uleb128 0xb
|
||||
.uleb128 0x3e
|
||||
.uleb128 0xb
|
||||
.uleb128 0x3
|
||||
.uleb128 0xe
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0x4
|
||||
.uleb128 0xf
|
||||
.byte 0
|
||||
.uleb128 0xb
|
||||
.uleb128 0xb
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0x5
|
||||
.uleb128 0x24
|
||||
.byte 0
|
||||
.uleb128 0xb
|
||||
.uleb128 0xb
|
||||
.uleb128 0x3e
|
||||
.uleb128 0xb
|
||||
.uleb128 0x3
|
||||
.uleb128 0x8
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0x6
|
||||
.uleb128 0x26
|
||||
.byte 0
|
||||
.uleb128 0x49
|
||||
.uleb128 0x13
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0x7
|
||||
.uleb128 0xf
|
||||
.byte 0
|
||||
.uleb128 0xb
|
||||
.uleb128 0xb
|
||||
.uleb128 0x49
|
||||
.uleb128 0x13
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0x8
|
||||
.uleb128 0x13
|
||||
.byte 0x1
|
||||
.uleb128 0x3
|
||||
.uleb128 0xe
|
||||
.uleb128 0xb
|
||||
.uleb128 0xb
|
||||
.uleb128 0x3a
|
||||
.uleb128 0xb
|
||||
.uleb128 0x3b
|
||||
.uleb128 0xb
|
||||
.uleb128 0x39
|
||||
.uleb128 0xb
|
||||
.uleb128 0x1
|
||||
.uleb128 0x13
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0x9
|
||||
.uleb128 0xd
|
||||
.byte 0
|
||||
.uleb128 0x3
|
||||
.uleb128 0xe
|
||||
.uleb128 0x3a
|
||||
.uleb128 0xb
|
||||
.uleb128 0x3b
|
||||
.uleb128 0xb
|
||||
.uleb128 0x39
|
||||
.uleb128 0xb
|
||||
.uleb128 0x49
|
||||
.uleb128 0x13
|
||||
.uleb128 0x38
|
||||
.uleb128 0xb
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0xa
|
||||
.uleb128 0x16
|
||||
.byte 0
|
||||
.uleb128 0x3
|
||||
.uleb128 0xe
|
||||
.uleb128 0x3a
|
||||
.uleb128 0xb
|
||||
.uleb128 0x3b
|
||||
.uleb128 0xb
|
||||
.uleb128 0x39
|
||||
.uleb128 0xb
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0xb
|
||||
.uleb128 0x13
|
||||
.byte 0
|
||||
.uleb128 0x3
|
||||
.uleb128 0xe
|
||||
.uleb128 0x3c
|
||||
.uleb128 0x19
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0xc
|
||||
.uleb128 0x1
|
||||
.byte 0x1
|
||||
.uleb128 0x49
|
||||
.uleb128 0x13
|
||||
.uleb128 0x1
|
||||
.uleb128 0x13
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0xd
|
||||
.uleb128 0x21
|
||||
.byte 0
|
||||
.uleb128 0x49
|
||||
.uleb128 0x13
|
||||
.uleb128 0x2f
|
||||
.uleb128 0xb
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0xe
|
||||
.uleb128 0x34
|
||||
.byte 0
|
||||
.uleb128 0x3
|
||||
.uleb128 0xe
|
||||
.uleb128 0x3a
|
||||
.uleb128 0xb
|
||||
.uleb128 0x3b
|
||||
.uleb128 0xb
|
||||
.uleb128 0x39
|
||||
.uleb128 0xb
|
||||
.uleb128 0x49
|
||||
.uleb128 0x13
|
||||
.uleb128 0x3f
|
||||
.uleb128 0x19
|
||||
.uleb128 0x3c
|
||||
.uleb128 0x19
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0xf
|
||||
.uleb128 0x21
|
||||
.byte 0
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0x10
|
||||
.uleb128 0x2e
|
||||
.byte 0x1
|
||||
.uleb128 0x3f
|
||||
.uleb128 0x19
|
||||
.uleb128 0x3
|
||||
.uleb128 0xe
|
||||
.uleb128 0x3a
|
||||
.uleb128 0xb
|
||||
.uleb128 0x3b
|
||||
.uleb128 0xb
|
||||
.uleb128 0x39
|
||||
.uleb128 0xb
|
||||
.uleb128 0x6e
|
||||
.uleb128 0xe
|
||||
.uleb128 0x11
|
||||
.uleb128 0x1
|
||||
.uleb128 0x12
|
||||
.uleb128 0x7
|
||||
.uleb128 0x40
|
||||
.uleb128 0x18
|
||||
.uleb128 0x2116
|
||||
.uleb128 0x19
|
||||
.byte 0
|
||||
.byte 0
|
||||
.uleb128 0x11
|
||||
.uleb128 0x34
|
||||
.byte 0
|
||||
.uleb128 0x3
|
||||
.uleb128 0x8
|
||||
.uleb128 0x3a
|
||||
.uleb128 0xb
|
||||
.uleb128 0x3b
|
||||
.uleb128 0xb
|
||||
.uleb128 0x39
|
||||
.uleb128 0xb
|
||||
.uleb128 0x49
|
||||
.uleb128 0x13
|
||||
.uleb128 0x2
|
||||
.uleb128 0x18
|
||||
.byte 0
|
||||
.byte 0
|
||||
.byte 0
|
||||
.section .debug_aranges,"",@progbits
|
||||
.4byte 0x2c
|
||||
.2byte 0x2
|
||||
.4byte .Ldebug_info0
|
||||
.byte 0x8
|
||||
.byte 0
|
||||
.2byte 0
|
||||
.2byte 0
|
||||
.8byte .Ltext0
|
||||
.8byte .Letext0-.Ltext0
|
||||
.8byte 0
|
||||
.8byte 0
|
||||
.section .debug_line,"",@progbits
|
||||
.Ldebug_line0:
|
||||
.section .debug_str,"MS",@progbits,1
|
||||
.LASF19:
|
||||
.string "_IO_buf_end"
|
||||
.LASF27:
|
||||
.string "_old_offset"
|
||||
.LASF47:
|
||||
.string "sys_nerr"
|
||||
.LASF22:
|
||||
.string "_IO_save_end"
|
||||
.LASF5:
|
||||
.string "short int"
|
||||
.LASF7:
|
||||
.string "size_t"
|
||||
.LASF32:
|
||||
.string "_offset"
|
||||
.LASF16:
|
||||
.string "_IO_write_ptr"
|
||||
.LASF11:
|
||||
.string "_flags"
|
||||
.LASF18:
|
||||
.string "_IO_buf_base"
|
||||
.LASF23:
|
||||
.string "_markers"
|
||||
.LASF13:
|
||||
.string "_IO_read_end"
|
||||
.LASF36:
|
||||
.string "_freeres_buf"
|
||||
.LASF57:
|
||||
.string "_Z6Const1v"
|
||||
.LASF50:
|
||||
.string "_sys_errlist"
|
||||
.LASF46:
|
||||
.string "stderr"
|
||||
.LASF51:
|
||||
.string "GNU C++14 9.4.0 -mlittle-endian -mabi=lp64 -g -fasynchronous-unwind-tables -fstack-protector-strong -fstack-clash-protection"
|
||||
.LASF31:
|
||||
.string "_lock"
|
||||
.LASF6:
|
||||
.string "long int"
|
||||
.LASF28:
|
||||
.string "_cur_column"
|
||||
.LASF49:
|
||||
.string "_sys_nerr"
|
||||
.LASF29:
|
||||
.string "_vtable_offset"
|
||||
.LASF54:
|
||||
.string "_IO_FILE"
|
||||
.LASF1:
|
||||
.string "unsigned char"
|
||||
.LASF4:
|
||||
.string "signed char"
|
||||
.LASF33:
|
||||
.string "_codecvt"
|
||||
.LASF3:
|
||||
.string "unsigned int"
|
||||
.LASF41:
|
||||
.string "_IO_marker"
|
||||
.LASF30:
|
||||
.string "_shortbuf"
|
||||
.LASF15:
|
||||
.string "_IO_write_base"
|
||||
.LASF39:
|
||||
.string "_unused2"
|
||||
.LASF12:
|
||||
.string "_IO_read_ptr"
|
||||
.LASF2:
|
||||
.string "short unsigned int"
|
||||
.LASF10:
|
||||
.string "char"
|
||||
.LASF56:
|
||||
.string "Const1"
|
||||
.LASF34:
|
||||
.string "_wide_data"
|
||||
.LASF35:
|
||||
.string "_freeres_list"
|
||||
.LASF37:
|
||||
.string "__pad5"
|
||||
.LASF42:
|
||||
.string "_IO_codecvt"
|
||||
.LASF0:
|
||||
.string "long unsigned int"
|
||||
.LASF17:
|
||||
.string "_IO_write_end"
|
||||
.LASF9:
|
||||
.string "__off64_t"
|
||||
.LASF8:
|
||||
.string "__off_t"
|
||||
.LASF24:
|
||||
.string "_chain"
|
||||
.LASF43:
|
||||
.string "_IO_wide_data"
|
||||
.LASF52:
|
||||
.string "const_test.cpp"
|
||||
.LASF21:
|
||||
.string "_IO_backup_base"
|
||||
.LASF44:
|
||||
.string "stdin"
|
||||
.LASF26:
|
||||
.string "_flags2"
|
||||
.LASF38:
|
||||
.string "_mode"
|
||||
.LASF14:
|
||||
.string "_IO_read_base"
|
||||
.LASF53:
|
||||
.string "/media/psf/Home/Documents/asm_book/section_1/const"
|
||||
.LASF20:
|
||||
.string "_IO_save_base"
|
||||
.LASF48:
|
||||
.string "sys_errlist"
|
||||
.LASF25:
|
||||
.string "_fileno"
|
||||
.LASF40:
|
||||
.string "FILE"
|
||||
.LASF45:
|
||||
.string "stdout"
|
||||
.LASF55:
|
||||
.string "_IO_lock_t"
|
||||
.ident "GCC: (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0"
|
||||
.section .note.GNU-stack,"",@progbits
|
||||
33
section_1/const/rodata.s
Normal file
33
section_1/const/rodata.s
Normal file
|
|
@ -0,0 +1,33 @@
|
|||
.global main
|
||||
.align 2
|
||||
|
||||
.section .rodata
|
||||
rotypo: .asciz "Rypo" // Meant this to be "Typo"
|
||||
fmt: .asciz "%s\n" // Used to print the strings
|
||||
|
||||
.data
|
||||
rwtypo: .asciz "Rypo" // Meant this to be "Typo"
|
||||
|
||||
.text
|
||||
|
||||
main: str x30, [sp, -16]!
|
||||
// Try to fix rwtypo --- this will work
|
||||
ldr x1, =rwtypo
|
||||
mov w2, 'T'
|
||||
strb w2, [x1]
|
||||
ldr x0, =fmt // Notice I already loaded rwtypo
|
||||
bl printf
|
||||
|
||||
// Try to fix rotypo --- this will end in tears
|
||||
ldr x1, =rotypo
|
||||
mov w2, 'T'
|
||||
strb w2, [x1]
|
||||
ldr x0, =fmt // Notice I already loaded rwtypo
|
||||
bl printf
|
||||
|
||||
ldr x30, [sp], 16
|
||||
mov w0, wzr
|
||||
ret
|
||||
|
||||
.end
|
||||
|
||||
Loading…
Reference in a new issue