C++之调试内存访问错误(二百一十一)

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1.前言

本篇目的：理解C++之调试内存访问错误手段。

2.内存访问越界例子

1 #include <cstdio>
2 
3 int main(void) {
4   int a[5] = {0};
5   //访问数组索引5,越界.
6   a[5] = 2;
7 
8   printf("%d\n", a[5]);
9   return 0;
10 }

编译：g++ -fsanitize=address test.cpp -g -o test
运行: ./test

=================================================================
==269033==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffeaa98aae4 at pc 0x55978dd8839a bp 0x7ffeaa98aaa0 sp 0x7ffeaa98aa90
WRITE of size 4 at 0x7ffeaa98aae4 thread T0
    #0 0x55978dd88399 in main ~/test.cpp:6
    #1 0x7f8010ea5d8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
    #2 0x7f8010ea5e3f in __libc_start_main_impl ../csu/libc-start.c:392
    #3 0x55978dd88184 in _start (~/test+0x1184)

Address 0x7ffeaa98aae4 is located in stack of thread T0 at offset 52 in frame
    #0 0x55978dd88258 in main ~/test.cpp:3

  This frame has 1 object(s):
    [32, 52) 'a' (line 4) <== Memory access at offset 52 overflows this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism, swapcontext or vfork
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow ~/test.cpp:6 in main
Shadow bytes around the buggy address:
  0x100055529500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100055529510: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100055529520: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100055529530: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100055529540: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x100055529550: 00 00 00 00 00 00 f1 f1 f1 f1 00 00[04]f3 f3 f3
  0x100055529560: f3 f3 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100055529570: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100055529580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x100055529590: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1000555295a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
  Shadow gap:              cc
==269033==ABORTING

SUMMARY: AddressSanitizer: stack-buffer-overflow ~/test.cpp:6 in main
第6行内存溢出， 访问数组索引5越界，导致内存溢出。