C++本地运行无误，Leetcode编译器报错：AddressSanitizer: heap-buffer-overflow on address

本文链接：https://blog.youkuaiyun.com/Ejzq1/article/details/128591772

文章描述了一个由AddressSanitizer检测到的内存缓冲区溢出问题，该问题源于代码中的数组访问越界。由于条件检查的顺序，程序在特定情况下会尝试读取无效地址。正确的解决方案是优化代码，确保先进行边界检查。

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报错提示：

=================================================================
==42==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000016 at pc 0x00000034bcbd bp 0x7ffe28a84fe0 sp 0x7ffe28a84fd8
READ of size 1 at 0x602000000016 thread T0
    #5 0x7fd0c747a082  (/lib/x86_64-linux-gnu/libc.so.6+0x24082)
0x602000000016 is located 0 bytes to the right of 6-byte region [0x602000000010,0x602000000016)
allocated by thread T0 here:
    #3 0x7fd0c747a082  (/lib/x86_64-linux-gnu/libc.so.6+0x24082)
Shadow bytes around the buggy address:
  0x0c047fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c047fff8000: fa fa[06]fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
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
==42==ABORTING

问题分析：

报错关键代码：

        
        if (visited[x * n + y]) return 0;
        if (!(x < m && y < n))return 0;
        if (numCal(x) + numCal(y) > k)return 0;

AddressSanitizer（ASan）是一个快速的内存错误检测工具。它非常快，只拖慢程序两倍左右。

应该就是内存泄漏问题，一般出现在数组越界访问之类的。

本地不报错的原因：
越界的值也能返回……

可以看到上述代码中，为了易读性，我把程序特殊情况挨着列出来，忘记了顺序问题，

如果写成：if (visited[x * n + y] || !(x < m && y < n) || numCal(x) + numCal(y) > k) return 0;

同样会报错，因为也是顺序执行的。

正确写法先判断if (!(x < m && y < n))return 0;