Question

int main()  
{      
    char *p;  
    p = malloc(10);  
    delete(p);    
    return;  
}

Valgrind检测到什么是适当的错误？

Answer 1

首先，此代码段提供了两个编译错误，

在函数'int main（）'中：错误：从'void *'到'char *'的无效转换[-fpermissive] p = malloc（10）;
^ 错误：没有值的return语句，函数返回'int'[ - fpermissive] 返回;
使用这些更改更正代码，
- 使用malloc分配内存时进行类型转换，如下所示。 p =（char *）malloc（10）;
- main函数的返回类型是int，因此请相应地更改返回值，如此处所述。返回0; //使用return 0，而不仅仅是return。
- 在使用删除操作之前，请对指针进行有效性检查，如下所示。如果（P）删除（P）;
通过上述更改，并成功编译上述代码。使用valgrind工具运行上面的示例。因此代码中没有问题，所以valgrind没有发现任何问题。下面是示例valgrind输出。

Valgrind输出：

==30050== Memcheck, a memory error detector
==30050== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==30050== Using Valgrind-3.12.0 and LibVEX; rerun with -h for copyright info
==30050== Command: ./valgrindtest
==30050== 
main Start
==30050== Mismatched free() / delete / delete []
==30050==    at 0x4C2C18D: operator delete(void*) (vg_replace_malloc.c:576)
==30050==    by 0x4006E0: main (valgrindtest.cpp:16)
==30050==  Address 0x5a1b040 is 0 bytes inside a block of size 10 alloc'd
==30050==    at 0x4C2ABE3: malloc (vg_replace_malloc.c:299)
==30050==    by 0x4006C2: main (valgrindtest.cpp:11)
==30050== 
main End
==30050== 
==30050== HEAP SUMMARY:
==30050==     in use at exit: 0 bytes in 0 blocks
==30050==   total heap usage: 1 allocs, 1 frees, 10 bytes allocated
==30050== 
==30050== All heap blocks were freed -- no leaks are possible
==30050== 
==30050== For counts of detected and suppressed errors, rerun with: -v
==30050== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

适用于GDB的Valgrind工具

1 个答案: