关于valgrind的 “Conditional jump or move depends on uninitialised value(s)”

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转载最新推荐文章于 2023-12-17 17:35:58 发布 · 1.2k 阅读

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原文链接：http://www.cnblogs.com/FrankTan/archive/2010/01/08/1642569.html

本文探讨了Valgrind在特定条件下可能产生的误报问题，通过一个实例代码演示了即使存在Conditional jump or move depends on uninitialised value(s)警告，程序也可能正常运行且无实际bug的情况。文章强调了在遇到此类警告时，开发者需要仔细分析代码逻辑，判断警告是否真正指向潜在的问题。

关于valgrind的 “Conditional jump or move depends on uninitialised value(s)”：

valgrind在报这个错误的时候程序未必有bug，如下例：

代码

//test.cpp
#include <iostream>
using namespace std;
bool ptr(char *testptr)
{
        int i=0;
        if(i == 0){
                memcpy(testptr,"Hello",5);
                return true;
        }
        return false;
}

int main(int argc, const char *argv[])
{
        char *p = new char [10];
        if(ptr(p)){
                printf("%s\n",p);
        }

        delete [] p;

        return 0;
}

执行：
g++ test.cpp -Wall
valgrind --tool=memcheck --leak-check=full --show-reachable=yes ./a.out

就会报下面的错：

==8472==
==8472== Conditional jump or move depends on uninitialised value(s)
==8472==    at 0x4906507: strlen (mac_replace_strmem.c:243)
==8472==    by 0x3D26142A0A: vfprintf (in /lib64/tls/libc-2.3.4.so)
==8472==    by 0x3D26148157: printf (in /lib64/tls/libc-2.3.4.so)
==8472==    by 0x4009A6: main (in /home/maoqi/private/cpp/a.out)
Hello
==8472==
==8472== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 5 from 2)
==8472== malloc/free: in use at exit: 0 bytes in 0 blocks.
==8472== malloc/free: 1 allocs, 1 frees, 10 bytes allocated.
==8472== For counts of detected errors, rerun with: -v
==8472== All heap blocks were freed -- no leaks are possible.

因此在遇到这种错误的时候需要仔细分析。

转载于:https://www.cnblogs.com/FrankTan/archive/2010/01/08/1642569.html