CODEWITHSUNDEEP
c++11lambda
MiJia
MiJia

Reputation: 21

c++ lambda expression confusion

I feel confused about lambda in c++.Is it related to the compiler? The following code run correct in ubuntu g++ 4.6.3 and g++ 5.2. But when I run it in centos 4.8.5,the result is error.

// 
class ScopeGuard
{
 public:
    explicit ScopeGuard(std::function<void ()> onExitScope)
      :onExitScope_(onExitScope)
 {

 }

   ~ScopeGuard()
  {
     onExitScope_();
  }
private:
  std::function<void ()> onExitScope_;
};

And there is a function to uncompress the data.

//
...
int dstLen = 10 * 1024 * 1024;
char *dstBuf = new char[dstLen];
// When I comment this line the err return Z_OK, otherwise return Z_BUFF_ERROR.
ScopeGuard guard([&](){if (dstBuf) delete[] dstBuf; dstBuf=NULL;});

// zlib function. 
int err = uncompress((Bytef *)dstBuf, (uLongf*)&dstLen, (Bytef*)src, fileLen);

if (err != Z_OK)
{
    cout<<"uncompress error..."<<err<<endl;
    return false;
}`

Upvotes: 0

Views: 83

Answers (1)

Sebastian Redl
Sebastian Redl

Reputation: 72215

This is most likely because of this: (uLongf*)&dstLen.

dstLen is an int, which is 32 bits and all current typical systems. uLongf, however, is an alias for unsigned long, which is 32 bits on Windows and 32-bit *nix systems, but 64 bits on 64-bit *nix systems.

It is not safe, and likely to do the wrong thing, to cast an int* to an uLongf*.

The solution is to make dstLen an uLongf and remove the cast.

Upvotes: 1

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