在C中，如何malloc和释放SOCKET（已经有一个指针）

Question

the SOCKET is from winsock.h

Declared as

SOCKET BillerSocket;

As far as I know SOCKET is already a pointer in disguise, so I shouldn't do free(*BillerSocket); .

I malloc it with

BillerSocket = malloc(sizeof(SOCKET));

I get this warning

[Warning] assignment makes integer from pointer without a cast [enabled by default]

When I free a SOCKET with

free(BillerSocket);

I get a warning and a Note which seems to tell me what I have to do.

[Warning] passing argument 1 of 'free' makes pointer from integer without a cast [enabled by default]

129 0   c:\program files\dev-cpp\mingw64\x86_64-w64-mingw32\include\combaseapi.h    In file included from c:\program files\dev-cpp\mingw64\x86_64-w64-mingw32\include\combaseapi.h
14      c:\program files\dev-cpp\mingw64\x86_64-w64-mingw32\include\objbase.h                    from c:\program files\dev-cpp\mingw64\x86_64-w64-mingw32\include\objbase.h
17      c:\program files\dev-cpp\mingw64\x86_64-w64-mingw32\include\ole2.h                   from c:\program files\dev-cpp\mingw64\x86_64-w64-mingw32\include\ole2.h
12      c:\program files\dev-cpp\mingw64\x86_64-w64-mingw32\include\wtypes.h                     from c:\program files\dev-cpp\mingw64\x86_64-w64-mingw32\include\wtypes.h
10      c:\program files\dev-cpp\mingw64\x86_64-w64-mingw32\include\winscard.h                   from c:\program files\dev-cpp\mingw64\x86_64-w64-mingw32\include\winscard.h
97      c:\program files\dev-cpp\mingw64\x86_64-w64-mingw32\include\windows.h                    from c:\program files\dev-cpp\mingw64\x86_64-w64-mingw32\include\windows.h
1       main.c       
            from main.c
438 16  c:\program files\dev-cpp\mingw64\x86_64-w64-mingw32\include\stdlib.h

[Note] expected 'void *' but argument is of type 'SOCKET'

How do I remove the warnings?

Answer 1

If you look at winsock.h more closely, you will see that SOCKET is not a pointer, it is an integer:

typedef UINT_PTR SOCKET;

UINT_PTR is not a pointer to a UINT ( PUINT and LPUINT are). It is a UINT that is the same size as a pointer. So UINT_PTR is 4 bytes in a 32bit process and is 8 bytes in a 64bit process. See MSDN's documentation for more details on that:

Windows Data Types

UINT_PTR
An unsigned INT_PTR.

This type is declared in BaseTsd.h as follows:

 #if defined(_WIN64) typedef unsigned __int64 UINT_PTR; #else typedef unsigned int UINT_PTR; #endif 

You do not use malloc() and free() to manage SOCKET values, you have to use socket() and closesocket() instead:

SOCKET BillerSocket;
...
BillerSocket = socket(...);
...
closesocket(BillerSocket);