I am trying to upload a file to a PHP page using WinInet. I'm getting an Access Violation on one of the functions, but can't see why. I've built the code from an example page.

Here is the code:

HINTERNET aInternet=InternetOpen("My-Custom-Agent/1.0",INTERNET_OPEN_TYPE_DIRECT,NULL,NULL,0);
HINTERNET aConnect=InternetConnect(aInternet,"www.myserver.com",INTERNET_DEFAULT_HTTP_PORT, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 1);
if (aConnect)
{
    HINTERNET aRequest=HttpOpenRequest(aConnect, (const char*)"POST","myphppage.php", NULL, NULL, (const char**)"*/*\0",0,1);
    // ^^
    // Exception happens on this line
    // Exception thrown at 0x70C85B7C (ininet.dll) in TestApp.exe:
    // 0xC00000005: Access violation reading location 0x002A2F2A
    //
}

When I download from the server with InternetOpenURL(), everything seems fine. It just doesn't like what I'm doing somewhere here. Any clue what I'm doing wrong?

CodePudding user response：

Per the HttpOpenRequest() documentation:

[in] lplpszAcceptTypes

A pointer to a null-terminated array of strings that indicates media types accepted by the client. Here is an example.

PCTSTR rgpszAcceptTypes[] = {_T("text/*"), NULL};

Failing to properly terminate the array with a NULL pointer will cause a crash.

You are passing in a pointer to a single null-terminated string, incorrectly type-casted to const char**:

lplpszAcceptTypes -> "*/*"

But the function requires a pointer to an array of pointers to null-terminated strings:

                     -----
lplpszAcceptTypes -> | 0 | -> "*/*"
                     |---|
                     | 1 | -> NULL
                     -----

See the difference? So, the function misinterprets the contents of your string literal as an array of pointers, which it is not, hence the AV crash.

Use this instead:

LPCSTR rgpszAcceptTypes[] = {"*/*", NULL};
HINTERNET aRequest = HttpOpenRequest(aConnect, "POST", "myphppage.php", NULL, NULL, rgpszAcceptTypes, 0, 1);