ERROR_INSUFFICIENT_BUFFER returned from GetAdaptersAddresses - c++

Question

Using the following code, more or less copy-pasted from the MSDN example of
GetAdaptersAddresses, I get the return value 122, which means ERROR_INSUFFICIENT_BUFFER (according to this system error code list).
ULONG outBufLen = 150000; // Tried for different (large) values here...
PIP_ADAPTER_ADDRESSES pAddresses = (IP_ADAPTER_ADDRESSES *) malloc(outBufLen);
DWORD dwRetVal = GetAdaptersAddresses(AF_INET, 0, NULL, pAddresses, &outBufLen);
// ....
free(pAddresses);
The documentation of GetAdaptersAddresses does not list ERROR_INSUFFICIENT_BUFFER as one of the expected return values. (It lists ERROR_BUFFER_OVERFLOW, which should adjust outBufLen to the needed value, but that remains unchanged).
Using GetAdaptersInfo instead leads to the same symptoms.
This error does not occur on my development machine, but on one virtual and one real clean Windows 7 x86 SP1 installation (added the VC++ redistributables).
As a c++ newbie, am I doing something wrong? What could cause this error and how to fix it? =)

Answer 1

First of all, you can - as others suggested - do two calls, to find out required buffer size, and then do the query itself. Especially if you are seeing the error, your first try would be to ask API what size it expected.
Second, you need to know that this API is not quite safe in 32-bit processes consuming high amounts of memory, so that buffers span into higher 2GB of address space. API might start acting in a weird way, either due to its own bug, or a bug in an underlying layer. See details on this on MS Connect here: GetAdaptersAddresses API incorrectly returns no adapters for a process with high memory consumption.
The fact that error code is not "one of the expected return values" tells for the versions that the error comes from an underlying layer and this API just passes it up on internal failure. As a clue, having disabled some network adapter on the system, you might get rid of the error.

Answer 2

Visual Studio deployed a library named "IPHLPAPI.dll" together with my project which caused the problem. Deleting this file solved it.
Why this was the case is subject to further research =)

Answer 3

First, a buffer is a block of memory.
So insufficient could mean that you haven't given it enough memory somehow. Our could be a block of memory which you don't have access to. Maybe the address doesn't even exist.
Look at this:
ERROR_INSUFFICIENT_BUFFER
122 (0x7A)
The data area passed to a system call is too small.
This sounds really like the buffer hasn't got enough allocated memory. Or similar.
Maybe the
outBufLen
has to be a specific length, maybe the size of the memory block. Because sometimes it doesn't check for the 'name' but tries to compare for each of the variables size. This idea came from the High Level Shader Language.
So i would try to look a bit more on the:
ULONG outBufLen = 150000; // Tried for different (large) values here...
PIP_ADAPTER_ADDRESSES pAddresses = (IP_ADAPTER_ADDRESSES *) malloc(outBufLen);
Good luck!

Answer 4

To know the exact buffer size required, you can just pass NULL into pAddresses and size will be set to the required size. You may want to rewrite your code slightly to make that work;
DWORD rv, size = 0;
PIP_ADAPTER_ADDRESSES adapter_addresses;
rv = GetAdaptersAddresses(AF_INET, 0, NULL, NULL, &size);
if (rv != ERROR_BUFFER_OVERFLOW)
return false; // ERROR
adapter_addresses = (PIP_ADAPTER_ADDRESSES)malloc(size);
rv = GetAdaptersAddresses(AF_INET, 0, NULL, adapter_addresses, &size);
if (rv != ERROR_SUCCESS) {
free(adapter_addresses);
return false; // ERROR
}