How does a UNICODE environment block look like to start a new process via CreateProcessW() on Windows?

Question

Essentially, I would like to create a new process and define the environment for it from the parent process. I would like to use CreateProcessW and pass a (modified) UNICODE environment into lpEnvironment, but I'm not sure what the content should look like compared to an ANSII environment block.

The only documentation I really found is on MSDN:

Note that an ANSI environment block is terminated by two zero bytes: one for the last string, one more to terminate the block. A Unicode environment block is terminated by four zero bytes: two for the last string, two more to terminate the block.

Now I tried to

1. call GetEnvironmentStrings and pass it on to the child process
2. call GetEnvironmentStringsW and pass it to the child process
3. modify these blocks with my additional environment strings and pass it on

non of them work

I really only could set lpEnvironment to NULL to get it to work, but now I would have to change & revert my parents processing environment - is that the way to go here?

(I also did set CREATE_UNICODE_ENVIRONMENT)

Could anyone please tell me what is so special about UNICODE environment blocks - it did work, when I just use ASCII stuff and call CreateProcessA()...

Answer 1

I have no idea what you are doing wrong without code. But this works:

STARTUPINFO startInfo = {0};
PROCESS_INFORMATION procInfo = {0};

WCHAR env[] = L"key=value\0key2=value2\0\0";
WCHAR cmdline[] = L"calc";

startInfo.cb = sizeof(startInfo);
if(!CreateProcessW(NULL, cmdline, NULL, NULL, FALSE, CREATE_UNICODE_ENVIRONMENT, env, NULL, &startInfo, &procInfo))
{
    printf("Error %d\n", GetLastError());
}

Perhaps that will give you an idea of what you are doing wrong.