How to get CreateProcess/CreateProcessW to execute a process in a path > MAX_PATH characters

Question

I'm trying to get either CreateProcess or CreateProcessW to execute a process with a name < MAX_PATH characters but in a path that's greater than MAX_PATH characters. According to the docs at: http://msdn.microsoft.com/en-us/library/ms682425.aspx, I need to make sure lpApplicationName isn't NULL and then lpCommandLine can be up to 32,768 characters.

I tried that, but I get ERROR_PATH_NOT_FOUND.

I changed to CreateProcessW, but still get the same error. When I prefix lpApplicationName with \\?\ as described in http://msdn.microsoft.com/en-us/library/aa365247(VS.85).aspx when calling CreateProcessW I get a different error that makes me think I'm a bit closer: ERROR_SXS_CANT_GEN_ACTCTX.

My call to CreateProcessW is:

CreateProcessW(w_argv0,arg_string,NULL,NULL,0,NULL,NULL,&si,&ipi);

where w_argv0 is \\?\<long absolute path>\foo.exe.

arg_string contains "<long absolute path>\foo.exe" foo

si is set as follows:

    memset(&si,0,sizeof(si));
    si.cb = sizeof(si);
    si.dwFlags = STARTF_USESHOWWINDOW;
    si.wShowWindow = SW_HIDE;>

and pi is empty, as in:

    memset(&pi,0,sizeof(pi));

I looked in the system event log and there's a new entry each time I try this with event id 59, source SideBySide: Generate Activation Context failed for .Manifest. Reference error message: The operation completed successfully.

The file I'm trying to execute runs fine in a path < MAX_PATH characters.

To clarify, no one component of <long absolute path> is greater than MAX_PATH characters. The name of the executable itself certainly isn't, even with .manifest on the end. But, the entire path together is greater than MAX_PATH characters long.

I get the same error whether I embed its manifest or not. The manifest is named foo.exe.manifest and lives in the same directory as the executable when it's not embedded. It contains:

<?xml version='1.0' encoding='UTF-8' standalone='yes'?>
<assembly xmlns='urn:schemas-microsoft-com:asm.v1' manifestVersion='1.0'>
  <dependency>
    <dependentAssembly>
      <assemblyIdentity type='win32' name='Microsoft.VC80.DebugCRT' version='8.0.50727.762' processorArchitecture='x86' publicKeyToken='1fc8b3b9a1e18e3b' />
    </dependentAssembly>
  </dependency>
</assembly>

Anyone know how to get this to work? Possibly:

• some other way to call CreateProcess or CreateProcessW to execute a process in a path > MAX_PATH characters

• something I can do in the manifest file

I'm building with Visual Studio 2005 on XP SP2 and running native.

Thanks for your help.

Answer 1

Embedding the manifest and using GetShortPathNameW did it for me. One or the other on their own wasn't enough.

Before calling CreateProcessW using the \\?-prefixed absolute path name of the process to execute as the first argument, I check:

wchar_t *w_argv0;
wchar_t *w_short_argv0;

...

if (wcslen(w_argv0) >= MAX_PATH)
{
    num_chars = GetShortPathNameW(w_argv0,NULL,0);
    if (num_chars == 0) {
        syslog(LOG_ERR,"GetShortPathName(%S) to get size failed (%d)",
               w_argv0,GetLastError());
        /*
        ** Might as well keep going and try with the long name
        */
    } else {
        w_short_argv0 = malloc(num_chars * sizeof(wchar_t));
        memset(w_short_argv0,0,num_chars * sizeof(wchar_t));
        if (GetShortPathNameW(w_argv0,w_short_argv0,num_chars) == 0) {
            syslog(LOG_ERR,"GetShortPathName(%S) failed (%d)",w_argv0,
            GetLastError());
            free(w_short_argv0);
            w_short_argv0 = NULL;
        } else {
            syslog(LOG_DEBUG,"using short name %S for %S",w_short_argv0,
            w_argv0);
        }
    }
}

and then call CreateProcessW(w_short_argv0 ? w_short_argv0 : w_argv0...);

remembering to free(w_short_argv0); afterwards.

This may not solve every case, but it lets me spawn more child processes than I could before.