Display how arguments are parsed in Windows

getargs.c

/*
Display how arguments are parsed in Windows.

VS 2010 x86:
cl /nologo /W4 getargs.c /MD /Fegetargs-cl && getargs-cl

VS 2010 x86, for win2k compatibility build against the WinDDK:
cl /nologo /W4 getargs.c /MD /Fegetargs-cl C:\WinDDK\7600.16385.1\lib\win7\i386\msvcrt_win2000.obj /IC:\WinDDK\7600.16385.1\inc\crt /link /SUBSYSTEM:CONSOLE,5.00 /OSVERSION:5.00 /LIBPATH:C:\WinDDK\7600.16385.1\lib\Crt\i386 && getargs-cl

mingw x86:
gcc -Wall -o getargs-gcc getargs.c -lpsapi && getargs-gcc

Copyright (C) 2016 Jay Satiro <raysatiro@yahoo.com>
http://curl.haxx.se/docs/copyright.html

https://curl.haxx.se/mail/archive-2016-12/0049.html

https://gist.github.com/jay/19aba48653bd591cf4b90eb9249a302c
*/

/*
Dev notes:

To print wide character strings (which are converted by the CRT to ANSI) use
[f]wprintf %s instead of printf %S because the latter will stop printing the
format string if conversion of the wide character string fails.

Additionally it seems gcc/MinGW builds cannot handle unicode characters at the
command line, therefore something like (UTF-8 encoded) getargs-gcc спасти
causes the parser to erroneously create argv that are actually directory names.
*/

#ifdef _MSC_VER
#pragma warning(disable: 4996) /* deprecated functions */
#pragma comment(lib, "psapi.lib")
#endif

#define _CRT_SECURE_NO_WARNINGS
#define _WIN32_WINNT 0x0500
#define PSAPI_VERSION 1

#include <stdio.h>
#include <stdlib.h>

#include <windows.h>
#include <psapi.h>
#include <tlhelp32.h>

#ifndef PROCESS_QUERY_LIMITED_INFORMATION
#define PROCESS_QUERY_LIMITED_INFORMATION 0x1000
#endif

OSVERSIONINFO ver = { sizeof ver, };
DWORD (WINAPI *pGetProcessImageFileNameA)(HANDLE, LPSTR, DWORD) = NULL;

DWORD GetParentProcessId();
char *GetProcessPathname(DWORD);

int main(int argc, char **argv)
{
  int i;
  DWORD parent_pid;
  wchar_t path[32767];
  HMODULE psapi;

  printf("\n");

  if(!GetVersionEx(&ver)) {
    fprintf(stderr, "FATAL: GetVersionEx failed, gle: %I32u\n",
            GetLastError());
    exit(1);
  }

  psapi = LoadLibraryA("psapi");
  if(psapi) {
    pGetProcessImageFileNameA = (DWORD (WINAPI *)(HANDLE, LPSTR, DWORD))
      GetProcAddress(psapi, "GetProcessImageFileNameA");
  }

  if(GetEnvironmentVariableW(L"PATH", path, sizeof path) < sizeof path) {
    wprintf(L"PATH=%s\n\n", path);
  }
  else {
    fprintf(stderr, "ERROR: GetEnvironmentVariableW failed, gle: %I32u\n",
            GetLastError());
  }

  parent_pid = GetParentProcessId();

  if(parent_pid) {
    char *parent_path = GetProcessPathname(parent_pid);

    printf("Parent id: %I32u\n", parent_pid);
    printf("Parent path: %s\n\n", parent_path ? parent_path : "");
  }
  else {
    fprintf(stderr, "ERROR: GetParentProcessId failed!\n");
  }

  // If conversion fails it shows ?????? in cl builds and nothing in gcc builds
  wprintf(L"GetCommandLineW: %s\n\n", GetCommandLineW());

  for(i = 0; i < argc; ++i) {
    printf("argv[%d]: %s\n", i, argv[i]);
  }

  return 1;
}

DWORD GetParentProcessId()
{
  BOOL b;
  DWORD our_pid = GetCurrentProcessId();
  PROCESSENTRY32 pe = { sizeof pe, };
  HANDLE snapshot;
  static DWORD parent_pid;

  if(parent_pid)
    return parent_pid;

  snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);

  if(snapshot == INVALID_HANDLE_VALUE) {
    fprintf(stderr, "ERROR: CreateToolhelp32Snapshot failed creating process "
                    "list, gle: %I32u\n",
            GetLastError());
    return parent_pid;
  }

  for(b = Process32First(snapshot, &pe); b; b = Process32Next(snapshot, &pe)) {
    if(our_pid == pe.th32ProcessID) {
      parent_pid = pe.th32ParentProcessID;
      break;
    }
  }

  if(!parent_pid)
    fprintf(stderr, "ERROR: Parent pid not found in process list!\n");

  CloseHandle(snapshot);
  return parent_pid;
}

// Returns pathname of a process or NULL on error
// pathname is freed by caller
char *GetProcessPathname(DWORD process_id)
{
  int i;
  HANDLE process;
  DWORD drives;
  char *path, buf[32768], buf2[32768];

  process = OpenProcess((!pGetProcessImageFileNameA ?
                         (PROCESS_QUERY_INFORMATION | PROCESS_VM_READ):
                         ((ver.dwMajorVersion <= 5) ?
                          PROCESS_QUERY_INFORMATION :
                          PROCESS_QUERY_LIMITED_INFORMATION)),
                        FALSE, process_id);

  if(!process) {
    fprintf(stderr, "ERROR: OpenProcess failed opening process id "
                    "%I32u, gle: %I32u\n",
            process_id, GetLastError());
    return NULL;
  }

  if(pGetProcessImageFileNameA) {
    if(!pGetProcessImageFileNameA(process, buf, sizeof buf)) {
      fprintf(stderr, "ERROR: GetProcessImageFileName failed getting the path "
                      "of process id %I32u, gle: %I32u\n",
              process_id, GetLastError());
      return NULL;
    }

    drives = GetLogicalDrives();
    if(!drives) {
      fprintf(stderr, "ERROR: GetLogicalDrives failed, gle: %I32u\n",
              GetLastError());
      return NULL;
    }

    for(i = 0; i < 26; ++i) {
      size_t rootlen;
      char dev[] = "A:";

      if(!(drives & (1 << i)))
        continue;

      dev[0] += (char)i;

      if(!QueryDosDeviceA(dev, buf2, sizeof buf2) || !buf2[0])
        continue;

      rootlen = strlen(buf2);
      if(buf2[rootlen - 1] != '\\') {
        if(rootlen + 1 == sizeof buf2)
          continue;
        buf2[rootlen] = '\\';
        ++rootlen;
        buf2[rootlen] = 0;
      }

      if(!strncmp(buf, buf2, rootlen)) {
        size_t buflen = strlen(buf);
        size_t devlen = strlen(dev);
        if(buflen - rootlen + devlen + 1 /* \ */ + 1 > sizeof buf)
          continue;
        memmove(&buf[devlen + 1], &buf[rootlen], buflen - rootlen + 1);
        strcpy(buf, dev);
        buf[devlen] = '\\';
        break;
      }
    }
  }
  /* GetProcessImageFileNameA is not in Win2k so use GetModuleFileNameExA */
  else {
    if(ver.dwMajorVersion > 5 ||
       (ver.dwMajorVersion == 5 && ver.dwMinorVersion > 0)) {
      fprintf(stderr, "ERROR: GetProcessImageFileNameA not found, falling "
                      "back on GetModuleFileNameExA\n");
    }
    if(!GetModuleFileNameExA(process, NULL, buf, sizeof buf)) {
      fprintf(stderr, "ERROR: GetModuleFileNameExA failed getting the path "
                      "of process id %I32u, gle: %I32u\n",
              process_id, GetLastError());
      return NULL;
    }
  }

  path = malloc(strlen(buf) + 1);
  if(!path) {
    fprintf(stderr, "ERROR: malloc out of memory\n");
    return NULL;
  }

  strcpy(path, buf);
  return path;
}