compat/win32/headless.c

   1 /*
   2  * headless Git - run Git without opening a console window on Windows
   3  */
   4
   5 #define STRICT
   6 #define WIN32_LEAN_AND_MEAN
   7 #define UNICODE
   8 #define _UNICODE
   9 #include <windows.h>
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <wchar.h>
  13
  14 /*
  15  * If `dir` contains the path to a Git exec directory, extend `PATH` to
  16  * include the corresponding `bin/` directory (which is where all those
  17  * `.dll` files needed by `git.exe` are, on Windows).
  18  */
  19 static int extend_path(wchar_t *dir, size_t dir_len)
  20 {
  21         const wchar_t *suffix = L"\\libexec\\git-core";
  22         size_t suffix_len = wcslen(suffix);
  23         wchar_t *env;
  24         DWORD len;
  25
  26         if (dir_len < suffix_len)
  27                 return 0;
  28
  29         dir_len -= suffix_len;
  30         if (memcmp(dir + dir_len, suffix, suffix_len * sizeof(wchar_t)))
  31                 return 0;
  32
  33         len = GetEnvironmentVariableW(L"PATH", NULL, 0);
  34         if (!len)
  35                 return 0;
  36
  37         env = _alloca((dir_len + 5 + len) * sizeof(wchar_t));
  38         wcsncpy(env, dir, dir_len);
  39         wcscpy(env + dir_len, L"\\bin;");
  40         if (!GetEnvironmentVariableW(L"PATH", env + dir_len + 5, len))
  41                 return 0;
  42
  43         SetEnvironmentVariableW(L"PATH", env);
  44         return 1;
  45 }
  46
  47 int WINAPI wWinMain(_In_ HINSTANCE instance,
  48                     _In_opt_ HINSTANCE previous_instance,
  49                     _In_ LPWSTR command_line, _In_ int show)
  50 {
  51         wchar_t git_command_line[32768];
  52         size_t size = sizeof(git_command_line) / sizeof(wchar_t);
  53         const wchar_t *needs_quotes = L"";
  54         int slash = 0, i;
  55
  56         STARTUPINFO startup_info = {
  57                 .cb = sizeof(STARTUPINFO),
  58                 .dwFlags = STARTF_USESHOWWINDOW,
  59                 .wShowWindow = SW_HIDE,
  60         };
  61         PROCESS_INFORMATION process_info = { 0 };
  62         DWORD creation_flags = CREATE_UNICODE_ENVIRONMENT |
  63                 CREATE_NEW_CONSOLE | CREATE_NO_WINDOW;
  64         DWORD exit_code;
  65
  66         /* First, determine the full path of argv[0] */
  67         for (i = 0; _wpgmptr[i]; i++)
  68                 if (_wpgmptr[i] == L' ')
  69                         needs_quotes = L"\"";
  70                 else if (_wpgmptr[i] == L'\\')
  71                         slash = i;
  72
  73         if (slash >= size - 11)
  74                 return 127; /* Too long path */
  75
  76         /* If it is in Git's exec path, add the bin/ directory to the PATH */
  77         extend_path(_wpgmptr, slash);
  78
  79         /* Then, add the full path of `git.exe` as argv[0] */
  80         i = swprintf_s(git_command_line, size, L"%ls%.*ls\\git.exe%ls",
  81                        needs_quotes, slash, _wpgmptr, needs_quotes);
  82         if (i < 0)
  83                 return 127; /* Too long path */
  84
  85         if (*command_line) {
  86                 /* Now, append the command-line arguments */
  87                 i = swprintf_s(git_command_line + i, size - i,
  88                                L" %ls", command_line);
  89                 if (i < 0)
  90                         return 127;
  91         }
  92
  93         startup_info.hStdInput = GetStdHandle(STD_INPUT_HANDLE);
  94         startup_info.hStdOutput = GetStdHandle(STD_OUTPUT_HANDLE);
  95         startup_info.hStdError = GetStdHandle(STD_ERROR_HANDLE);
  96
  97         if (!CreateProcess(NULL, /* infer argv[0] from the command line */
  98                            git_command_line, /* modified command line */
  99                            NULL, /* inherit process handles? */
 100                            NULL, /* inherit thread handles? */
 101                            FALSE, /* handles inheritable? */
 102                            creation_flags,
 103                            NULL, /* use this process' environment */
 104                            NULL, /* use this process' working directory */
 105                            &startup_info, &process_info))
 106                 return 129; /* could not start */
 107         WaitForSingleObject(process_info.hProcess, INFINITE);
 108         if (!GetExitCodeProcess(process_info.hProcess, &exit_code))
 109                 exit_code = 130; /* Could not determine exit code? */
 110
 111         CloseHandle(process_info.hProcess);
 112         CloseHandle(process_info.hThread);
 113
 114         return (int)exit_code;
 115 }