msvc: provide a main() wrapper similar to mingw_main()

The MINGW version of the main() wrapper gets away with declaring symbols
that were intentionally not exported. However, some of these symbols do
not actually exist in MSVC's UCRT.

So let's add an MSVC version of the main() wrapper that uses wmain() and
imports the UNICODE argv and environment. While at it, we pass our UTF-8
version of ARGV to the real main -- rather than overwriting __argv as is
done in the MINGW Version.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>

compat/mingw.c

@@ -2993,6 +2993,7 @@ int handle_long_path(wchar_t *path, int len, int max_path, int expand)
 	}
 }
 
+#if !defined(_MSC_VER)
 /*
  * Disable MSVCRT command line wildcard expansion (__getmainargs called from
  * mingw startup code, see init.c in mingw runtime).
@@ -3005,6 +3006,7 @@ typedef struct {
 
 extern int __wgetmainargs(int *argc, wchar_t ***argv, wchar_t ***env, int glob,
 		_startupinfo *si);
+#endif
 
 static NORETURN void die_startup(void)
 {
@@ -3082,6 +3084,95 @@ static void maybe_redirect_std_handles(void)
 				  GENERIC_WRITE, FILE_FLAG_NO_BUFFERING);
 }
 
+#if defined(_MSC_VER)
+
+/*
+ * This routine sits between wmain() and "main" in git.exe.
+ * We receive UNICODE (wchar_t) values for argv and env.
+ *
+ * To be more compatible with the core git code, we convert
+ * argv into UTF8 and pass them directly to the "main" routine.
+ *
+ * We don't bother converting the given UNICODE env vector,
+ * but rather leave them in the CRT.  We replaced the various
+ * getenv/putenv routines to pull them directly from the CRT.
+ *
+ * This is unlike the MINGW version:
+ * [] It does the UNICODE-2-UTF8 conversion on both sets and
+ *    stuffs the values back into the CRT using exported symbols.
+ * [] It also maintains a private copy of the environment and
+ *    tries to track external changes to it.
+ */
+int msc_startup(int argc, wchar_t **w_argv, wchar_t **w_env)
+{
+	char **my_utf8_argv = NULL, **save = NULL;
+	char *buffer = NULL;
+	int maxlen;
+	int k, exit_status;
+
+#ifdef USE_MSVC_CRTDBG
+	_CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);
+#endif
+
+	maybe_redirect_std_handles();
+
+	/* determine size of argv conversion buffer */
+	maxlen = wcslen(_wpgmptr);
+	for (k = 1; k < argc; k++)
+		maxlen = max(maxlen, wcslen(w_argv[k]));
+
+	/* allocate buffer (wchar_t encodes to max 3 UTF-8 bytes) */
+	maxlen = 3 * maxlen + 1;
+	buffer = malloc_startup(maxlen);
+
+	/*
+	 * Create a UTF-8 version of w_argv. Also create a "save" copy
+	 * to remember all the string pointers because parse_options()
+	 * will remove claimed items from the argv that we pass down.
+	 */
+	ALLOC_ARRAY(my_utf8_argv, argc + 1);
+	ALLOC_ARRAY(save, argc + 1);
+	save[0] = my_utf8_argv[0] = wcstoutfdup_startup(buffer, _wpgmptr, maxlen);
+	for (k = 1; k < argc; k++)
+		save[k] = my_utf8_argv[k] = wcstoutfdup_startup(buffer, w_argv[k], maxlen);
+	save[k] = my_utf8_argv[k] = NULL;
+
+	free(buffer);
+
+	/* fix Windows specific environment settings */
+	setup_windows_environment();
+
+	unset_environment_variables = xstrdup("PERL5LIB");
+
+	/* initialize critical section for waitpid pinfo_t list */
+	InitializeCriticalSection(&pinfo_cs);
+	InitializeCriticalSection(&phantom_symlinks_cs);
+
+	/* set up default file mode and file modes for stdin/out/err */
+	_fmode = _O_BINARY;
+	_setmode(_fileno(stdin), _O_BINARY);
+	_setmode(_fileno(stdout), _O_BINARY);
+	_setmode(_fileno(stderr), _O_BINARY);
+
+	/* initialize Unicode console */
+	winansi_init();
+
+	/* init length of current directory for handle_long_path */
+	current_directory_len = GetCurrentDirectoryW(0, NULL);
+
+	/* invoke the real main() using our utf8 version of argv. */
+	exit_status = msc_main(argc, my_utf8_argv);
+
+	for (k = 0; k < argc; k++)
+		free(save[k]);
+	free(save);
+	free(my_utf8_argv);
+
+	return exit_status;
+}
+
+#else
+
 void mingw_startup(void)
 {
 	int i, maxlen, argc;
@@ -3160,6 +3251,8 @@ void mingw_startup(void)
 	current_directory_len = GetCurrentDirectoryW(0, NULL);
 }
 
+#endif
+
 int uname(struct utsname *buf)
 {
 	unsigned v = (unsigned)GetVersion();

compat/mingw.h

@@ -693,7 +693,26 @@ extern CRITICAL_SECTION pinfo_cs;
 
 /*
  * A replacement of main() that adds win32 specific initialization.
+ *
+ * Note that the end of these macros are unterminated so that the
+ * brace group following the use of the macro is the body of the
+ * function.
  */
+#if defined(_MSC_VER)
+
+int msc_startup(int argc, wchar_t **w_argv, wchar_t **w_env);
+extern int msc_main(int argc, const char **argv);
+
+#define main(c,v) dummy_decl_msc_main(void);				\
+int wmain(int my_argc,									\
+		  wchar_t **my_w_argv,							\
+		  wchar_t **my_w_env)							\
+{														\
+	return msc_startup(my_argc, my_w_argv, my_w_env);	\
+}														\
+int msc_main(c, v)
+
+#else
 
 void mingw_startup(void);
 #define main(c,v) dummy_decl_mingw_main(void); \
@@ -705,6 +724,8 @@ int main(int argc, const char **argv) \
 } \
 static int mingw_main(c,v)
 
+#endif
+
 /*
  * Used by Pthread API implementation for Windows
  */