fix compiler warnings (#800)

* fix compiler warnings

* add free

Author: tgauth

contrib/win32/win32compat/fileio.c

@@ -702,7 +702,7 @@ fileio_write_wrapper(struct w32_io* pio, const void* buf, size_t bytes_to_copy)
 	int bytes_copied = -1;
 	size_t chunk_size = 0;
 
-	for (int i = 0; i < bytes_to_copy; i += WRITE_BUFFER_SIZE, chunk_count++) {
+	for (size_t i = 0; i < bytes_to_copy; i += WRITE_BUFFER_SIZE, chunk_count++) {
 		chunk_buf = (BYTE*)buf + chunk_count * WRITE_BUFFER_SIZE;
 		chunk_size = ((bytes_to_copy - i) >= WRITE_BUFFER_SIZE) ? WRITE_BUFFER_SIZE : (bytes_to_copy - i);
 		bytes_written = fileio_write(pio, chunk_buf, chunk_size);

contrib/win32/win32compat/misc.c

@@ -1262,7 +1262,7 @@ readpassphrase(const char *prompt, char *outBuf, size_t outBufLen, int flags)
 				fatal("character conversion failed");
 
 			/* append to output buffer if the characters fit */
-			if (current_index + utf8_read >= outBufLen - 1) break;
+			if (current_index + utf8_read >= (int)outBufLen - 1) break;
 			memcpy(&outBuf[current_index], utf8_char, utf8_read);
 			current_index += utf8_read;
 

contrib/win32/win32compat/w32fd.c

@@ -89,17 +89,19 @@ fd_table_initialize()
 {
 	struct w32_io *pio;
 	HANDLE wh;
-	char *stdio_mode_env;
+	char *stdio_mode_env = NULL;
 	int stdio_mode = NONSOCK_SYNC_FD;
+	size_t len = 0;
 
-	stdio_mode_env = getenv("OPENSSH_STDIO_MODE");
+	_dupenv_s(&stdio_mode_env, &len, "OPENSSH_STDIO_MODE");
 	if (stdio_mode_env != NULL) {
 		if (strcmp(stdio_mode_env, "sock") == 0)
 			stdio_mode = SOCK_FD;
 		else if (strcmp(stdio_mode_env, "nonsock") == 0)
 			stdio_mode = NONSOCK_FD;
 		else if (strcmp(stdio_mode_env, "nonsock_sync") == 0)
 			stdio_mode = NONSOCK_SYNC_FD;
+		free(stdio_mode_env);
 	}
 
 	/* table entries representing std in, out and error*/

contrib/win32/win32compat/win32_dirent.c

@@ -277,7 +277,7 @@ basename(char *path)
 	while (endp > path && (*endp == '/' || *endp == '\\'))
 		endp--;
 
-	int path_len = endp - path + 1;
+	size_t path_len = endp - path + 1;
 	if (strncpy_s(bname, PATH_MAX, path, path_len + 1)) {
 		return NULL;
 	}