update unions

Unions became tagged unions in snapsnot preview 2.

Refs: #59

Author: cjihrig

README.md

@@ -1702,13 +1702,13 @@ Members:
 
 - When `type` is [`UVWASI_EVENTTYPE_FD_READ`](#eventtype.fd_read) or [`UVWASI_EVENTTYPE_FD_WRITE`](#eventtype.fd_write):
 
-    - <a href="#event.u.fd_readwrite" name="event.u.fd_readwrite"></a>**`u.fd_readwrite`**
+    - <a href="#event.fd_readwrite" name="event.fd_readwrite"></a>**`fd_readwrite`**
 
-        - <a href="#event.u.fd_readwrite.nbytes" name="event.u.fd_readwrite.nbytes"></a><code>[\_\_wasi\_filesize\_t](#filesize) <strong>nbytes</strong></code>
+        - <a href="#event.fd_readwrite.nbytes" name="event.fd_readwrite.nbytes"></a><code>[\_\_wasi\_filesize\_t](#filesize) <strong>nbytes</strong></code>
 
             The number of bytes available for reading or writing.
 
-        - <a href="#event.u.fd_readwrite.flags" name="event.u.fd_readwrite.flags"></a><code>[\_\_wasi\_eventrwflags\_t](#eventrwflags) <strong>flags</strong></code>
+        - <a href="#event.fd_readwrite.flags" name="event.fd_readwrite.flags"></a><code>[\_\_wasi\_eventrwflags\_t](#eventrwflags) <strong>flags</strong></code>
 
             The state of the file descriptor.
 

include/wasi_types.h

@@ -169,7 +169,7 @@ typedef uint8_t uvwasi_preopentype_t;
 #define UVWASI_PREOPENTYPE_DIR 0
 
 typedef struct uvwasi_prestat_s {
-  uvwasi_preopentype_t pr_type;
+  uvwasi_preopentype_t tag;
   union uvwasi_prestat_u {
     struct uvwasi_prestat_dir_t {
       size_t pr_name_len;
@@ -236,20 +236,29 @@ typedef uint64_t uvwasi_timestamp_t;
 
 typedef uint64_t uvwasi_userdata_t;
 
+typedef union uvwasi_subscription_u_u_s {
+  struct {
+    uvwasi_clockid_t clock_id;
+    uvwasi_timestamp_t timeout;
+    uvwasi_timestamp_t precision;
+    uvwasi_subclockflags_t flags;
+  } clock;
+  struct {
+    uvwasi_fd_t fd;
+  } fd_read;
+  struct {
+    uvwasi_fd_t fd;
+  } fd_write;
+} uvwasi_subscription_u_u_t;
+
+typedef struct uvwasi_subscription_u_s {
+  uvwasi_eventtype_t tag;
+  uvwasi_subscription_u_u_t u;
+} uvwasi_subscription_u_t;
+
 typedef struct uvwasi_subscription_s {
   uvwasi_userdata_t userdata;
-  uvwasi_eventtype_t type;
-  union {
-    struct {
-      uvwasi_clockid_t clock_id;
-      uvwasi_timestamp_t timeout;
-      uvwasi_timestamp_t precision;
-      uvwasi_subclockflags_t flags;
-    } clock;
-    struct {
-      uvwasi_fd_t fd;
-    } fd_readwrite;
-  } u;
+  uvwasi_subscription_u_t u;
 } uvwasi_subscription_t;
 
 typedef struct uvwasi_dirent_s {
@@ -278,16 +287,16 @@ typedef struct uvwasi_filestat_s {
   uvwasi_timestamp_t st_ctim;
 } uvwasi_filestat_t;
 
+typedef struct uvwasi_event_fd_readwrite_s {
+  uvwasi_filesize_t nbytes;
+  uvwasi_eventrwflags_t flags;
+} uvwasi_event_fd_readwrite_t;
+
 typedef struct uvwasi_event_s {
   uvwasi_userdata_t userdata;
   uvwasi_errno_t error;
   uvwasi_eventtype_t type;
-  union {
-    struct {
-      uvwasi_filesize_t nbytes;
-      uvwasi_eventrwflags_t flags;
-    } fd_readwrite;
-  } u;
+  uvwasi_event_fd_readwrite_t fd_readwrite;
 } uvwasi_event_t;
 
 typedef uint8_t uvwasi_whence_t;

src/uvwasi.c

@@ -1263,7 +1263,7 @@ uvwasi_errno_t uvwasi_fd_prestat_get(uvwasi_t* uvwasi,
     goto exit;
   }
 
-  buf->pr_type = UVWASI_PREOPENTYPE_DIR;
+  buf->tag = UVWASI_PREOPENTYPE_DIR;
   buf->u.dir.pr_name_len = strlen(wrap->path) + 1;
   err = UVWASI_ESUCCESS;
 exit:

test/test-fd-prestat-dir-name.c

@@ -38,7 +38,7 @@ int main(void) {
   /* Verify uvwasi_fd_prestat_get(). */
   err = uvwasi_fd_prestat_get(&uvwasi, 3, &prestat);
   assert(err == 0);
-  assert(prestat.pr_type == UVWASI_PREOPENTYPE_DIR);
+  assert(prestat.tag == UVWASI_PREOPENTYPE_DIR);
   assert(prestat.u.dir.pr_name_len ==
          strlen(init_options.preopens[0].mapped_path) + 1);