Fixes various warnings noticed on Windows (#425)

* Fixes various warnings noticed on Windows

- Adds a prototype for our implementation of vasprintf
- Return type of H5_get_utf16_str() is now non-const
- Fixes possible uninitialized return type in Wremove_utf8
- Better isolation of fork() code in accum.c:test_swmr_write_big()
- Better isolation of non-zlib code in dsets.c:test_filter_delete()
- Removed unused variable in trefer.c:test_reference_cmpnd_obj()

* Fixes clang-format issues

3 files changed, 18 insertions, 19 deletions

diff --git a/test/accum.c b/test/accum.c
index e9542cf..08fe926 100644
--- a/test/accum.c
+++ b/test/accum.c
@@ -2092,6 +2092,7 @@ error:
 unsigned
 test_swmr_write_big(hbool_t newest_format)
 {
+#if defined(H5_HAVE_FORK) && defined(H5_HAVE_WAITPID) && defined(H5_HAVE_UNISTD_H)
     hid_t    fid  = -1;   /* File ID */
     hid_t    fapl = -1;   /* File access property list */
     H5F_t *  rf   = NULL; /* File pointer */
@@ -2099,26 +2100,16 @@ test_swmr_write_big(hbool_t newest_format)
     uint8_t *wbuf2 = NULL, *rbuf = NULL; /* Buffers for reading & writing */
     uint8_t  wbuf[1024];                 /* Buffer for reading & writing */
     unsigned u;                          /* Local index variable */
-#ifdef H5_HAVE_UNISTD_H
-    pid_t pid;                      /* Process ID */
-#endif                              /* H5_HAVE_UNISTD_H */
-    int     status;                 /* Status returned from child process */
-    char *  driver         = NULL;  /* VFD string (from env variable) */
-    hbool_t api_ctx_pushed = FALSE; /* Whether API context pushed */
+    pid_t    pid;                        /* Process ID */
+    int      status;                     /* Status returned from child process */
+    char *   driver         = NULL;      /* VFD string (from env variable) */
+    hbool_t  api_ctx_pushed = FALSE;     /* Whether API context pushed */
 
     if (newest_format)
         TESTING("SWMR write of large metadata: with latest format")
     else
         TESTING("SWMR write of large metadata: with non-latest-format")
 
-#if !(defined(H5_HAVE_FORK) && defined(H5_HAVE_WAITPID))
-
-    SKIPPED();
-    HDputs("    Test skipped due to fork or waitpid not defined.");
-    return 0;
-
-#else /* defined(H5_HAVE_FORK && defined(H5_HAVE_WAITPID) */
-
     /* Skip this test if SWMR I/O is not supported for the VFD specified
      * by the environment variable.
      */
@@ -2296,7 +2287,11 @@ error:
 
     return 1;
 
-#endif
+#else
+    SKIPPED();
+    HDputs("    Test skipped due to fork, waitpid, or pid_t not defined.");
+    return 0;
+#endif /* defined(H5_HAVE_FORK) && defined(H5_HAVE_WAITPID) && defined(H5_HAVE_UNISTD_H) */
 
 } /* end test_swmr_write_big() */
 
diff --git a/test/dsets.c b/test/dsets.c
index 5dcdbce..8600d75 100644
--- a/test/dsets.c
+++ b/test/dsets.c
@@ -6976,6 +6976,7 @@ error:
 static herr_t
 test_filter_delete(hid_t file)
 {
+#ifdef H5_HAVE_FILTER_DEFLATE
     H5Z_filter_t filtn;                    /* filter identification number */
     hid_t        dsid          = -1;       /* dataset ID */
     hid_t        sid           = -1;       /* dataspace ID */
@@ -6987,6 +6988,7 @@ test_filter_delete(hid_t file)
     unsigned     flags;                    /* flags for filter */
     herr_t       ret;                      /* generic return value */
     int          i;
+#endif
 
     TESTING("filter deletion");
 
@@ -7088,9 +7090,7 @@ test_filter_delete(hid_t file)
         goto error;
 
     PASSED();
-#else
-    SKIPPED();
-#endif
+
     return SUCCEED;
 
 error:
@@ -7103,6 +7103,10 @@ error:
     }
     H5E_END_TRY;
     return FAIL;
+#else
+    SKIPPED();
+    return SUCCEED;
+#endif
 } /* end test_filter_delete() */
 
 /*-------------------------------------------------------------------------
diff --git a/test/trefer.c b/test/trefer.c
index 0d6ae75..6422a1b 100644
--- a/test/trefer.c
+++ b/test/trefer.c
@@ -832,7 +832,7 @@ test_reference_cmpnd_obj(void)
     hsize_t    cmpnd_dims[] = {1};
     hid_t      dapl_id; /* Dataset access property list     */
     unsigned * ibuf, *obuf;
-    unsigned   i, j;     /* Counters                         */
+    unsigned   i;        /* Counter                          */
     H5O_type_t obj_type; /* Object type                      */
     herr_t     ret;      /* Generic return value             */
     s2_t       cmpnd_wbuf, cmpnd_rbuf;