Fixed uninitialized warnings (#360)

* Fixed all -Wsometimes-uninitialized warnings by initializing variables

* Fixed all -Wconditional-uninitialized warnings by initializing variables

* Commit alignment changes from running bin/format_source with clang
version 10.0.1.

Co-authored-by: Larry Knox <lrknox@hdfgroup.org>

30 files changed, 156 insertions, 155 deletions

diff --git a/src/H5B2int.c b/src/H5B2int.c
index ef90bbf..610da6c 100644
--- a/src/H5B2int.c
+++ b/src/H5B2int.c
@@ -138,15 +138,15 @@ H5B2__split1(H5B2_hdr_t *hdr, uint16_t depth, H5B2_node_ptr_t *curr_node_ptr,
              unsigned *parent_cache_info_flags_ptr, H5B2_internal_t *internal, unsigned *internal_flags_ptr,
              unsigned idx)
 {
-    const H5AC_class_t *child_class;                            /* Pointer to child node's class info */
-    haddr_t             left_addr, right_addr;                  /* Addresses of left & right child nodes */
-    void *              left_child = NULL, *right_child = NULL; /* Pointers to child nodes */
-    uint16_t *          left_nrec, *right_nrec;                 /* Pointers to child # of records */
-    uint8_t *           left_native, *right_native;             /* Pointers to childs' native records */
-    H5B2_node_ptr_t *   left_node_ptrs = NULL,
-                    *right_node_ptrs   = NULL; /* Pointers to childs' node pointer info */
-    uint16_t mid_record;                       /* Index of "middle" record in current node */
-    uint16_t old_node_nrec;                    /* Number of records in internal node split */
+    const H5AC_class_t *child_class;                             /* Pointer to child node's class info */
+    haddr_t   left_addr = HADDR_UNDEF, right_addr = HADDR_UNDEF; /* Addresses of left & right child nodes */
+    void *    left_child = NULL, *right_child = NULL;            /* Pointers to child nodes */
+    uint16_t *left_nrec, *right_nrec;                            /* Pointers to child # of records */
+    uint8_t * left_native, *right_native;                        /* Pointers to childs' native records */
+    H5B2_node_ptr_t *left_node_ptrs  = NULL,
+                    *right_node_ptrs = NULL; /* Pointers to childs' node pointer info */
+    uint16_t mid_record;                     /* Index of "middle" record in current node */
+    uint16_t old_node_nrec;                  /* Number of records in internal node split */
     unsigned left_child_flags  = H5AC__NO_FLAGS_SET,
              right_child_flags = H5AC__NO_FLAGS_SET; /* Flags for unprotecting child nodes */
     herr_t ret_value           = SUCCEED;            /* Return value */
@@ -423,13 +423,13 @@ done:
 herr_t
 H5B2__redistribute2(H5B2_hdr_t *hdr, uint16_t depth, H5B2_internal_t *internal, unsigned idx)
 {
-    const H5AC_class_t *child_class;                            /* Pointer to child node's class info */
-    haddr_t             left_addr, right_addr;                  /* Addresses of left & right child nodes */
-    void *              left_child = NULL, *right_child = NULL; /* Pointers to child nodes */
-    uint16_t *          left_nrec, *right_nrec;                 /* Pointers to child # of records */
-    uint8_t *           left_native, *right_native;             /* Pointers to childs' native records */
-    H5B2_node_ptr_t *   left_node_ptrs = NULL,
-                    *right_node_ptrs   = NULL;          /* Pointers to childs' node pointer info */
+    const H5AC_class_t *child_class;                             /* Pointer to child node's class info */
+    haddr_t   left_addr = HADDR_UNDEF, right_addr = HADDR_UNDEF; /* Addresses of left & right child nodes */
+    void *    left_child = NULL, *right_child = NULL;            /* Pointers to child nodes */
+    uint16_t *left_nrec, *right_nrec;                            /* Pointers to child # of records */
+    uint8_t * left_native, *right_native;                        /* Pointers to childs' native records */
+    H5B2_node_ptr_t *left_node_ptrs  = NULL,
+                    *right_node_ptrs = NULL;            /* Pointers to childs' node pointer info */
     hssize_t left_moved_nrec = 0, right_moved_nrec = 0; /* Number of records moved, for internal redistrib */
     unsigned left_child_flags  = H5AC__NO_FLAGS_SET,
              right_child_flags = H5AC__NO_FLAGS_SET; /* Flags for unprotecting child nodes */
@@ -696,20 +696,20 @@ H5B2__redistribute3(H5B2_hdr_t *hdr, uint16_t depth, H5B2_internal_t *internal,
                     unsigned idx)
 {
     H5B2_node_ptr_t *left_node_ptrs      = NULL,
-                    *right_node_ptrs     = NULL;                /* Pointers to childs' node pointer info */
-    H5B2_node_ptr_t *   middle_node_ptrs = NULL;                /* Pointers to childs' node pointer info */
-    const H5AC_class_t *child_class;                            /* Pointer to child node's class info */
-    haddr_t             left_addr, right_addr;                  /* Addresses of left & right child nodes */
-    haddr_t             middle_addr;                            /* Address of middle child node */
-    void *              left_child = NULL, *right_child = NULL; /* Pointers to child nodes */
-    void *              middle_child = NULL;                    /* Pointers to middle child node */
-    uint16_t *          left_nrec, *right_nrec;                 /* Pointers to child # of records */
-    uint16_t *          middle_nrec;                            /* Pointers to middle child # of records */
-    uint8_t *           left_native, *right_native;             /* Pointers to childs' native records */
-    uint8_t *           middle_native;                  /* Pointers to middle child's native records */
-    hssize_t left_moved_nrec = 0, right_moved_nrec = 0; /* Number of records moved, for internal split */
-    hssize_t middle_moved_nrec  = 0;                    /* Number of records moved, for internal split */
-    unsigned left_child_flags   = H5AC__NO_FLAGS_SET,
+                    *right_node_ptrs     = NULL;                 /* Pointers to childs' node pointer info */
+    H5B2_node_ptr_t *   middle_node_ptrs = NULL;                 /* Pointers to childs' node pointer info */
+    const H5AC_class_t *child_class;                             /* Pointer to child node's class info */
+    haddr_t   left_addr = HADDR_UNDEF, right_addr = HADDR_UNDEF; /* Addresses of left & right child nodes */
+    haddr_t   middle_addr = HADDR_UNDEF;                         /* Address of middle child node */
+    void *    left_child = NULL, *right_child = NULL;            /* Pointers to child nodes */
+    void *    middle_child = NULL;                               /* Pointers to middle child node */
+    uint16_t *left_nrec, *right_nrec;                            /* Pointers to child # of records */
+    uint16_t *middle_nrec;                                       /* Pointers to middle child # of records */
+    uint8_t * left_native, *right_native;                        /* Pointers to childs' native records */
+    uint8_t * middle_native;                             /* Pointers to middle child's native records */
+    hssize_t  left_moved_nrec = 0, right_moved_nrec = 0; /* Number of records moved, for internal split */
+    hssize_t  middle_moved_nrec = 0;                     /* Number of records moved, for internal split */
+    unsigned  left_child_flags  = H5AC__NO_FLAGS_SET,
              right_child_flags  = H5AC__NO_FLAGS_SET; /* Flags for unprotecting child nodes */
     unsigned middle_child_flags = H5AC__NO_FLAGS_SET; /* Flags for unprotecting child nodes */
     herr_t   ret_value          = SUCCEED;            /* Return value */
@@ -1122,16 +1122,16 @@ H5B2__merge2(H5B2_hdr_t *hdr, uint16_t depth, H5B2_node_ptr_t *curr_node_ptr,
              unsigned *parent_cache_info_flags_ptr, H5B2_internal_t *internal, unsigned *internal_flags_ptr,
              unsigned idx)
 {
-    const H5AC_class_t *child_class;                            /* Pointer to child node's class info */
-    haddr_t             left_addr, right_addr;                  /* Addresses of left & right child nodes */
-    void *              left_child = NULL, *right_child = NULL; /* Pointers to left & right child nodes */
-    uint16_t *          left_nrec, *right_nrec;     /* Pointers to left & right child # of records */
-    uint8_t *           left_native, *right_native; /* Pointers to left & right children's native records */
-    H5B2_node_ptr_t *   left_node_ptrs = NULL,
-                    *right_node_ptrs   = NULL; /* Pointers to childs' node pointer info */
-    unsigned left_child_flags          = H5AC__NO_FLAGS_SET,
-             right_child_flags         = H5AC__NO_FLAGS_SET; /* Flags for unprotecting child nodes */
-    herr_t ret_value                   = SUCCEED;            /* Return value */
+    const H5AC_class_t *child_class;                             /* Pointer to child node's class info */
+    haddr_t   left_addr = HADDR_UNDEF, right_addr = HADDR_UNDEF; /* Addresses of left & right child nodes */
+    void *    left_child = NULL, *right_child = NULL;            /* Pointers to left & right child nodes */
+    uint16_t *left_nrec, *right_nrec;     /* Pointers to left & right child # of records */
+    uint8_t * left_native, *right_native; /* Pointers to left & right children's native records */
+    H5B2_node_ptr_t *left_node_ptrs  = NULL,
+                    *right_node_ptrs = NULL; /* Pointers to childs' node pointer info */
+    unsigned left_child_flags        = H5AC__NO_FLAGS_SET,
+             right_child_flags       = H5AC__NO_FLAGS_SET; /* Flags for unprotecting child nodes */
+    herr_t ret_value                 = SUCCEED;            /* Return value */
 
     FUNC_ENTER_PACKAGE
 
@@ -1297,19 +1297,19 @@ H5B2__merge3(H5B2_hdr_t *hdr, uint16_t depth, H5B2_node_ptr_t *curr_node_ptr,
              unsigned *parent_cache_info_flags_ptr, H5B2_internal_t *internal, unsigned *internal_flags_ptr,
              unsigned idx)
 {
-    const H5AC_class_t *child_class;                            /* Pointer to child node's class info */
-    haddr_t             left_addr, right_addr;                  /* Addresses of left & right child nodes */
-    haddr_t             middle_addr;                            /* Address of middle child node */
-    void *              left_child = NULL, *right_child = NULL; /* Pointers to left & right child nodes */
-    void *              middle_child = NULL;                    /* Pointer to middle child node */
-    uint16_t *          left_nrec, *right_nrec;     /* Pointers to left & right child # of records */
-    uint16_t *          middle_nrec;                /* Pointer to middle child # of records */
-    uint8_t *           left_native, *right_native; /* Pointers to left & right children's native records */
-    uint8_t *           middle_native;              /* Pointer to middle child's native records */
-    H5B2_node_ptr_t *   left_node_ptrs = NULL,
-                    *right_node_ptrs   = NULL; /* Pointers to childs' node pointer info */
-    H5B2_node_ptr_t *middle_node_ptrs  = NULL; /* Pointer to child's node pointer info */
-    hsize_t          middle_moved_nrec;        /* Number of records moved, for internal split */
+    const H5AC_class_t *child_class;                             /* Pointer to child node's class info */
+    haddr_t   left_addr = HADDR_UNDEF, right_addr = HADDR_UNDEF; /* Addresses of left & right child nodes */
+    haddr_t   middle_addr = HADDR_UNDEF;                         /* Address of middle child node */
+    void *    left_child = NULL, *right_child = NULL;            /* Pointers to left & right child nodes */
+    void *    middle_child = NULL;                               /* Pointer to middle child node */
+    uint16_t *left_nrec, *right_nrec;     /* Pointers to left & right child # of records */
+    uint16_t *middle_nrec;                /* Pointer to middle child # of records */
+    uint8_t * left_native, *right_native; /* Pointers to left & right children's native records */
+    uint8_t * middle_native;              /* Pointer to middle child's native records */
+    H5B2_node_ptr_t *left_node_ptrs   = NULL,
+                    *right_node_ptrs  = NULL; /* Pointers to childs' node pointer info */
+    H5B2_node_ptr_t *middle_node_ptrs = NULL; /* Pointer to child's node pointer info */
+    hsize_t          middle_moved_nrec;       /* Number of records moved, for internal split */
     unsigned         left_child_flags = H5AC__NO_FLAGS_SET,
              right_child_flags        = H5AC__NO_FLAGS_SET; /* Flags for unprotecting child nodes */
     unsigned middle_child_flags       = H5AC__NO_FLAGS_SET; /* Flags for unprotecting child nodes */
@@ -1933,7 +1933,7 @@ H5B2__update_flush_depend(H5B2_hdr_t *hdr, unsigned depth, const H5B2_node_ptr_t
 
     /* If the node is in the cache, check for retargeting its parent */
     if (node_status & H5AC_ES__IN_CACHE) {
-        void ** parent_ptr;          /* Pointer to child node's parent */
+        void ** parent_ptr  = NULL;  /* Pointer to child node's parent */
         hbool_t update_deps = FALSE; /* Whether to update flush dependencies */
 
         /* Get child node pointer */
diff --git a/src/H5B2leaf.c b/src/H5B2leaf.c
index 199e011..20ace84 100644
--- a/src/H5B2leaf.c
+++ b/src/H5B2leaf.c
@@ -607,11 +607,11 @@ herr_t
 H5B2__swap_leaf(H5B2_hdr_t *hdr, uint16_t depth, H5B2_internal_t *internal, unsigned *internal_flags_ptr,
                 unsigned idx, void *swap_loc)
 {
-    const H5AC_class_t *child_class;         /* Pointer to child node's class info */
-    haddr_t             child_addr;          /* Address of child node */
-    void *              child = NULL;        /* Pointer to child node */
-    uint8_t *           child_native;        /* Pointer to child's native records */
-    herr_t              ret_value = SUCCEED; /* Return value */
+    const H5AC_class_t *child_class;              /* Pointer to child node's class info */
+    haddr_t             child_addr = HADDR_UNDEF; /* Address of child node */
+    void *              child      = NULL;        /* Pointer to child node */
+    uint8_t *           child_native;             /* Pointer to child's native records */
+    herr_t              ret_value = SUCCEED;      /* Return value */
 
     FUNC_ENTER_PACKAGE
 
diff --git a/src/H5C.c b/src/H5C.c
index 47a06d6..9369506 100644
--- a/src/H5C.c
+++ b/src/H5C.c
@@ -2229,8 +2229,8 @@ H5C_protect(H5F_t *f, const H5C_class_t *type, haddr_t addr, void *udata, unsign
 #ifdef H5_HAVE_PARALLEL
     hbool_t coll_access = FALSE; /* whether access to the cache entry is done collectively */
 #endif                           /* H5_HAVE_PARALLEL */
-    hbool_t            write_permitted;
-    hbool_t            was_loaded = FALSE; /* Whether the entry was loaded as a result of the protect */
+    hbool_t            write_permitted = FALSE;
+    hbool_t            was_loaded      = FALSE; /* Whether the entry was loaded as a result of the protect */
     size_t             empty_space;
     void *             thing;
     H5C_cache_entry_t *entry_ptr;
diff --git a/src/H5Dchunk.c b/src/H5Dchunk.c
index f711383..bd3b1ed 100644
--- a/src/H5Dchunk.c
+++ b/src/H5Dchunk.c
@@ -3151,9 +3151,9 @@ H5D__chunk_hash_val(const H5D_shared_t *shared, const hsize_t *scaled)
 herr_t
 H5D__chunk_lookup(const H5D_t *dset, const hsize_t *scaled, H5D_chunk_ud_t *udata)
 {
-    H5D_rdcc_ent_t *     ent = NULL; /* Cache entry */
-    H5O_storage_chunk_t *sc  = &(dset->shared->layout.storage.u.chunk);
-    unsigned             idx;                 /* Index of chunk in cache, if present */
+    H5D_rdcc_ent_t *     ent       = NULL; /* Cache entry */
+    H5O_storage_chunk_t *sc        = &(dset->shared->layout.storage.u.chunk);
+    unsigned             idx       = 0;       /* Index of chunk in cache, if present */
     hbool_t              found     = FALSE;   /* In cache? */
     herr_t               ret_value = SUCCEED; /* Return value */
 
diff --git a/src/H5Dvirtual.c b/src/H5Dvirtual.c
index 0faa1ca..ea38e0a 100644
--- a/src/H5Dvirtual.c
+++ b/src/H5Dvirtual.c
@@ -2299,7 +2299,7 @@ done:
 hbool_t
 H5D__virtual_is_space_alloc(const H5O_storage_t H5_ATTR_UNUSED *storage)
 {
-    hbool_t ret_value; /* Return value */
+    hbool_t ret_value = FALSE; /* Return value */
 
     FUNC_ENTER_PACKAGE_NOERR
 
@@ -2383,7 +2383,7 @@ H5D__virtual_pre_io(H5D_io_info_t *io_info, H5O_storage_virtual_t *storage, cons
     hssize_t select_nelmts;              /* Number of elements in selection */
     hsize_t  bounds_start[H5S_MAX_RANK]; /* Selection bounds start */
     hsize_t  bounds_end[H5S_MAX_RANK];   /* Selection bounds end */
-    int      rank;
+    int      rank        = 0;
     hbool_t  bounds_init = FALSE; /* Whether bounds_start, bounds_end, and rank are valid */
     size_t   i, j, k;             /* Local index variables */
     herr_t   ret_value = SUCCEED; /* Return value */
diff --git a/src/H5EA.c b/src/H5EA.c
index 2c47925..4d6b7c1 100644
--- a/src/H5EA.c
+++ b/src/H5EA.c
@@ -722,7 +722,8 @@ BEGIN_FUNC(PRIV, ERR, herr_t, SUCCEED, FAIL, H5EA_get(const H5EA_t *ea, hsize_t
     /* Local variables */
     H5EA_hdr_t *hdr = ea->hdr; /* Header for EA */
     void *thing = NULL; /* Pointer to the array metadata containing the array index we are interested in */
-    H5EA__unprotect_func_t thing_unprot_func; /* Function pointer for unprotecting the array metadata */
+    H5EA__unprotect_func_t thing_unprot_func =
+        NULL; /* Function pointer for unprotecting the array metadata */
 
     /*
      * Check arguments.
diff --git a/src/H5FDlog.c b/src/H5FDlog.c
index 8a1d805..aa2d6db 100644
--- a/src/H5FDlog.c
+++ b/src/H5FDlog.c
@@ -484,8 +484,8 @@ H5FD__log_open(const char *name, unsigned flags, hid_t fapl_id, haddr_t maxaddr)
 #ifdef H5_HAVE_WIN32_API
     struct _BY_HANDLE_FILE_INFORMATION fileinfo;
 #endif
-    H5_timer_t open_timer; /* Timer for open() call */
-    H5_timer_t stat_timer; /* Timer for stat() call */
+    H5_timer_t open_timer = {{0}, {0}, {0}, FALSE}; /* Timer for open() call */
+    H5_timer_t stat_timer = {{0}, {0}, {0}, FALSE}; /* Timer for stat() call */
     h5_stat_t  sb;
     H5FD_t *   ret_value = NULL; /* Return value */
 
@@ -677,9 +677,9 @@ done:
 static herr_t
 H5FD__log_close(H5FD_t *_file)
 {
-    H5FD_log_t *file = (H5FD_log_t *)_file;
-    H5_timer_t  close_timer;         /* Timer for close() call */
-    herr_t      ret_value = SUCCEED; /* Return value */
+    H5FD_log_t *file        = (H5FD_log_t *)_file;
+    H5_timer_t  close_timer = {{0}, {0}, {0}, FALSE}; /* Timer for close() call */
+    herr_t      ret_value   = SUCCEED;                /* Return value */
 
     FUNC_ENTER_STATIC
 
@@ -1174,11 +1174,11 @@ static herr_t
 H5FD__log_read(H5FD_t *_file, H5FD_mem_t type, hid_t H5_ATTR_UNUSED dxpl_id, haddr_t addr, size_t size,
                void *buf /*out*/)
 {
-    H5FD_log_t *  file      = (H5FD_log_t *)_file;
-    size_t        orig_size = size; /* Save the original size for later */
-    haddr_t       orig_addr = addr;
-    H5_timer_t    read_timer; /* Timer for read operation */
-    H5_timevals_t read_times; /* Elapsed time for read operation */
+    H5FD_log_t *  file       = (H5FD_log_t *)_file;
+    size_t        orig_size  = size; /* Save the original size for later */
+    haddr_t       orig_addr  = addr;
+    H5_timer_t    read_timer = {{0}, {0}, {0}, FALSE}; /* Timer for read operation */
+    H5_timevals_t read_times;                          /* Elapsed time for read operation */
 #ifndef H5_HAVE_PREADWRITE
     H5_timer_t    seek_timer; /* Timer for seek operation */
     H5_timevals_t seek_times; /* Elapsed time for seek operation */
@@ -1388,11 +1388,11 @@ static herr_t
 H5FD__log_write(H5FD_t *_file, H5FD_mem_t type, hid_t H5_ATTR_UNUSED dxpl_id, haddr_t addr, size_t size,
                 const void *buf)
 {
-    H5FD_log_t *  file      = (H5FD_log_t *)_file;
-    size_t        orig_size = size; /* Save the original size for later */
-    haddr_t       orig_addr = addr;
-    H5_timer_t    write_timer; /* Timer for write operation */
-    H5_timevals_t write_times; /* Elapsed time for write operation */
+    H5FD_log_t *  file        = (H5FD_log_t *)_file;
+    size_t        orig_size   = size; /* Save the original size for later */
+    haddr_t       orig_addr   = addr;
+    H5_timer_t    write_timer = {{0}, {0}, {0}, FALSE}; /* Timer for write operation */
+    H5_timevals_t write_times;                          /* Elapsed time for write operation */
 #ifndef H5_HAVE_PREADWRITE
     H5_timer_t    seek_timer; /* Timer for seek operation */
     H5_timevals_t seek_times; /* Elapsed time for seek operation */
@@ -1612,8 +1612,8 @@ H5FD__log_truncate(H5FD_t *_file, hid_t H5_ATTR_UNUSED dxpl_id, hbool_t H5_ATTR_
 
     /* Extend the file to make sure it's large enough */
     if (!H5F_addr_eq(file->eoa, file->eof)) {
-        H5_timer_t    trunc_timer; /* Timer for truncate operation */
-        H5_timevals_t trunc_times; /* Elapsed time for truncate operation */
+        H5_timer_t    trunc_timer = {{0}, {0}, {0}, FALSE}; /* Timer for truncate operation */
+        H5_timevals_t trunc_times;                          /* Elapsed time for truncate operation */
 
         /* Start timer for truncate operation */
         if (file->fa.flags & H5FD_LOG_TIME_TRUNCATE) {
diff --git a/src/H5FDmulti.c b/src/H5FDmulti.c
index cc9f51d..b61b193 100644
--- a/src/H5FDmulti.c
+++ b/src/H5FDmulti.c
@@ -1822,8 +1822,8 @@ H5FD_multi_lock(H5FD_t *_file, hbool_t rw)
 {
     H5FD_multi_t *     file    = (H5FD_multi_t *)_file;
     int                nerrors = 0;
-    H5FD_mem_t         out_mt;
-    static const char *func = "H5FD_multi_unlock"; /* Function Name for error reporting */
+    H5FD_mem_t         out_mt  = H5FD_MEM_DEFAULT;
+    static const char *func    = "H5FD_multi_unlock"; /* Function Name for error reporting */
 
     /* Clear the error stack */
     H5Eclear2(H5E_DEFAULT);
diff --git a/src/H5FSsection.c b/src/H5FSsection.c
index af2f4d0..6ba1bc3 100644
--- a/src/H5FSsection.c
+++ b/src/H5FSsection.c
@@ -1154,8 +1154,8 @@ H5FS__sect_merge(H5FS_t *fspace, H5FS_section_info_t **sect, void *op_data)
     /* Loop until no more merging */
     if (fspace->sinfo->merge_list) {
         do {
-            H5SL_node_t *         less_sect_node;    /* Skip list node for section less than new section */
-            H5SL_node_t *         greater_sect_node; /* Skip list node for section greater than new section */
+            H5SL_node_t *less_sect_node;             /* Skip list node for section less than new section */
+            H5SL_node_t *greater_sect_node = NULL;   /* Skip list node for section greater than new section */
             H5FS_section_info_t * tmp_sect;          /* Temporary free space section */
             H5FS_section_class_t *tmp_sect_cls;      /* Temporary section's class */
             hbool_t greater_sect_node_valid = FALSE; /* Indicate if 'greater than' section node is valid */
diff --git a/src/H5HFdbg.c b/src/H5HFdbg.c
index f860881..cc61aa1 100644
--- a/src/H5HFdbg.c
+++ b/src/H5HFdbg.c
@@ -690,10 +690,10 @@ herr_t
 H5HF_iblock_debug(H5F_t *f, haddr_t addr, FILE *stream, int indent, int fwidth, haddr_t hdr_addr,
                   unsigned nrows)
 {
-    H5HF_hdr_t *     hdr    = NULL;       /* Fractal heap header info */
-    H5HF_indirect_t *iblock = NULL;       /* Fractal heap direct block info */
-    hbool_t          did_protect;         /* Whether we protected the indirect block or not */
-    herr_t           ret_value = SUCCEED; /* Return value */
+    H5HF_hdr_t *     hdr         = NULL;    /* Fractal heap header info */
+    H5HF_indirect_t *iblock      = NULL;    /* Fractal heap direct block info */
+    hbool_t          did_protect = FALSE;   /* Whether we protected the indirect block or not */
+    herr_t           ret_value   = SUCCEED; /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
 
diff --git a/src/H5HFman.c b/src/H5HFman.c
index b516790..427be00 100644
--- a/src/H5HFman.c
+++ b/src/H5HFman.c
@@ -297,9 +297,9 @@ H5HF__man_op_real(H5HF_hdr_t *hdr, const uint8_t *id, H5HF_operator_t op, void *
                                          * H5AC__NO_FLAGS_SET or
                                          * H5AC__READ_ONLY_FLAG
                                          */
-    haddr_t  dblock_addr;               /* Direct block address */
+    haddr_t  dblock_addr = HADDR_UNDEF; /* Direct block address */
     size_t   dblock_size;               /* Direct block size */
-    unsigned dblock_cache_flags;        /* Flags for unprotecting direct block */
+    unsigned dblock_cache_flags = 0;    /* Flags for unprotecting direct block */
     hsize_t  obj_off;                   /* Object's offset in heap */
     size_t   obj_len;                   /* Object's length in heap */
     size_t   blk_off;                   /* Offset of object in block */
@@ -545,9 +545,9 @@ done:
 herr_t
 H5HF__man_remove(H5HF_hdr_t *hdr, const uint8_t *id)
 {
-    H5HF_free_section_t *sec_node = NULL;     /* Pointer to free space section for block */
-    H5HF_indirect_t *    iblock   = NULL;     /* Pointer to indirect block */
-    hbool_t              did_protect;         /* Whether we protected the indirect block or not */
+    H5HF_free_section_t *sec_node    = NULL;  /* Pointer to free space section for block */
+    H5HF_indirect_t *    iblock      = NULL;  /* Pointer to indirect block */
+    hbool_t              did_protect = FALSE; /* Whether we protected the indirect block or not */
     hsize_t              obj_off;             /* Object's offset in heap */
     size_t               obj_len;             /* Object's length in heap */
     size_t               dblock_size;         /* Direct block size */
diff --git a/src/H5HFsection.c b/src/H5HFsection.c
index be4ce2c..eec41a4 100644
--- a/src/H5HFsection.c
+++ b/src/H5HFsection.c
@@ -2475,7 +2475,7 @@ H5HF__sect_indirect_init_rows(H5HF_hdr_t *hdr, H5HF_free_section_t *sect, hbool_
 
             /* Add an indirect section for each indirect block in the row */
             for (v = 0; v < row_entries; v++) {
-                hbool_t did_protect; /* Whether we protected the indirect block or not */
+                hbool_t did_protect = FALSE; /* Whether we protected the indirect block or not */
 
                 /* Try to get the child section's indirect block, if it's available */
                 if (sect->sect_info.state == H5FS_SECT_LIVE) {
diff --git a/src/H5HL.c b/src/H5HL.c
index e277779..50d24c3 100644
--- a/src/H5HL.c
+++ b/src/H5HL.c
@@ -930,7 +930,7 @@ BEGIN_FUNC(PRIV, ERR, herr_t, SUCCEED, FAIL, H5HL_get_size(H5F_t *f, haddr_t add
 
     H5HL_cache_prfx_ud_t prfx_udata;  /* User data for protecting local heap prefix */
     H5HL_prfx_t *        prfx = NULL; /* Local heap prefix */
-    H5HL_t *             heap;        /* Heap data structure */
+    H5HL_t *             heap = NULL; /* Heap data structure */
 
     /* check arguments */
     HDassert(f);
@@ -977,7 +977,7 @@ BEGIN_FUNC(PRIV, ERR, herr_t, SUCCEED, FAIL, H5HL_heapsize(H5F_t *f, haddr_t add
 
     H5HL_cache_prfx_ud_t prfx_udata;  /* User data for protecting local heap prefix */
     H5HL_prfx_t *        prfx = NULL; /* Local heap prefix */
-    H5HL_t *             heap;        /* Heap data structure */
+    H5HL_t *             heap = NULL; /* Heap data structure */
 
     /* check arguments */
     HDassert(f);
diff --git a/src/H5MF.c b/src/H5MF.c
index 720f0e4..16da9e6 100644
--- a/src/H5MF.c
+++ b/src/H5MF.c
@@ -3081,16 +3081,16 @@ done:
 herr_t
 H5MF_settle_meta_data_fsm(H5F_t *f, hbool_t *fsm_settled)
 {
-    H5F_mem_page_t sm_fshdr_fs_type;                /* small fs hdr fsm */
-    H5F_mem_page_t sm_fssinfo_fs_type;              /* small fs sinfo fsm */
-    H5F_mem_page_t lg_fshdr_fs_type;                /* large fs hdr fsm */
-    H5F_mem_page_t lg_fssinfo_fs_type;              /* large fs sinfo fsm */
-    H5FS_t *       sm_hdr_fspace   = NULL;          /* ptr to sm FSM hdr alloc FSM */
-    H5FS_t *       sm_sinfo_fspace = NULL;          /* ptr to sm FSM sinfo alloc FSM */
-    H5FS_t *       lg_hdr_fspace   = NULL;          /* ptr to lg FSM hdr alloc FSM */
-    H5FS_t *       lg_sinfo_fspace = NULL;          /* ptr to lg FSM sinfo alloc FSM */
-    haddr_t        eoa_fsm_fsalloc;                 /* eoa after file space allocation */
-                                                    /* for self referential FSMs */
+    H5F_mem_page_t sm_fshdr_fs_type;                          /* small fs hdr fsm */
+    H5F_mem_page_t sm_fssinfo_fs_type;                        /* small fs sinfo fsm */
+    H5F_mem_page_t lg_fshdr_fs_type   = H5F_MEM_PAGE_DEFAULT; /* large fs hdr fsm */
+    H5F_mem_page_t lg_fssinfo_fs_type = H5F_MEM_PAGE_DEFAULT; /* large fs sinfo fsm */
+    H5FS_t *       sm_hdr_fspace      = NULL;                 /* ptr to sm FSM hdr alloc FSM */
+    H5FS_t *       sm_sinfo_fspace    = NULL;                 /* ptr to sm FSM sinfo alloc FSM */
+    H5FS_t *       lg_hdr_fspace      = NULL;                 /* ptr to lg FSM hdr alloc FSM */
+    H5FS_t *       lg_sinfo_fspace    = NULL;                 /* ptr to lg FSM sinfo alloc FSM */
+    haddr_t        eoa_fsm_fsalloc;                           /* eoa after file space allocation */
+                                                              /* for self referential FSMs */
     hbool_t     continue_alloc_fsm = FALSE;         /* Continue allocating addr and sect_addr for FSMs */
     H5AC_ring_t orig_ring          = H5AC_RING_INV; /* Original ring value */
     herr_t      ret_value          = SUCCEED;       /* Return value */
diff --git a/src/H5Oalloc.c b/src/H5Oalloc.c
index 1a004a5..98bbf0b 100644
--- a/src/H5Oalloc.c
+++ b/src/H5Oalloc.c
@@ -2005,8 +2005,8 @@ H5O__merge_null(H5F_t *f, H5O_t *oh)
                 for (v = 0, curr_msg2 = &oh->mesg[0]; v < oh->nmesgs; v++, curr_msg2++) {
                     if (u != v && H5O_NULL_ID == curr_msg2->type->id &&
                         curr_msg->chunkno == curr_msg2->chunkno) {
-                        ssize_t adj_raw;      /* Amount to adjust raw message pointer */
-                        size_t  adj_raw_size; /* Amount to adjust raw message size */
+                        ssize_t adj_raw      = 0; /* Amount to adjust raw message pointer */
+                        size_t  adj_raw_size = 0; /* Amount to adjust raw message size */
 
                         /* Check for second message after first message */
                         if ((curr_msg->raw + curr_msg->raw_size) ==
diff --git a/src/H5Obtreek.c b/src/H5Obtreek.c
index 8656b81..a783366 100644
--- a/src/H5Obtreek.c
+++ b/src/H5Obtreek.c
@@ -198,7 +198,7 @@ static size_t
 H5O__btreek_size(const H5F_t H5_ATTR_UNUSED *f, hbool_t H5_ATTR_UNUSED disable_shared,
                  const void H5_ATTR_UNUSED *_mesg)
 {
-    size_t ret_value;
+    size_t ret_value = 0;
 
     FUNC_ENTER_STATIC_NOERR
 
diff --git a/src/H5PB.c b/src/H5PB.c
index 5ea45d9..efaf1f9 100644
--- a/src/H5PB.c
+++ b/src/H5PB.c
@@ -682,8 +682,8 @@ H5PB_read(H5F_shared_t *f_sh, H5FD_mem_t type, haddr_t addr, size_t size, void *
     haddr_t       offset;
     haddr_t       search_addr;       /* Address of current page */
     hsize_t       num_touched_pages; /* Number of pages accessed */
-    size_t        access_size;
-    hbool_t       bypass_pb = FALSE;   /* Whether to bypass page buffering */
+    size_t        access_size = 0;
+    hbool_t       bypass_pb   = FALSE; /* Whether to bypass page buffering */
     hsize_t       i;                   /* Local index variable */
     herr_t        ret_value = SUCCEED; /* Return value */
 
@@ -983,8 +983,8 @@ H5PB_write(H5F_shared_t *f_sh, H5FD_mem_t type, haddr_t addr, size_t size, const
     haddr_t       offset;
     haddr_t       search_addr;       /* Address of current page */
     hsize_t       num_touched_pages; /* Number of pages accessed */
-    size_t        access_size;
-    hbool_t       bypass_pb = FALSE;   /* Whether to bypass page buffering */
+    size_t        access_size = 0;
+    hbool_t       bypass_pb   = FALSE; /* Whether to bypass page buffering */
     hsize_t       i;                   /* Local index variable */
     herr_t        ret_value = SUCCEED; /* Return value */
 
diff --git a/src/H5Pdapl.c b/src/H5Pdapl.c
index a86c4c6..c8a97c2 100644
--- a/src/H5Pdapl.c
+++ b/src/H5Pdapl.c
@@ -866,8 +866,8 @@ done:
 static herr_t
 H5P__encode_chunk_cache_nslots(const void *value, void **_pp, size_t *size)
 {
-    uint64_t  enc_value; /* Property value to encode */
-    uint8_t **pp = (uint8_t **)_pp;
+    uint64_t  enc_value = 0; /* Property value to encode */
+    uint8_t **pp        = (uint8_t **)_pp;
     unsigned  enc_size; /* Size of encoded property */
 
     FUNC_ENTER_STATIC_NOERR
@@ -966,8 +966,8 @@ H5P__decode_chunk_cache_nslots(const void **_pp, void *_value)
 static herr_t
 H5P__encode_chunk_cache_nbytes(const void *value, void **_pp, size_t *size)
 {
-    uint64_t  enc_value; /* Property value to encode */
-    uint8_t **pp = (uint8_t **)_pp;
+    uint64_t  enc_value = 0; /* Property value to encode */
+    uint8_t **pp        = (uint8_t **)_pp;
     unsigned  enc_size; /* Size of encoded property */
 
     FUNC_ENTER_STATIC_NOERR
diff --git a/src/H5Pdcpl.c b/src/H5Pdcpl.c
index b53576e..0768d11 100644
--- a/src/H5Pdcpl.c
+++ b/src/H5Pdcpl.c
@@ -2215,7 +2215,7 @@ herr_t
 H5Pset_virtual(hid_t dcpl_id, hid_t vspace_id, const char *src_file_name, const char *src_dset_name,
                hid_t src_space_id)
 {
-    H5P_genplist_t *           plist;                      /* Property list pointer */
+    H5P_genplist_t *           plist = NULL;               /* Property list pointer */
     H5O_layout_t               virtual_layout;             /* Layout information for setting virtual info */
     H5S_t *                    vspace;                     /* Virtual dataset space selection */
     H5S_t *                    src_space;                  /* Source dataset space selection */
diff --git a/src/H5Pfapl.c b/src/H5Pfapl.c
index ac91e1d..c085b71 100644
--- a/src/H5Pfapl.c
+++ b/src/H5Pfapl.c
@@ -4271,9 +4271,9 @@ herr_t
 H5Pget_mdc_log_options(hid_t plist_id, hbool_t *is_enabled /*out*/, char *location /*out*/,
                        size_t *location_size /*out*/, hbool_t *start_on_access /*out*/)
 {
-    H5P_genplist_t *plist;               /* Property list pointer */
-    char *          location_ptr;        /* Pointer to location string */
-    herr_t          ret_value = SUCCEED; /* Return value */
+    H5P_genplist_t *plist;                  /* Property list pointer */
+    char *          location_ptr = NULL;    /* Pointer to location string */
+    herr_t          ret_value    = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE5("e", "ixxxx", plist_id, is_enabled, location, location_size, start_on_access);
diff --git a/src/H5SL.c b/src/H5SL.c
index d461efa..166019b 100644
--- a/src/H5SL.c
+++ b/src/H5SL.c
@@ -746,10 +746,10 @@ done:
 static H5SL_node_t *
 H5SL__insert_common(H5SL_t *slist, void *item, const void *key)
 {
-    H5SL_node_t *x;           /* Current node to examine */
-    H5SL_node_t *prev;        /* Node before the new node */
-    uint32_t     hashval = 0; /* Hash value for key */
-    H5SL_node_t *ret_value;   /* Return value */
+    H5SL_node_t *x;                /* Current node to examine */
+    H5SL_node_t *prev;             /* Node before the new node */
+    uint32_t     hashval   = 0;    /* Hash value for key */
+    H5SL_node_t *ret_value = NULL; /* Return value */
 
     FUNC_ENTER_STATIC
 
@@ -1378,9 +1378,9 @@ done:
 void *
 H5SL_search(H5SL_t *slist, const void *key)
 {
-    H5SL_node_t *x;           /* Current node to examine */
-    uint32_t     hashval = 0; /* Hash value for key */
-    void *       ret_value;   /* Return value */
+    H5SL_node_t *x;                /* Current node to examine */
+    uint32_t     hashval   = 0;    /* Hash value for key */
+    void *       ret_value = NULL; /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT_NOERR
 
@@ -1676,9 +1676,9 @@ done:
 H5SL_node_t *
 H5SL_find(H5SL_t *slist, const void *key)
 {
-    H5SL_node_t *x;           /* Current node to examine */
-    uint32_t     hashval = 0; /* Hash value for key */
-    H5SL_node_t *ret_value;   /* Return value */
+    H5SL_node_t *x;                /* Current node to examine */
+    uint32_t     hashval   = 0;    /* Hash value for key */
+    H5SL_node_t *ret_value = NULL; /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT_NOERR
 
diff --git a/src/H5Shyper.c b/src/H5Shyper.c
index 3f2991f..8777661 100644
--- a/src/H5Shyper.c
+++ b/src/H5Shyper.c
@@ -1104,10 +1104,10 @@ H5S__hyper_iter_next(H5S_sel_iter_t *iter, size_t nelem)
     } /* end if */
     /* Must be an irregular hyperslab selection */
     else {
-        H5S_hyper_span_t * curr_span; /* Current hyperslab span node */
-        H5S_hyper_span_t **ispan;     /* Iterator's hyperslab span nodes */
-        hsize_t *          abs_arr;   /* Absolute hyperslab span position */
-        int                curr_dim;  /* Temporary rank holder */
+        H5S_hyper_span_t * curr_span = NULL; /* Current hyperslab span node */
+        H5S_hyper_span_t **ispan;            /* Iterator's hyperslab span nodes */
+        hsize_t *          abs_arr;          /* Absolute hyperslab span position */
+        int                curr_dim;         /* Temporary rank holder */
 
         /* Set the rank of the fastest changing dimension */
         ndims    = iter->rank;
@@ -1296,10 +1296,10 @@ H5S__hyper_iter_next_block(H5S_sel_iter_t *iter)
     } /* end if */
     /* Must be an irregular hyperslab selection */
     else {
-        H5S_hyper_span_t * curr_span; /* Current hyperslab span node */
-        H5S_hyper_span_t **ispan;     /* Iterator's hyperslab span nodes */
-        hsize_t *          abs_arr;   /* Absolute hyperslab span position */
-        int                curr_dim;  /* Temporary rank holder */
+        H5S_hyper_span_t * curr_span = NULL; /* Current hyperslab span node */
+        H5S_hyper_span_t **ispan;            /* Iterator's hyperslab span nodes */
+        hsize_t *          abs_arr;          /* Absolute hyperslab span position */
+        int                curr_dim;         /* Temporary rank holder */
 
         /* Set the rank of the fastest changing dimension */
         ndims    = iter->rank;
diff --git a/src/H5VLnative_blob.c b/src/H5VLnative_blob.c
index 4fa8a2a..170a5bc 100644
--- a/src/H5VLnative_blob.c
+++ b/src/H5VLnative_blob.c
@@ -104,7 +104,7 @@ H5VL__native_blob_get(void *obj, const void *blob_id, void *buf, size_t size, vo
     H5F_t *        f  = (H5F_t *)obj;             /* Retrieve file pointer */
     const uint8_t *id = (const uint8_t *)blob_id; /* Pointer to the disk blob ID */
     H5HG_t         hobjid;                        /* Global heap ID for sequence */
-    size_t         hobj_size;                     /* Global heap object size returned from H5HG_read() */
+    size_t         hobj_size = 0;                 /* Global heap object size returned from H5HG_read() */
     herr_t         ret_value = SUCCEED;           /* Return value */
 
     FUNC_ENTER_PACKAGE
diff --git a/src/H5system.c b/src/H5system.c
index 939672a..2ac3f93 100644
--- a/src/H5system.c
+++ b/src/H5system.c
@@ -986,7 +986,7 @@ done:
 herr_t
 H5_combine_path(const char *path1, const char *path2, char **full_name /*out*/)
 {
-    size_t path1_len;           /* length of path1 */
+    size_t path1_len = 0;       /* length of path1 */
     size_t path2_len;           /* length of path2 */
     herr_t ret_value = SUCCEED; /* Return value */
 
diff --git a/src/H5timer.c b/src/H5timer.c
index f478822..54a3365 100644
--- a/src/H5timer.c
+++ b/src/H5timer.c
@@ -583,10 +583,10 @@ H5_timer_get_time_string(double seconds)
     char *s; /* output string */
 
     /* Used when the time is greater than 59 seconds */
-    double days;
-    double hours;
-    double minutes;
-    double remainder_sec;
+    double days          = 0.0;
+    double hours         = 0.0;
+    double minutes       = 0.0;
+    double remainder_sec = 0.0;
 
     /* Extract larger time units from count of seconds */
     if (seconds > (double)60.0F) {
diff --git a/src/H5trace.c b/src/H5trace.c
index e807a9f..aa9cfd4 100644
--- a/src/H5trace.c
+++ b/src/H5trace.c
@@ -3883,7 +3883,7 @@ H5_trace(const double *returning, const char *func, const char *type, ...)
     hssize_t          i;
     FILE *            out                 = H5_debug_g.trace;
     static hbool_t    is_first_invocation = TRUE;
-    H5_timer_t        function_timer;
+    H5_timer_t        function_timer      = {{0}, {0}, {0}, FALSE};
     H5_timevals_t     function_times;
     static H5_timer_t running_timer;
     H5_timevals_t     running_times;
diff --git a/tools/lib/h5tools.c b/tools/lib/h5tools.c
index f6566d9..3b78491 100644
--- a/tools/lib/h5tools.c
+++ b/tools/lib/h5tools.c
@@ -1778,7 +1778,7 @@ render_bin_output(FILE *stream, hid_t container, hid_t tid, void *_mem, hsize_t
         } break;
         case H5T_ARRAY: {
             int     k, ndims;
-            hsize_t dims[H5S_MAX_RANK], temp_nelmts, nelmts;
+            hsize_t dims[H5S_MAX_RANK], temp_nelmts, nelmts = 0;
             hid_t   memb = H5I_INVALID_HID;
 
             H5TOOLS_DEBUG("H5T_ARRAY");
diff --git a/tools/src/h5ls/h5ls.c b/tools/src/h5ls/h5ls.c
index f718bde..09bc323 100644
--- a/tools/src/h5ls/h5ls.c
+++ b/tools/src/h5ls/h5ls.c
@@ -2648,7 +2648,7 @@ int
 main(int argc, const char *argv[])
 {
     hid_t              file_id = H5I_INVALID_HID;
-    char *             fname = NULL, *oname = NULL, *x;
+    char *             fname = NULL, *oname = NULL, *x = NULL;
     const char *       s = NULL;
     char *             rest;
     int                argno;
diff --git a/tools/src/misc/h5debug.c b/tools/src/misc/h5debug.c
index e95919f..454981d 100644
--- a/tools/src/misc/h5debug.c
+++ b/tools/src/misc/h5debug.c
@@ -246,8 +246,8 @@ main(int argc, char *argv[])
     haddr_t        extra[10];
     uint8_t        sig[H5F_SIGNATURE_LEN];
     size_t         u;
-    H5E_auto2_t    func;
-    void *         edata;
+    H5E_auto2_t    func           = NULL;
+    void *         edata          = NULL;
     hbool_t        api_ctx_pushed = FALSE; /* Whether API context pushed */
     herr_t         status         = SUCCEED;
     int            exit_value     = 0;
diff --git a/tools/src/misc/h5repart.c b/tools/src/misc/h5repart.c
index 77b40a1..a75f6d8 100644
--- a/tools/src/misc/h5repart.c
+++ b/tools/src/misc/h5repart.c
@@ -97,7 +97,7 @@ static off_t
 get_size(const char *progname, int *argno, int argc, char *argv[])
 {
     off_t retval = -1;
-    char *suffix;
+    char *suffix = NULL;
 
     if (isdigit((int)(argv[*argno][2]))) {
         retval = HDstrtol(argv[*argno] + 2, &suffix, 10);