diff --git a/glib/garray.c b/glib/garray.c
index b44156215..1ab3beeda 100644
--- a/glib/garray.c
+++ b/glib/garray.c
@@ -936,7 +936,7 @@ g_array_binary_search (GArray        *array,
 {
   gboolean result = FALSE;
   GRealArray *_array = (GRealArray *) array;
-  guint left, middle, right;
+  guint left, middle = 0, right;
   gint val;
 
   g_return_val_if_fail (_array != NULL, FALSE);
diff --git a/glib/gconvert.c b/glib/gconvert.c
index cb0dcaa01..e51537881 100644
--- a/glib/gconvert.c
+++ b/glib/gconvert.c
@@ -1420,7 +1420,7 @@ static const guchar acceptable[96] = {
   0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x20,0x20,0x20,0x3F,0x20
 };
 
-static const gchar hex[16] = "0123456789ABCDEF";
+static const gchar hex[] = "0123456789ABCDEF";
 
 /* Note: This escape function works on file: URIs, but if you want to
  * escape something else, please read RFC-2396 */
diff --git a/glib/gdatetime.c b/glib/gdatetime.c
index 429cadefc..142338128 100644
--- a/glib/gdatetime.c
+++ b/glib/gdatetime.c
@@ -622,7 +622,7 @@ g_date_time_get_week_number (GDateTime *datetime,
                              gint      *day_of_week,
                              gint      *day_of_year)
 {
-  gint a, b, c, d, e, f, g, n, s, month, day, year;
+  gint a, b, c, d, e, f, g, n, s, month = -1, day = -1, year = -1;
 
   g_date_time_get_ymd (datetime, &year, &month, &day);
 
@@ -2342,7 +2342,7 @@ g_date_time_get_day_of_month (GDateTime *datetime)
 gint
 g_date_time_get_week_numbering_year (GDateTime *datetime)
 {
-  gint year, month, day, weekday;
+  gint year = -1, month = -1, day = -1, weekday;
 
   g_date_time_get_ymd (datetime, &year, &month, &day);
   weekday = g_date_time_get_day_of_week (datetime);
diff --git a/glib/giowin32.c b/glib/giowin32.c
index 72cd9220c..7282e1a54 100644
--- a/glib/giowin32.c
+++ b/glib/giowin32.c
@@ -815,7 +815,7 @@ g_io_win32_check (GSource *source)
   GIOWin32Watch *watch = (GIOWin32Watch *)source;
   GIOWin32Channel *channel = (GIOWin32Channel *)watch->channel;
   GIOCondition buffer_condition = g_io_channel_get_buffer_condition (watch->channel);
-  WSANETWORKEVENTS events;
+  WSANETWORKEVENTS events = { 0 };
 
   if (channel->debug)
     g_print ("g_io_win32_check: source=%p channel=%p", source, channel);
@@ -1452,7 +1452,7 @@ g_io_win32_sock_read (GIOChannel *channel,
   GIOWin32Channel *win32_channel = (GIOWin32Channel *)channel;
   gint result;
   GIOChannelError error;
-  int winsock_error;
+  int winsock_error = 0;
 
   if (win32_channel->debug)
     g_print ("g_io_win32_sock_read: channel=%p sock=%d count=%" G_GSIZE_FORMAT,
@@ -1513,8 +1513,8 @@ g_io_win32_sock_write (GIOChannel  *channel,
   GIOWin32Channel *win32_channel = (GIOWin32Channel *)channel;
   gint result;
   GIOChannelError error;
-  int winsock_error;
-  
+  int winsock_error = 0;
+
   if (win32_channel->debug)
     g_print ("g_io_win32_sock_write: channel=%p sock=%d count=%" G_GSIZE_FORMAT,
 	     channel, win32_channel->fd, count);
diff --git a/glib/gmarkup.c b/glib/gmarkup.c
index b8327fb6d..cfebed3e2 100644
--- a/glib/gmarkup.c
+++ b/glib/gmarkup.c
@@ -1032,7 +1032,7 @@ emit_start_element (GMarkupParseContext  *context,
    */
   if ((context->flags & G_MARKUP_IGNORE_QUALIFIED) && strchr (current_element (context), ':'))
     {
-      static const GMarkupParser ignore_parser;
+      static const GMarkupParser ignore_parser = { 0 };
       g_markup_parse_context_push (context, &ignore_parser, NULL);
       clear_attributes (context);
       return;
diff --git a/glib/gslice.c b/glib/gslice.c
index 353f55c47..4e999202e 100644
--- a/glib/gslice.c
+++ b/glib/gslice.c
@@ -610,8 +610,8 @@ magazine_count (ChunkLink *head)
 #endif
 
 static inline gsize
-allocator_get_magazine_threshold (Allocator *allocator,
-                                  guint      ix)
+allocator_get_magazine_threshold (Allocator *local_allocator,
+                                  guint ix)
 {
   /* the magazine size calculated here has a lower bound of MIN_MAGAZINE_SIZE,
    * which is required by the implementation. also, for moderately sized chunks
@@ -622,9 +622,9 @@ allocator_get_magazine_threshold (Allocator *allocator,
    * MAX_MAGAZINE_SIZE. for larger chunks, this number is scaled down so that
    * the content of a single magazine doesn't exceed ca. 16KB.
    */
-  gsize chunk_size = SLAB_CHUNK_SIZE (allocator, ix);
-  guint threshold = MAX (MIN_MAGAZINE_SIZE, allocator->max_page_size / MAX (5 * chunk_size, 5 * 32));
-  guint contention_counter = allocator->contention_counters[ix];
+  gsize chunk_size = SLAB_CHUNK_SIZE (local_allocator, ix);
+  guint threshold = MAX (MIN_MAGAZINE_SIZE, local_allocator->max_page_size / MAX (5 * chunk_size, 5 * 32));
+  guint contention_counter = local_allocator->contention_counters[ix];
   if (G_UNLIKELY (contention_counter))  /* single CPU bias */
     {
       /* adapt contention counter thresholds to chunk sizes */
@@ -676,16 +676,16 @@ magazine_chain_prepare_fields (ChunkLink *magazine_chunks)
 #define magazine_chain_count(mc)        ((mc)->next->next->next->data)
 
 static void
-magazine_cache_trim (Allocator *allocator,
-                     guint      ix,
-                     guint      stamp)
+magazine_cache_trim (Allocator *local_allocator,
+                     guint ix,
+                     guint stamp)
 {
-  /* g_mutex_lock (allocator->mutex); done by caller */
+  /* g_mutex_lock (local_allocator->mutex); done by caller */
   /* trim magazine cache from tail */
-  ChunkLink *current = magazine_chain_prev (allocator->magazines[ix]);
+  ChunkLink *current = magazine_chain_prev (local_allocator->magazines[ix]);
   ChunkLink *trash = NULL;
-  while (!G_APPROX_VALUE(stamp, magazine_chain_uint_stamp (current),
-                         allocator->config.working_set_msecs))
+  while (!G_APPROX_VALUE (stamp, magazine_chain_uint_stamp (current),
+                          local_allocator->config.working_set_msecs))
     {
       /* unlink */
       ChunkLink *prev = magazine_chain_prev (current);
@@ -699,19 +699,19 @@ magazine_cache_trim (Allocator *allocator,
       magazine_chain_prev (current) = trash;
       trash = current;
       /* fixup list head if required */
-      if (current == allocator->magazines[ix])
+      if (current == local_allocator->magazines[ix])
         {
-          allocator->magazines[ix] = NULL;
+          local_allocator->magazines[ix] = NULL;
           break;
         }
       current = prev;
     }
-  g_mutex_unlock (&allocator->magazine_mutex);
+  g_mutex_unlock (&local_allocator->magazine_mutex);
   /* free trash */
   if (trash)
     {
-      const gsize chunk_size = SLAB_CHUNK_SIZE (allocator, ix);
-      g_mutex_lock (&allocator->slab_mutex);
+      const gsize chunk_size = SLAB_CHUNK_SIZE (local_allocator, ix);
+      g_mutex_lock (&local_allocator->slab_mutex);
       while (trash)
         {
           current = trash;
@@ -723,7 +723,7 @@ magazine_cache_trim (Allocator *allocator,
               slab_allocator_free_chunk (chunk_size, chunk);
             }
         }
-      g_mutex_unlock (&allocator->slab_mutex);
+      g_mutex_unlock (&local_allocator->slab_mutex);
     }
 }
 
@@ -1282,40 +1282,40 @@ g_slice_free_chain_with_offset (gsize    mem_size,
 
 /* --- single page allocator --- */
 static void
-allocator_slab_stack_push (Allocator *allocator,
-                           guint      ix,
-                           SlabInfo  *sinfo)
+allocator_slab_stack_push (Allocator *local_allocator,
+                           guint ix,
+                           SlabInfo *sinfo)
 {
   /* insert slab at slab ring head */
-  if (!allocator->slab_stack[ix])
+  if (!local_allocator->slab_stack[ix])
     {
       sinfo->next = sinfo;
       sinfo->prev = sinfo;
     }
   else
     {
-      SlabInfo *next = allocator->slab_stack[ix], *prev = next->prev;
+      SlabInfo *next = local_allocator->slab_stack[ix], *prev = next->prev;
       next->prev = sinfo;
       prev->next = sinfo;
       sinfo->next = next;
       sinfo->prev = prev;
     }
-  allocator->slab_stack[ix] = sinfo;
+  local_allocator->slab_stack[ix] = sinfo;
 }
 
 static gsize
-allocator_aligned_page_size (Allocator *allocator,
-                             gsize      n_bytes)
+allocator_aligned_page_size (Allocator *local_allocator,
+                             gsize n_bytes)
 {
   gsize val = (gsize) 1 << g_bit_storage (n_bytes - 1);
-  val = MAX (val, allocator->min_page_size);
+  val = MAX (val, local_allocator->min_page_size);
   return val;
 }
 
 static void
-allocator_add_slab (Allocator *allocator,
-                    guint      ix,
-                    gsize      chunk_size)
+allocator_add_slab (Allocator *local_allocator,
+                    guint ix,
+                    gsize chunk_size)
 {
   ChunkLink *chunk;
   SlabInfo *sinfo;
@@ -1326,7 +1326,7 @@ allocator_add_slab (Allocator *allocator,
   guint8 *mem;
   guint i;
 
-  page_size = allocator_aligned_page_size (allocator, SLAB_BPAGE_SIZE (allocator, chunk_size));
+  page_size = allocator_aligned_page_size (local_allocator, SLAB_BPAGE_SIZE (local_allocator, chunk_size));
   /* allocate 1 page for the chunks and the slab */
   aligned_memory = allocator_memalign (page_size, page_size - NATIVE_MALLOC_PADDING);
   errsv = errno;
@@ -1351,8 +1351,8 @@ allocator_add_slab (Allocator *allocator,
   padding = ((guint8*) sinfo - mem) - n_chunks * chunk_size;
   if (padding)
     {
-      color = (allocator->color_accu * P2ALIGNMENT) % padding;
-      allocator->color_accu += allocator->config.color_increment;
+      color = (local_allocator->color_accu * P2ALIGNMENT) % padding;
+      local_allocator->color_accu += local_allocator->config.color_increment;
     }
   /* add chunks to free list */
   chunk = (ChunkLink*) (mem + color);
@@ -1364,7 +1364,7 @@ allocator_add_slab (Allocator *allocator,
     }
   chunk->next = NULL;   /* last chunk */
   /* add slab to slab ring */
-  allocator_slab_stack_push (allocator, ix, sinfo);
+  allocator_slab_stack_push (local_allocator, ix, sinfo);
 }
 
 static gpointer
diff --git a/glib/gspawn-win32.c b/glib/gspawn-win32.c
index 02eddccf1..d3864d54d 100644
--- a/glib/gspawn-win32.c
+++ b/glib/gspawn-win32.c
@@ -978,7 +978,7 @@ g_spawn_sync (const gchar          *working_directory,
   gint reportpipe = -1;
   GIOChannel *outchannel = NULL;
   GIOChannel *errchannel = NULL;
-  GPollFD outfd, errfd;
+  GPollFD outfd = { -1, 0, 0 }, errfd = { -1, 0, 0 };
   GPollFD fds[2];
   gint nfds;
   gint outindex = -1;
diff --git a/glib/gtimezone.c b/glib/gtimezone.c
index 6ae1a00dc..a22f70eff 100644
--- a/glib/gtimezone.c
+++ b/glib/gtimezone.c
@@ -931,7 +931,7 @@ rules_from_windows_time_zone (const gchar   *identifier,
   TIME_ZONE_INFORMATION tzi;
   DWORD size;
   guint rules_num = 0;
-  RegTZI regtzi, regtzi_prev;
+  RegTZI regtzi = { 0 }, regtzi_prev;
   WCHAR winsyspath[MAX_PATH];
   gunichar2 *subkey_w, *subkey_dynamic_w;
 
@@ -1127,7 +1127,7 @@ find_relative_date (TimeZoneDate *buffer)
       g_date_set_dmy (&date, 1, buffer->mon, buffer->year);
       first_wday = g_date_get_weekday (&date);
 
-      if (first_wday > wday)
+      if ((guint) first_wday > wday)
         ++(buffer->week);
       /* week is 1 <= w <= 5, we need 0-based */
       days = 7 * (buffer->week - 1) + wday - first_wday;
diff --git a/glib/gunicollate.c b/glib/gunicollate.c
index dfed1041d..af62171d5 100644
--- a/glib/gunicollate.c
+++ b/glib/gunicollate.c
@@ -415,7 +415,7 @@ g_utf8_collate_key (const gchar *str,
   return result;
 #else
 
-  gsize xfrm_len;
+  gsize xfrm_len = 0;
   const gchar *charset;
   gchar *str_norm;