Fixed most compiler warnings -Wall -Wextra

repro:
  CFLAGS="-Wall -Wextra -Wunused-parameter -Wc++-compat" ./configure && make

which we use for perl, and libyaml is now included in cperl.
Tested with gcc-5 and clang-3.7

There are still a tons of format warnings (%d on 64bit) in
example-deconstructor.c which I skipped.

7 files changed, 78 insertions, 58 deletions

diff --git a/src/api.c b/src/api.c
index b1a8da0..ee170d8 100644
--- a/src/api.c
+++ b/src/api.c
@@ -74,7 +74,7 @@ YAML_DECLARE(int)
 yaml_string_extend(yaml_char_t **start,
         yaml_char_t **pointer, yaml_char_t **end)
 {
-    yaml_char_t *new_start = yaml_realloc(*start, (*end - *start)*2);
+    yaml_char_t *new_start = (yaml_char_t *)yaml_realloc((void*)*start, (*end - *start)*2);
 
     if (!new_start) return 0;
 
@@ -94,8 +94,9 @@ yaml_string_extend(yaml_char_t **start,
 YAML_DECLARE(int)
 yaml_string_join(
         yaml_char_t **a_start, yaml_char_t **a_pointer, yaml_char_t **a_end,
-        yaml_char_t **b_start, yaml_char_t **b_pointer, yaml_char_t **b_end)
+        yaml_char_t **b_start, yaml_char_t **b_pointer, SHIM(yaml_char_t **b_end))
 {
+    UNUSED_PARAM(b_end)
     if (*b_start == *b_pointer)
         return 1;
 
@@ -177,17 +178,17 @@ yaml_parser_initialize(yaml_parser_t *parser)
         goto error;
     if (!BUFFER_INIT(parser, parser->buffer, INPUT_BUFFER_SIZE))
         goto error;
-    if (!QUEUE_INIT(parser, parser->tokens, INITIAL_QUEUE_SIZE))
+    if (!QUEUE_INIT(parser, parser->tokens, INITIAL_QUEUE_SIZE, yaml_token_t*))
         goto error;
-    if (!STACK_INIT(parser, parser->indents, INITIAL_STACK_SIZE))
+    if (!STACK_INIT(parser, parser->indents, int*))
         goto error;
-    if (!STACK_INIT(parser, parser->simple_keys, INITIAL_STACK_SIZE))
+    if (!STACK_INIT(parser, parser->simple_keys, yaml_simple_key_t*))
         goto error;
-    if (!STACK_INIT(parser, parser->states, INITIAL_STACK_SIZE))
+    if (!STACK_INIT(parser, parser->states, yaml_parser_state_t*))
         goto error;
-    if (!STACK_INIT(parser, parser->marks, INITIAL_STACK_SIZE))
+    if (!STACK_INIT(parser, parser->marks, yaml_mark_t*))
         goto error;
-    if (!STACK_INIT(parser, parser->tag_directives, INITIAL_STACK_SIZE))
+    if (!STACK_INIT(parser, parser->tag_directives, yaml_tag_directive_t*))
         goto error;
 
     return 1;
@@ -243,7 +244,7 @@ static int
 yaml_string_read_handler(void *data, unsigned char *buffer, size_t size,
         size_t *size_read)
 {
-    yaml_parser_t *parser = data;
+    yaml_parser_t *parser = (yaml_parser_t *)data;
 
     if (parser->input.string.current == parser->input.string.end) {
         *size_read = 0;
@@ -269,7 +270,7 @@ static int
 yaml_file_read_handler(void *data, unsigned char *buffer, size_t size,
         size_t *size_read)
 {
-    yaml_parser_t *parser = data;
+    yaml_parser_t *parser = (yaml_parser_t *)data;
 
     *size_read = fread(buffer, 1, size, parser->input.file);
     return !ferror(parser->input.file);
@@ -355,13 +356,13 @@ yaml_emitter_initialize(yaml_emitter_t *emitter)
         goto error;
     if (!BUFFER_INIT(emitter, emitter->raw_buffer, OUTPUT_RAW_BUFFER_SIZE))
         goto error;
-    if (!STACK_INIT(emitter, emitter->states, INITIAL_STACK_SIZE))
+    if (!STACK_INIT(emitter, emitter->states, yaml_emitter_state_t*))
         goto error;
-    if (!QUEUE_INIT(emitter, emitter->events, INITIAL_QUEUE_SIZE))
+    if (!QUEUE_INIT(emitter, emitter->events, INITIAL_QUEUE_SIZE, yaml_event_t*))
         goto error;
-    if (!STACK_INIT(emitter, emitter->indents, INITIAL_STACK_SIZE))
+    if (!STACK_INIT(emitter, emitter->indents, int*))
         goto error;
-    if (!STACK_INIT(emitter, emitter->tag_directives, INITIAL_STACK_SIZE))
+    if (!STACK_INIT(emitter, emitter->tag_directives, yaml_tag_directive_t*))
         goto error;
 
     return 1;
@@ -413,7 +414,7 @@ yaml_emitter_delete(yaml_emitter_t *emitter)
 static int
 yaml_string_write_handler(void *data, unsigned char *buffer, size_t size)
 {
-    yaml_emitter_t *emitter = data;
+  yaml_emitter_t *emitter = (yaml_emitter_t *)data;
 
     if (emitter->output.string.size - *emitter->output.string.size_written
             < size) {
@@ -439,7 +440,7 @@ yaml_string_write_handler(void *data, unsigned char *buffer, size_t size)
 static int
 yaml_file_write_handler(void *data, unsigned char *buffer, size_t size)
 {
-    yaml_emitter_t *emitter = data;
+    yaml_emitter_t *emitter = (yaml_emitter_t *)data;
 
     return (fwrite(buffer, 1, size, emitter->output.file) == size);
 }
@@ -717,7 +718,7 @@ yaml_document_start_event_initialize(yaml_event_t *event,
                             /* Valid tag directives are expected. */
 
     if (version_directive) {
-        version_directive_copy = yaml_malloc(sizeof(yaml_version_directive_t));
+        version_directive_copy = YAML_MALLOC_STATIC(yaml_version_directive_t);
         if (!version_directive_copy) goto error;
         version_directive_copy->major = version_directive->major;
         version_directive_copy->minor = version_directive->minor;
@@ -725,7 +726,7 @@ yaml_document_start_event_initialize(yaml_event_t *event,
 
     if (tag_directives_start != tag_directives_end) {
         yaml_tag_directive_t *tag_directive;
-        if (!STACK_INIT(&context, tag_directives_copy, INITIAL_STACK_SIZE))
+        if (!STACK_INIT(&context, tag_directives_copy, yaml_tag_directive_t*))
             goto error;
         for (tag_directive = tag_directives_start;
                 tag_directive != tag_directives_end; tag_directive ++) {
@@ -843,7 +844,7 @@ yaml_scalar_event_initialize(yaml_event_t *event,
     }
 
     if (!yaml_check_utf8(value, length)) goto error;
-    value_copy = yaml_malloc(length+1);
+    value_copy = YAML_MALLOC(length+1);
     if (!value_copy) goto error;
     memcpy(value_copy, value, length);
     value_copy[length] = '\0';
@@ -1055,10 +1056,10 @@ yaml_document_initialize(yaml_document_t *document,
             (tag_directives_start == tag_directives_end));
                             /* Valid tag directives are expected. */
 
-    if (!STACK_INIT(&context, nodes, INITIAL_STACK_SIZE)) goto error;
+    if (!STACK_INIT(&context, nodes, yaml_node_t*)) goto error;
 
     if (version_directive) {
-        version_directive_copy = yaml_malloc(sizeof(yaml_version_directive_t));
+        version_directive_copy = YAML_MALLOC_STATIC(yaml_version_directive_t);
         if (!version_directive_copy) goto error;
         version_directive_copy->major = version_directive->major;
         version_directive_copy->minor = version_directive->minor;
@@ -1066,7 +1067,7 @@ yaml_document_initialize(yaml_document_t *document,
 
     if (tag_directives_start != tag_directives_end) {
         yaml_tag_directive_t *tag_directive;
-        if (!STACK_INIT(&context, tag_directives_copy, INITIAL_STACK_SIZE))
+        if (!STACK_INIT(&context, tag_directives_copy, yaml_tag_directive_t*))
             goto error;
         for (tag_directive = tag_directives_start;
                 tag_directive != tag_directives_end; tag_directive ++) {
@@ -1219,7 +1220,7 @@ yaml_document_add_scalar(yaml_document_t *document,
     }
 
     if (!yaml_check_utf8(value, length)) goto error;
-    value_copy = yaml_malloc(length+1);
+    value_copy = YAML_MALLOC(length+1);
     if (!value_copy) goto error;
     memcpy(value_copy, value, length);
     value_copy[length] = '\0';
@@ -1266,7 +1267,7 @@ yaml_document_add_sequence(yaml_document_t *document,
     tag_copy = yaml_strdup(tag);
     if (!tag_copy) goto error;
 
-    if (!STACK_INIT(&context, items, INITIAL_STACK_SIZE)) goto error;
+    if (!STACK_INIT(&context, items, yaml_node_item_t*)) goto error;
 
     SEQUENCE_NODE_INIT(node, tag_copy, items.start, items.end,
             style, mark, mark);
@@ -1311,7 +1312,7 @@ yaml_document_add_mapping(yaml_document_t *document,
     tag_copy = yaml_strdup(tag);
     if (!tag_copy) goto error;
 
-    if (!STACK_INIT(&context, pairs, INITIAL_STACK_SIZE)) goto error;
+    if (!STACK_INIT(&context, pairs, yaml_node_pair_t*)) goto error;
 
     MAPPING_NODE_INIT(node, tag_copy, pairs.start, pairs.end,
             style, mark, mark);
diff --git a/src/dumper.c b/src/dumper.c
index 203c6a7..29fb9c0 100644
--- a/src/dumper.c
+++ b/src/dumper.c
@@ -245,9 +245,9 @@ yaml_emitter_anchor_node(yaml_emitter_t *emitter, int index)
 #define ANCHOR_TEMPLATE_LENGTH  16
 
 static yaml_char_t *
-yaml_emitter_generate_anchor(yaml_emitter_t *emitter, int anchor_id)
+yaml_emitter_generate_anchor(SHIM(yaml_emitter_t *emitter), int anchor_id)
 {
-    yaml_char_t *anchor = yaml_malloc(ANCHOR_TEMPLATE_LENGTH);
+    yaml_char_t *anchor = YAML_MALLOC(ANCHOR_TEMPLATE_LENGTH);
 
     if (!anchor) return NULL;
 
diff --git a/src/emitter.c b/src/emitter.c
index a5b7ff8..d31e075 100644
--- a/src/emitter.c
+++ b/src/emitter.c
@@ -1002,7 +1002,7 @@ yaml_emitter_emit_node(yaml_emitter_t *emitter, yaml_event_t *event,
  */
 
 static int
-yaml_emitter_emit_alias(yaml_emitter_t *emitter, yaml_event_t *event)
+yaml_emitter_emit_alias(yaml_emitter_t *emitter, SHIM(yaml_event_t *event))
 {
     if (!yaml_emitter_process_anchor(emitter))
         return 0;
@@ -1087,7 +1087,7 @@ yaml_emitter_emit_mapping_start(yaml_emitter_t *emitter, yaml_event_t *event)
  */
 
 static int
-yaml_emitter_check_empty_document(yaml_emitter_t *emitter)
+yaml_emitter_check_empty_document(SHIM(yaml_emitter_t *emitter))
 {
     return 0;
 }
diff --git a/src/loader.c b/src/loader.c
index 3ba99f0..db8501a 100644
--- a/src/loader.c
+++ b/src/loader.c
@@ -72,7 +72,7 @@ yaml_parser_load(yaml_parser_t *parser, yaml_document_t *document)
     assert(document);   /* Non-NULL document object is expected. */
 
     memset(document, 0, sizeof(yaml_document_t));
-    if (!STACK_INIT(parser, document->nodes, INITIAL_STACK_SIZE))
+    if (!STACK_INIT(parser, document->nodes, yaml_node_t*))
         goto error;
 
     if (!parser->stream_start_produced) {
@@ -90,7 +90,7 @@ yaml_parser_load(yaml_parser_t *parser, yaml_document_t *document)
         return 1;
     }
 
-    if (!STACK_INIT(parser, parser->aliases, INITIAL_STACK_SIZE))
+    if (!STACK_INIT(parser, parser->aliases, yaml_alias_data_t*))
         goto error;
 
     parser->document = document;
@@ -339,7 +339,7 @@ yaml_parser_load_sequence(yaml_parser_t *parser, yaml_event_t *first_event)
         if (!tag) goto error;
     }
 
-    if (!STACK_INIT(parser, items, INITIAL_STACK_SIZE)) goto error;
+    if (!STACK_INIT(parser, items, yaml_node_item_t*)) goto error;
 
     SEQUENCE_NODE_INIT(node, tag, items.start, items.end,
             first_event->data.sequence_start.style,
@@ -402,7 +402,7 @@ yaml_parser_load_mapping(yaml_parser_t *parser, yaml_event_t *first_event)
         if (!tag) goto error;
     }
 
-    if (!STACK_INIT(parser, pairs, INITIAL_STACK_SIZE)) goto error;
+    if (!STACK_INIT(parser, pairs, yaml_node_pair_t*)) goto error;
 
     MAPPING_NODE_INIT(node, tag, pairs.start, pairs.end,
             first_event->data.mapping_start.style,
diff --git a/src/parser.c b/src/parser.c
index dc5430b..621f676 100644
--- a/src/parser.c
+++ b/src/parser.c
@@ -605,7 +605,7 @@ yaml_parser_parse_node(yaml_parser_t *parser, yaml_event_t *event,
                     if (strcmp((char *)tag_directive->handle, (char *)tag_handle) == 0) {
                         size_t prefix_len = strlen((char *)tag_directive->prefix);
                         size_t suffix_len = strlen((char *)tag_suffix);
-                        tag = yaml_malloc(prefix_len+suffix_len+1);
+                        tag = YAML_MALLOC(prefix_len+suffix_len+1);
                         if (!tag) {
                             parser->error = YAML_MEMORY_ERROR;
                             goto error;
@@ -685,7 +685,7 @@ yaml_parser_parse_node(yaml_parser_t *parser, yaml_event_t *event,
                 return 1;
             }
             else if (anchor || tag) {
-                yaml_char_t *value = yaml_malloc(1);
+                yaml_char_t *value = YAML_MALLOC(1);
                 if (!value) {
                     parser->error = YAML_MEMORY_ERROR;
                     goto error;
@@ -759,9 +759,8 @@ yaml_parser_parse_block_sequence_entry(yaml_parser_t *parser,
 
     else if (token->type == YAML_BLOCK_END_TOKEN)
     {
-        yaml_mark_t dummy_mark;     /* Used to eliminate a compiler warning. */
         parser->state = POP(parser, parser->states);
-        dummy_mark = POP(parser, parser->marks);
+        (void)POP(parser, parser->marks);
         SEQUENCE_END_EVENT_INIT(*event, token->start_mark, token->end_mark);
         SKIP_TOKEN(parser);
         return 1;
@@ -869,9 +868,8 @@ yaml_parser_parse_block_mapping_key(yaml_parser_t *parser,
 
     else if (token->type == YAML_BLOCK_END_TOKEN)
     {
-        yaml_mark_t dummy_mark;     /* Used to eliminate a compiler warning. */
         parser->state = POP(parser, parser->states);
-        dummy_mark = POP(parser, parser->marks);
+        (void)POP(parser, parser->marks);
         MAPPING_END_EVENT_INIT(*event, token->start_mark, token->end_mark);
         SKIP_TOKEN(parser);
         return 1;
@@ -952,7 +950,6 @@ yaml_parser_parse_flow_sequence_entry(yaml_parser_t *parser,
         yaml_event_t *event, int first)
 {
     yaml_token_t *token;
-    yaml_mark_t dummy_mark;     /* Used to eliminate a compiler warning. */
 
     if (first) {
         token = PEEK_TOKEN(parser);
@@ -997,7 +994,7 @@ yaml_parser_parse_flow_sequence_entry(yaml_parser_t *parser,
     }
 
     parser->state = POP(parser, parser->states);
-    dummy_mark = POP(parser, parser->marks);
+    (void)POP(parser, parser->marks);
     SEQUENCE_END_EVENT_INIT(*event, token->start_mark, token->end_mark);
     SKIP_TOKEN(parser);
     return 1;
@@ -1104,7 +1101,6 @@ yaml_parser_parse_flow_mapping_key(yaml_parser_t *parser,
         yaml_event_t *event, int first)
 {
     yaml_token_t *token;
-    yaml_mark_t dummy_mark;     /* Used to eliminate a compiler warning. */
 
     if (first) {
         token = PEEK_TOKEN(parser);
@@ -1158,7 +1154,7 @@ yaml_parser_parse_flow_mapping_key(yaml_parser_t *parser,
     }
 
     parser->state = POP(parser, parser->states);
-    dummy_mark = POP(parser, parser->marks);
+    (void)POP(parser, parser->marks);
     MAPPING_END_EVENT_INIT(*event, token->start_mark, token->end_mark);
     SKIP_TOKEN(parser);
     return 1;
@@ -1212,7 +1208,7 @@ yaml_parser_process_empty_scalar(yaml_parser_t *parser, yaml_event_t *event,
 {
     yaml_char_t *value;
 
-    value = yaml_malloc(1);
+    value = YAML_MALLOC(1);
     if (!value) {
         parser->error = YAML_MEMORY_ERROR;
         return 0;
@@ -1249,7 +1245,7 @@ yaml_parser_process_directives(yaml_parser_t *parser,
     } tag_directives = { NULL, NULL, NULL };
     yaml_token_t *token;
 
-    if (!STACK_INIT(parser, tag_directives, INITIAL_STACK_SIZE))
+    if (!STACK_INIT(parser, tag_directives, yaml_tag_directive_t*))
         goto error;
 
     token = PEEK_TOKEN(parser);
@@ -1270,7 +1266,7 @@ yaml_parser_process_directives(yaml_parser_t *parser,
                         "found incompatible YAML document", token->start_mark);
                 goto error;
             }
-            version_directive = yaml_malloc(sizeof(yaml_version_directive_t));
+            version_directive = YAML_MALLOC_STATIC(yaml_version_directive_t);
             if (!version_directive) {
                 parser->error = YAML_MEMORY_ERROR;
                 goto error;
diff --git a/src/scanner.c b/src/scanner.c
index 068dc13..b6f5185 100644
--- a/src/scanner.c
+++ b/src/scanner.c
@@ -1186,11 +1186,9 @@ yaml_parser_increase_flow_level(yaml_parser_t *parser)
 static int
 yaml_parser_decrease_flow_level(yaml_parser_t *parser)
 {
-    yaml_simple_key_t dummy_key;    /* Used to eliminate a compiler warning. */
-
     if (parser->flow_level) {
         parser->flow_level --;
-        dummy_key = POP(parser, parser->simple_keys);
+        (void)POP(parser, parser->simple_keys);
     }
 
     return 1;
@@ -2401,7 +2399,7 @@ yaml_parser_scan_tag(yaml_parser_t *parser, yaml_token_t *token)
     {
         /* Set the handle to '' */
 
-        handle = yaml_malloc(1);
+        handle = YAML_MALLOC(1);
         if (!handle) goto error;
         handle[0] = '\0';
 
@@ -2453,7 +2451,7 @@ yaml_parser_scan_tag(yaml_parser_t *parser, yaml_token_t *token)
             /* Set the handle to '!'. */
 
             yaml_free(handle);
-            handle = yaml_malloc(2);
+            handle = YAML_MALLOC(2);
             if (!handle) goto error;
             handle[0] = '!';
             handle[1] = '\0';
diff --git a/src/yaml_private.h b/src/yaml_private.h
index 0512328..fe25141 100644
--- a/src/yaml_private.h
+++ b/src/yaml_private.h
@@ -101,7 +101,7 @@ yaml_parser_fetch_more_tokens(yaml_parser_t *parser);
  */
 
 #define BUFFER_INIT(context,buffer,size)                                        \
-    (((buffer).start = yaml_malloc(size)) ?                                     \
+  (((buffer).start = (yaml_char_t *)yaml_malloc(size)) ?                        \
         ((buffer).last = (buffer).pointer = (buffer).start,                     \
          (buffer).end = (buffer).start+(size),                                  \
          1) :                                                                   \
@@ -141,7 +141,7 @@ yaml_string_join(
      (value).pointer = (string))
 
 #define STRING_INIT(context,string,size)                                        \
-    (((string).start = yaml_malloc(size)) ?                                     \
+    (((string).start = YAML_MALLOC(size)) ?                                     \
         ((string).pointer = (string).start,                                     \
          (string).end = (string).start+(size),                                  \
          memset((string).start, 0, (size)),                                     \
@@ -431,10 +431,10 @@ yaml_stack_extend(void **start, void **top, void **end);
 YAML_DECLARE(int)
 yaml_queue_extend(void **start, void **head, void **tail, void **end);
 
-#define STACK_INIT(context,stack,size)                                          \
-    (((stack).start = yaml_malloc((size)*sizeof(*(stack).start))) ?             \
+#define STACK_INIT(context,stack,type)                                     \
+  (((stack).start = (type)yaml_malloc(INITIAL_STACK_SIZE*sizeof(*(stack).start))) ? \
         ((stack).top = (stack).start,                                           \
-         (stack).end = (stack).start+(size),                                    \
+         (stack).end = (stack).start+INITIAL_STACK_SIZE,                        \
          1) :                                                                   \
         ((context)->error = YAML_MEMORY_ERROR,                                  \
          0))
@@ -464,8 +464,8 @@ yaml_queue_extend(void **start, void **head, void **tail, void **end);
 #define POP(context,stack)                                                      \
     (*(--(stack).top))
 
-#define QUEUE_INIT(context,queue,size)                                          \
-    (((queue).start = yaml_malloc((size)*sizeof(*(queue).start))) ?             \
+#define QUEUE_INIT(context,queue,size,type)                                     \
+  (((queue).start = (type)yaml_malloc((size)*sizeof(*(queue).start))) ?         \
         ((queue).head = (queue).tail = (queue).start,                           \
          (queue).end = (queue).start+(size),                                    \
          1) :                                                                   \
@@ -668,3 +668,28 @@ yaml_queue_extend(void **start, void **head, void **tail, void **end);
      (node).data.mapping.pairs.end = (node_pairs_end),                          \
      (node).data.mapping.pairs.top = (node_pairs_start),                        \
      (node).data.mapping.style = (node_style))
+
+/* Strict C compiler warning helpers */
+
+#if defined(__clang__) || defined(__GNUC__)
+#  define HASATTRIBUTE_UNUSED
+#endif
+#ifdef HASATTRIBUTE_UNUSED
+#  define __attribute__unused__             __attribute__((__unused__))
+#else
+#  define __attribute__unused__
+#endif
+
+/* Shim arguments are arguments that must be included in your function,
+ * but serve no purpose inside.  Silence compiler warnings. */
+#define SHIM(a) /*@unused@*/ a __attribute__unused__
+
+/* UNUSED_PARAM() marks a shim argument in the body to silence compiler warnings */
+#ifdef __clang__
+#  define UNUSED_PARAM(a) (void)(a);
+#else
+#  define UNUSED_PARAM(a) /*@-noeffect*/if (0) (void)(a)/*@=noeffect*/;
+#endif
+
+#define YAML_MALLOC_STATIC(type) (type*)yaml_malloc(sizeof(type))
+#define YAML_MALLOC(size)        (yaml_char_t *)yaml_malloc(size)