[collectd 6] Compiler warnings for collectd core with stricter compilation options

[eero-t]

• Version of collectd: collectd-6.0 git
• Operating system / distribution: Fedora 38

Steps to reproduce

• Prepare config.h: ./configure
• build (most of) collectd core files with stricter warnings:

for i in $(find src/ -mindepth 3 -name '*.c' | grep -v -e /dpdk/ -e format_json.c -e format_kairosdb.c -e _mock.c -e _test.c -e _windows.c); do \
  echo "*** $i ***"; \
  gcc -I. -Isrc -Isrc/daemon -Isrc/libcollectdclient -DHAVE_CONFIG_H -O3 -Werror -Wall -Wextra -Wno-missing-field-initializers -Wcast-align=strict -Wformat-security -Wnull-dereference -Wstrict-overflow=2 -Warray-bounds=2 -D_FORTIFY_SOURCE=2 -Wno-aggressive-loop-optimizations -c -o /dev/null $i; \
done

(I do not have compatible include files for the files I've left out, and warnings from mock/test/windows files were not that relevant. Proper warning analysis requires use of high optimization level.)

Actual output

Output shows few warnings:

*** src/utils/cmds/listval.c ***
*** src/utils/cmds/putnotif.c ***
*** src/utils/cmds/putval.c ***
*** src/utils/cmds/putmetric.c ***
*** src/utils/cmds/flush.c ***
*** src/utils/cmds/parse_option.c ***
*** src/utils/cmds/getthreshold.c ***
*** src/utils/cmds/getval.c ***
*** src/utils/cmds/cmds.c ***
*** src/utils/curl_stats/curl_stats.c ***
*** src/utils/resource_metrics/resource_metrics.c ***
*** src/utils/value_list/value_list.c ***
*** src/utils/format_json/open_telemetry.c ***
*** src/utils/ignorelist/ignorelist.c ***
*** src/utils/crc32/crc32.c ***
*** src/utils/format_influxdb/format_influxdb.c ***
*** src/utils/gce/gce.c ***
*** src/utils/avltree/avltree.c ***
*** src/utils/oauth/oauth.c ***
*** src/utils/taskstats/taskstats.c ***
*** src/utils/utf8/utf8.c ***
*** src/utils/ovs/ovs.c ***
src/utils/ovs/ovs.c: In function ‘ovs_yajl_gen_val’:
src/utils/ovs/ovs.c:365:13: error: potential null pointer dereference [-Werror=null-dereference]
  365 |     obj_len = YAJL_GET_OBJECT(jval)->len;
      |     ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/utils/ovs/ovs.c:368:41: error: potential null pointer dereference [-Werror=null-dereference]
  368 |       jobj_value = YAJL_GET_OBJECT(jval)->values[i];
      |                                         ^
src/utils/ovs/ovs.c:367:38: error: null pointer dereference [-Werror=null-dereference]
  367 |       obj_key = YAJL_GET_OBJECT(jval)->keys[i];
      |                                      ^
cc1: all warnings being treated as errors
*** src/utils/heap/heap.c ***
*** src/utils/format_graphite/format_graphite.c ***
*** src/utils/rrdcreate/rrdcreate.c ***
*** src/utils/match/match.c ***
*** src/utils/tail/tail.c ***
*** src/utils/strbuf/strbuf.c ***
*** src/utils/lookup/vl_lookup.c ***
*** src/utils/message_parser/message_parser.c ***
src/utils/message_parser/message_parser.c: In function ‘start_message_assembly’:
src/utils/message_parser/message_parser.c:91:25: error: comparison of integer expressions of different signedness: ‘int’ and ‘size_t’ {aka ‘long unsigned int’} [-Werror=sign-compare]
   91 |   if (self->message_idx >= self->messages_max_len) {
      |                         ^~
src/utils/message_parser/message_parser.c: In function ‘message_assembler’:
src/utils/message_parser/message_parser.c:150:42: error: unused parameter ‘row’ [-Werror=unused-parameter]
  150 | static int message_assembler(const char *row, char *const *matches,
      |                              ~~~~~~~~~~~~^~~
cc1: all warnings being treated as errors
*** src/utils/dmi/dmi.c ***
*** src/utils/dns/dns.c ***
src/utils/dns/dns.c: In function ‘ignore_list_add_name’:
src/utils/dns/dns.c:228:16: error: cast increases required alignment of target type [-Werror=cast-align]
  228 |              &((struct sockaddr_in *)ai_ptr->ai_addr)->sin_addr, 4);
      |                ^
src/utils/dns/dns.c:232:25: error: cast increases required alignment of target type [-Werror=cast-align]
  232 |       ignore_list_add(&((struct sockaddr_in6 *)ai_ptr->ai_addr)->sin6_addr);
      |                         ^
cc1: all warnings being treated as errors
*** src/utils/db_query/db_query.c ***
*** src/utils/format_stackdriver/format_stackdriver.c ***
src/utils/format_stackdriver/format_stackdriver.c: In function ‘read_cumulative_state’:
src/utils/format_stackdriver/format_stackdriver.c:295:36: error: comparison of integer expressions of different signedness: ‘int64_t’ {aka ‘long int’} and ‘counter_t’ {aka ‘long unsigned int’} [-Werror=sign-compare]
  295 |   bool is_reset = *ret_start_value > m->value.counter;
      |                                    ^
cc1: all warnings being treated as errors
*** src/utils/metadata/meta_data.c ***
*** src/utils/common/common.c ***
*** src/utils/latency/latency.c ***
*** src/utils/latency/latency_config.c ***
*** src/utils/proc_pids/proc_pids.c ***
src/utils/proc_pids/proc_pids.c: In function ‘pids_list_contains_pid’:
src/utils/proc_pids/proc_pids.c:119:21: error: comparison of integer expressions of different signedness: ‘int’ and ‘size_t’ {aka ‘long unsigned int’} [-Werror=sign-compare]
  119 |   for (int i = 0; i < list->size; i++)
      |                     ^
src/utils/proc_pids/proc_pids.c: In function ‘pids_list_diff’:
src/utils/proc_pids/proc_pids.c:333:21: error: comparison of integer expressions of different signedness: ‘int’ and ‘size_t’ {aka ‘long unsigned int’} [-Werror=sign-compare]
  333 |   for (int i = 0; i < proc->prev->size; i++)
      |                     ^
src/utils/proc_pids/proc_pids.c:340:21: error: comparison of integer expressions of different signedness: ‘int’ and ‘size_t’ {aka ‘long unsigned int’} [-Werror=sign-compare]
  340 |   for (int i = 0; i < proc->curr->size; i++)
      |                     ^
cc1: all warnings being treated as errors
*** src/utils/mount/mount.c ***
*** src/utils/config_cores/config_cores.c ***

[eero-t]

If one uses -Wpendantic option:

$ for i in $(find src/ -mindepth 3 -name '*.c' | grep -v -e /dpdk/ -e format_json.c -e format_kairosdb.c -e _mock.c -e _test.c -e _windows.c); do \
  echo "*** $i ***"; \
  gcc -I. -Isrc -Isrc/daemon -Isrc/libcollectdclient -DHAVE_CONFIG_H -O3 -Werror -Wpedantic -c -o /dev/null $i; \
done

there are more warnings, about using void * (data pointers) when code requires function pointers:

*** src/utils/cmds/listval.c ***
*** src/utils/cmds/putnotif.c ***
*** src/utils/cmds/putval.c ***
*** src/utils/cmds/putmetric.c ***
*** src/utils/cmds/flush.c ***
*** src/utils/cmds/parse_option.c ***
*** src/utils/cmds/getthreshold.c ***
*** src/utils/cmds/getval.c ***
*** src/utils/cmds/cmds.c ***
*** src/utils/curl_stats/curl_stats.c ***
*** src/utils/resource_metrics/resource_metrics.c ***
src/utils/resource_metrics/resource_metrics.c: In function ‘lookup_resource’:
src/utils/resource_metrics/resource_metrics.c:43:18: error: ISO C forbids conversion of function pointer to object pointer type [-Werror=pedantic]
   43 |                  (void *)resource_metrics_compare);
      |                  ^
src/utils/resource_metrics/resource_metrics.c:43:18: error: ISO C forbids passing argument 5 of ‘bsearch’ between function pointer and ‘void *’ [-Werror=pedantic]
   43 |                  (void *)resource_metrics_compare);
      |                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/stdlib.h:846,
                 from src/daemon/collectd.h:50,
                 from src/daemon/plugin.h:32,
                 from src/utils/resource_metrics/resource_metrics.c:27:
/usr/include/bits/stdlib-bsearch.h:21:24: note: expected ‘__compar_fn_t’ {aka ‘int (*)(const void *, const void *)’} but argument is of type ‘void *’
   21 |          __compar_fn_t __compar)
      |          ~~~~~~~~~~~~~~^~~~~~~~
src/utils/resource_metrics/resource_metrics.c: In function ‘insert_resource’:
src/utils/resource_metrics/resource_metrics.c:64:9: error: ISO C forbids conversion of function pointer to object pointer type [-Werror=pedantic]
   64 |         (void *)resource_metrics_compare);
      |         ^
src/utils/resource_metrics/resource_metrics.c:64:9: error: ISO C forbids passing argument 4 of ‘qsort’ between function pointer and ‘void *’ [-Werror=pedantic]
   64 |         (void *)resource_metrics_compare);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/stdlib.h:852:34: note: expected ‘__compar_fn_t’ {aka ‘int (*)(const void *, const void *)’} but argument is of type ‘void *’
  852 |                    __compar_fn_t __compar) __nonnull ((1, 4));
      |                    ~~~~~~~~~~~~~~^~~~~~~~
src/utils/resource_metrics/resource_metrics.c: In function ‘lookup_family’:
src/utils/resource_metrics/resource_metrics.c:94:15: error: ISO C forbids conversion of function pointer to object pointer type [-Werror=pedantic]
   94 |               (void *)compare_family_by_name);
      |               ^
src/utils/resource_metrics/resource_metrics.c:94:15: error: ISO C forbids passing argument 5 of ‘bsearch’ between function pointer and ‘void *’ [-Werror=pedantic]
   94 |               (void *)compare_family_by_name);
      |               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/bits/stdlib-bsearch.h:21:24: note: expected ‘__compar_fn_t’ {aka ‘int (*)(const void *, const void *)’} but argument is of type ‘void *’
   21 |          __compar_fn_t __compar)
      |          ~~~~~~~~~~~~~~^~~~~~~~
src/utils/resource_metrics/resource_metrics.c: In function ‘insert_family’:
src/utils/resource_metrics/resource_metrics.c:125:9: error: ISO C forbids conversion of function pointer to object pointer type [-Werror=pedantic]
  125 |         (void *)compare_family_by_name);
      |         ^
src/utils/resource_metrics/resource_metrics.c:125:9: error: ISO C forbids passing argument 4 of ‘qsort’ between function pointer and ‘void *’ [-Werror=pedantic]
  125 |         (void *)compare_family_by_name);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/stdlib.h:852:34: note: expected ‘__compar_fn_t’ {aka ‘int (*)(const void *, const void *)’} but argument is of type ‘void *’
  852 |                    __compar_fn_t __compar) __nonnull ((1, 4));
      |                    ~~~~~~~~~~~~~~^~~~~~~~
src/utils/resource_metrics/resource_metrics.c: In function ‘metric_exists’:
src/utils/resource_metrics/resource_metrics.c:164:55: error: ISO C forbids conversion of function pointer to object pointer type [-Werror=pedantic]
  164 |                             sizeof(*fam->metric.ptr), (void *)compare_metrics);
      |                                                       ^
src/utils/resource_metrics/resource_metrics.c:164:55: error: ISO C forbids passing argument 5 of ‘bsearch’ between function pointer and ‘void *’ [-Werror=pedantic]
  164 |                             sizeof(*fam->metric.ptr), (void *)compare_metrics);
      |                                                       ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/bits/stdlib-bsearch.h:21:24: note: expected ‘__compar_fn_t’ {aka ‘int (*)(const void *, const void *)’} but argument is of type ‘void *’
   21 |          __compar_fn_t __compar)
      |          ~~~~~~~~~~~~~~^~~~~~~~
src/utils/resource_metrics/resource_metrics.c: In function ‘insert_metrics’:
src/utils/resource_metrics/resource_metrics.c:194:11: error: ISO C forbids conversion of function pointer to object pointer type [-Werror=pedantic]
  194 |           (void *)compare_metrics);
      |           ^
src/utils/resource_metrics/resource_metrics.c:194:11: error: ISO C forbids passing argument 4 of ‘qsort’ between function pointer and ‘void *’ [-Werror=pedantic]
  194 |           (void *)compare_metrics);
      |           ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/stdlib.h:852:34: note: expected ‘__compar_fn_t’ {aka ‘int (*)(const void *, const void *)’} but argument is of type ‘void *’
  852 |                    __compar_fn_t __compar) __nonnull ((1, 4));
      |                    ~~~~~~~~~~~~~~^~~~~~~~
cc1: all warnings being treated as errors
*** src/utils/value_list/value_list.c ***
*** src/utils/format_json/open_telemetry.c ***
*** src/utils/ignorelist/ignorelist.c ***
*** src/utils/crc32/crc32.c ***
*** src/utils/format_influxdb/format_influxdb.c ***
*** src/utils/gce/gce.c ***
*** src/utils/avltree/avltree.c ***
*** src/utils/oauth/oauth.c ***
*** src/utils/taskstats/taskstats.c ***
*** src/utils/utf8/utf8.c ***
*** src/utils/ovs/ovs.c ***
*** src/utils/heap/heap.c ***
*** src/utils/format_graphite/format_graphite.c ***
*** src/utils/rrdcreate/rrdcreate.c ***
*** src/utils/match/match.c ***
*** src/utils/tail/tail.c ***
*** src/utils/strbuf/strbuf.c ***
*** src/utils/lookup/vl_lookup.c ***
*** src/utils/message_parser/message_parser.c ***
*** src/utils/dmi/dmi.c ***
*** src/utils/dns/dns.c ***
*** src/utils/db_query/db_query.c ***
*** src/utils/format_stackdriver/format_stackdriver.c ***
src/utils/format_stackdriver/format_stackdriver.c: In function ‘sd_output_create’:
src/utils/format_stackdriver/format_stackdriver.c:495:30: error: ISO C forbids conversion of function pointer to object pointer type [-Werror=pedantic]
  495 |   out->staged = c_avl_create((void *)strcmp);
      |                              ^
src/utils/format_stackdriver/format_stackdriver.c:495:30: error: ISO C forbids passing argument 1 of ‘c_avl_create’ between function pointer and ‘void *’ [-Werror=pedantic]
  495 |   out->staged = c_avl_create((void *)strcmp);
      |                              ^~~~~~~~~~~~~~
In file included from src/utils/format_stackdriver/format_stackdriver.c:28:
src/utils/avltree/avltree.h:54:34: note: expected ‘int (*)(const void *, const void *)’ but argument is of type ‘void *’
   54 | c_avl_tree_t *c_avl_create(int (*compare)(const void *, const void *));
      |                            ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/utils/format_stackdriver/format_stackdriver.c:501:42: error: ISO C forbids conversion of function pointer to object pointer type [-Werror=pedantic]
  501 |   out->metric_descriptors = c_avl_create((void *)strcmp);
      |                                          ^
src/utils/format_stackdriver/format_stackdriver.c:501:42: error: ISO C forbids passing argument 1 of ‘c_avl_create’ between function pointer and ‘void *’ [-Werror=pedantic]
  501 |   out->metric_descriptors = c_avl_create((void *)strcmp);
      |                                          ^~~~~~~~~~~~~~
src/utils/avltree/avltree.h:54:34: note: expected ‘int (*)(const void *, const void *)’ but argument is of type ‘void *’
   54 | c_avl_tree_t *c_avl_create(int (*compare)(const void *, const void *));
      |                            ~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
*** src/utils/metadata/meta_data.c ***
*** src/utils/common/common.c ***
*** src/utils/latency/latency.c ***
*** src/utils/latency/latency_config.c ***
*** src/utils/proc_pids/proc_pids.c ***
*** src/utils/mount/mount.c ***
*** src/utils/config_cores/config_cores.c ***

[eero-t]

Above -Wpedantic output is based on current #4243. I'll add fixes to those cast warnings to it later.

[eero-t]

Additional fixes for warnings listed here are in #4262 and #4264.