Add more warnings.

These find an old bug-let in hts_parse_format():
The buffer size is 8, but it includes \0 so the string would have been
truncated, causing the strcmp to fail for "fastq.gz".

Curiously gcc 10 and 11 spot this, but not gcc 12 or 13, nor clang.

.cirrus.yml

@@ -141,7 +141,7 @@ rocky_task:
     LC_ALL: C
     CIRRUS_CLONE_DEPTH: 1
     USE_CONFIG: yes
-    CFLAGS: -std=gnu90 -Wformat -Wformat=2
+    CFLAGS: -g -O3 -std=gnu90 -Wformat -Wformat=2 -Wextra -Wno-sign-compare -Wno-unused-parameter -Wno-missing-field-initializers -Wno-empty-body
 
   # NB: we could consider building a docker image with these
   # preinstalled and specifying that instead, to speed up testing.

hts.c

@@ -1322,7 +1322,7 @@ int hts_parse_opt_list(htsFormat *fmt, const char *str) {
  *        -1 on failure.
  */
 int hts_parse_format(htsFormat *format, const char *str) {
-    char fmt[8];
+    char fmt[9];
     const char *cp = scan_keyword(str, ',', fmt, sizeof fmt);
 
     format->version.minor = 0; // unknown

test/test-bcf-sr.c

@@ -179,6 +179,7 @@ int main(int argc, char *argv[])
                 break;
             case 'h':
                 usage(EXIT_SUCCESS);
+                // fall-through
             default: usage(EXIT_FAILURE);
         }
     }