Prohibit verbose strcat

Using strcat directly is more readable than passing strlen
of the copied string to strncat.

cfg.mk

@@ -1031,6 +1031,12 @@ sc_prohibit_not_strneq:
 	halt='Use STREQ instead of !STRNEQ'	\
 	  $(_sc_search_regexp)
 
+sc_prohibit_verbose_strcat:
+	@prohibit='strncat\([^,]*,\s+([^,]*),\s+strlen\(\1\)\)'     \
+	in_vc_files='\.[ch]$$'                                      \
+	halt='Use strcat(a, b) instead of strncat(a, b, strlen(b))' \
+	  $(_sc_search_regexp)
+
 # We don't use this feature of maint.mk.
 prev_version_file = /dev/null
 

src/storage/storage_backend_logical.c

@@ -123,11 +123,11 @@ virStorageBackendLogicalParseVolExtents(virStorageVolDefPtr vol,
     /* Allocate space for 'nextents' regex_unit strings plus a comma for each */
     if (VIR_ALLOC_N(regex, nextents * (strlen(regex_unit) + 1) + 1) < 0)
         goto cleanup;
-    strncat(regex, regex_unit, strlen(regex_unit));
+    strcat(regex, regex_unit);
     for (i = 1; i < nextents; i++) {
         /* "," is the separator of "devices" field */
         strcat(regex, ",");
-        strncat(regex, regex_unit, strlen(regex_unit));
+        strcat(regex, regex_unit);
     }
 
     if (VIR_ALLOC(reg) < 0)