Fix GCC warning in msc_headers_to_buffer():

In file included from /usr/include/stdio.h:970,
                 from modsecurity.h:18,
                 from msc_util.c:15:
In function 'sprintf',
    inlined from 'msc_headers_to_buffer' at msc_util.c:2331:17:
/usr/include/bits/stdio2.h:30:10: warning: '__sprintf_chk' argument 5 overlaps destination object 'buffer' [-Wrestrict]
   30 |   return __builtin___sprintf_chk (__s, __USE_FORTIFY_LEVEL - 1,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   31 |                                   __glibc_objsize (__s), __fmt,
      |                                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   32 |                                   __va_arg_pack ());
      |                                   ~~~~~~~~~~~~~~~~~
msc_util.c: In function 'msc_headers_to_buffer':
msc_util.c:2306:64: note: destination object referenced by 'restrict'-qualified argument 1 was declared here
 2306 | int msc_headers_to_buffer(const apr_array_header_t *arr, char *buffer,
      |                                                          ~~~~~~^~~~~~

Author: notroj

apache2/msc_util.c

@@ -2310,9 +2310,11 @@ int msc_headers_to_buffer(const apr_array_header_t *arr, char *buffer,
     int write_to_buffer = 0;
     int i = 0;
     const apr_table_entry_t *te = NULL;
+    char *ptr = NULL;
 
     if (buffer != NULL && buffer_length > 0) {
         write_to_buffer = 1;
+        ptr = buffer;
     }
 
     te = (apr_table_entry_t *)arr->elts;
@@ -2328,7 +2330,9 @@ int msc_headers_to_buffer(const apr_array_header_t *arr, char *buffer,
                     goto not_enough_memory;
                 }
 
-                sprintf(buffer, "%s%s: %s\n", buffer, key, value);
+                assert(ptr && ptr < buffer + buffer_length);
+                sprintf(ptr, "%s: %s\n", key, value);
+                ptr = buffer + headers_length; /* for the next entry. */
             }
     }