make utils::errorurl() point to generic page with error code 0

src/utils.cpp

@@ -281,7 +281,11 @@ void utils::fmtargs_print(FILE *fp, fmt::string_view format, fmt::format_args ar
 
 std::string utils::errorurl(int errorcode)
 {
+  if (errorcode == 0)
+    return "\nFor more information see https://docs.lammps.org/Errors_details.html";
+  else if (errorcode > 0)
     return fmt::format("\nFor more information see https://docs.lammps.org/err{:04d}", errorcode);
+  else return ""; // negative numbers are reserved for future use pointing to a different URL
 }
 
 void utils::flush_buffers(LAMMPS *lmp)

src/utils.h

@@ -173,11 +173,12 @@ output are compressed to a single blank by calling :cpp:func:`strcompress()`
    *
    * The LAMMPS manual contains detailed explanations for errors and
    * warnings where a simple error message may not be sufficient.  These can
-   * be reached through URLs with a numeric code.  This function creates the
+   * be reached through URLs with a numeric code > 0.  This function creates the
    * corresponding text to be included into the error message that redirects
-   * the user to that URL.
+   * the user to that URL.  Using an error code of 0 returns a message
+   * pointing to a URL discussing error messages in general.
    *
-   *  \param errorcode   number pointing to a paragraph in the manual */
+   *  \param errorcode   non-negative number pointing to a paragraph in the manual */
 
   std::string errorurl(int errorcode);