const char * Tcl_Concat(argc, argv)
Tcl_Concat is a utility procedure used by several of the Tcl commands. Given a collection of strings, it concatenates them together into a single string, with the original strings separated by spaces. This procedure behaves differently than Tcl_Merge, in that the arguments are simply concatenated: no effort is made to ensure proper list structure. However, in most common usage the arguments will all be proper lists themselves; if this is true, then the result will also have proper list structure.
Tcl_Concat eliminates leading and trailing white space as it copies strings from argv to the result. If an element of argv consists of nothing but white space, then that string is ignored entirely. This white-space removal was added to make the output of the concat command cleaner-looking.
The result string is dynamically allocated using Tcl_Alloc; the caller must eventually release the space by calling Tcl_Free.