backend/ipp.c: Fix printing jobs with long names on older IPP printers

On older printers (ones which don't support IPP operation Create-Job)
we concatenate job number and title into one string, which we use as
IPP attribute job-name. If the original title was almost 255 chars,
the joining the strings will overflow maximal required length
for this attribute, and Validate-Job fails.

We could check whether the string is longer than 255 and cut it,
but I chose to shrink the buffer to 256, since we already use snprintf()
which will cut the string and put null terminator for us.

Fixes #644

CHANGES.md

@@ -4,6 +4,7 @@ CHANGES - OpenPrinting CUPS 2.4.8 - TBA
 Changes in CUPS v2.4.8 (TBA)
 ----------------------------
 
+- Fixed printing of jobs with job name longer than 255 chars on older printers (Issue #644)
 - Really backport fix for Issue #742
 - Raised `cups_enum_dests()` timeout for listing available IPP printers (Issue #751)
 - Fixed memory leak when unloading a job (Issue #813)

backend/ipp.c

@@ -219,7 +219,7 @@ main(int  argc,				/* I - Number of command-line args */
   off_t		compatsize = 0;		/* Size of compatibility file */
   int		port;			/* Port number (not used) */
   char		uri[HTTP_MAX_URI];	/* Updated URI without user/pass */
-  char		print_job_name[1024];	/* Update job-name for Print-Job */
+  char		print_job_name[256];	/* Update job-name for Print-Job */
   http_status_t	http_status;		/* Status of HTTP request */
   ipp_status_t	ipp_status;		/* Status of IPP request */
   http_t	*http;			/* HTTP connection */
@@ -1484,6 +1484,10 @@ main(int  argc,				/* I - Number of command-line args */
   }
   else
   {
+   /*
+    * TODO: make this compatible with UTF-8 - possible UTF-8 truncation here..
+    */
+
     snprintf(print_job_name, sizeof(print_job_name), "%s - %s", argv[1],
              argv[3]);
     monitor.job_name = print_job_name;