Index: openacs-4/packages/xotcl-core/www/show-class-graph.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/xotcl-core/www/show-class-graph.tcl,v
diff -u -r1.12.2.4 -r1.12.2.5
--- openacs-4/packages/xotcl-core/www/show-class-graph.tcl	2 Aug 2021 21:16:33 -0000	1.12.2.4
+++ openacs-4/packages/xotcl-core/www/show-class-graph.tcl	29 Nov 2021 13:20:11 -0000	1.12.2.5
@@ -15,24 +15,30 @@
 set dot_code [::xo::dotcode -dpi $dpi \
                   -with_children $with_children -documented_methods $documented_only \
                   $classes]
-set dot ""
-catch {set dot [::util::which dot]}
-# final resort for cases, where ::util::which is not available
-if {$dot eq "" && [file executable /usr/bin/dot]} {set dot /usr/bin/dot}
-if {$dot eq ""} {ns_return 404 plain/text "dot not found"; ad_script_abort}
+set dot [::util::which dot]
 
-set tmpnam [ad_tmpnam]
-set tmpfile $tmpnam.$format
+if {$dot eq ""} {
+  ns_return 404 plain/text "dot not found"
+  ad_script_abort
+}
 
-#ns_log notice "png $tmpnam dot $tmpnam.dot"
-set f [open "|$dot  -T$format -o $tmpfile" w]; puts $f $dot_code; close $f
-ns_returnfile 200 [ns_guesstype $tmpfile] $tmpfile
-file delete -- $tmpfile
+set stem [ad_tmpnam]
+set dotfile $stem.dot
+set outfile $stem.$format
 
-#set f [open $tmpnam.dot w]; puts $f $dot_code; close $f
-#file delete -- $tmpnam.dot
+try {
+  set f [open $dotfile w]; puts $f $dot_code; close $f
+  exec $dot -T$format -o $outfile $dotfile
+} on error {errorMsg} {
+  ns_log warning "show-class-graph: dot returned $errorMsg"
+  ad_return_error "dot error" $errorMsg
+} on ok {result} {
+  ns_returnfile 200 [ns_guesstype $outfile] $outfile
+  file delete -- $outfile
+} finally {
+  file delete -- $dotfile
+}
 
-
 #
 # Local variables:
 #    mode: tcl