Add an entry about the return value of wait/waitpid.

Henning Meier-Geinitz <henning@meier-geinitz.de>

TODO

@@ -1,4 +1,4 @@
-TODO (2002-04-23)
+TODO (2002-05-05)
 
 ******** todo ********
 
@@ -76,6 +76,11 @@ backends
     "../../backend/coolscan-scsidef.h", line 160: warning: initialization
     type mismatch; empty declarations), see sane-devel.
 
+  * Check the return value of wait() and waitpid(). This is important, if
+    the status value is checked for e.g. WIFEXITED after the call of wait()
+    or waitpid(). Both functions may fail if the frontend already did a wait for
+    the children.
+
 doc
 ---
   * Add doxygen documentation for the remaining sanei files:

doc/backend-writing.txt

@@ -1,4 +1,4 @@
-2002-04-22
+2002-05-05
 
 Here are a few rules and tips that should help writing a
 SANE-conformant backend and including it into the SANE package:
@@ -140,6 +140,11 @@ PROGRAMMING
 * Don't use exit() in your backend. You will exit the whole program, not only
   your backend.
 
+* If you use wait() or waitpid() in your backend, check its return value. This
+  is important, if the status value is checked for e.g. WIFEXITED after the
+  call of wait() or waitpid(). Both functions may fail if the frontend already
+  did a wait for the children.
+
 * Please try to avoid compilation warnings. At least with "--disable-warnings"
   there shouldn't be warnings when compiling backends. It's not necessary to
   fix every "unused parameter" warning but take care that no warnings pointing