A signal handler that calls for example waitpid has to save errno before and

restore it afterwards.

Cherry-picked from: 70b4927d847f52c865e0c6c91323eeb3295a99eb

Signed-off-by: Luke Dashjr <luke-jr+git@utopios.org>
(cherry picked from commit c80147f221)

tdeioslave/imap4/imap4.cc

@@ -71,6 +71,7 @@ imap://server/folder/
 #include <signal.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <errno.h>
 
 #ifdef HAVE_LIBSASL2
 extern "C" {
@@ -147,6 +148,10 @@ kdemain (int argc, char **argv)
 void
 sigchld_handler (int signo)
 {
+  // A signal handler that calls for example waitpid has to save errno
+  // before and restore it afterwards.
+  // (cf. https://www.securecoding.cert.org/confluence/display/cplusplus/ERR32-CPP.+Do+not+rely+on+indeterminate+values+of+errno)
+  const int save_errno = errno;
   int pid, status;
 
   while (signo == SIGCHLD)
@@ -158,9 +163,11 @@ sigchld_handler (int signo)
       // the signal occurred ( BSD handles it different, but it should do
       // no harm ).
       signal (SIGCHLD, sigchld_handler);
-      return;
+      break;
     }
   }
+
+  errno = save_errno;
 }
 
 IMAP4Protocol::IMAP4Protocol (const TQCString & pool, const TQCString & app, bool isSSL):TCPSlaveBase ((isSSL ? 993 : 143),