c++ - System() call returns 255, but executes afterwards -

i running mongoose 3.7 server on qnx system.

i receive http request upgrade firmware. on request, use, system() call in request handler upgrade firmware.

but, strangely, system() returns 255. same call working before mongoose 2.0.

even more strange, command issued through system() call works after returned 255.

i using wexitstatus know error system() returns

any idea why happening?

i found issue..

the issue mongoose call thread issues system() command not wait return status becuase of line:

on mg_start() function, starts server thread, have included line:

mg_start() line no 5159:

(void) signal(sigchld, sig_ign); 

they have done inorder not create zombie process.

ref: http://www.win.tue.nl/~aeb/linux/lk/lk-5.html

but, according qnx documentation,

“setting signal action sig_ign signal that's pending causes pending signal discarded, whether or not blocked. if process sets action sigchld signal sig_ign, behavior unspecified.”

calling sig_ign on sigchld causes parent process ignore status signal child.

when make system() call, blocks sigchld signal shell being launched. according unix documentation:

“blocking sigchld while waiting child terminate prevents application catching signal , obtaining status system()'s child process before system() can status itself.”

but, since mongoose discards signal, not wait signal system() @ all.

it continues serve response without valid return status system().

i commented out line time being. , it’s working.