All subroutines must return a C long integer. The return value is available to the ESL program through the built-in function errorlevel. This returned quantity should be zero if the C subroutine encountered no errors, or non-zero if an error was generated. To determine if an error was generated during the subroutine call, the errorlevel function can be interrogated by the calling program after it has returned, as follows:

 

subroutine SubroutineCall(integer:Param1)

library "DLLNAME"

 

call SubroutineCall(Integer_IV)

 

if (errorlevel != 0) then

send "Error in SubroutineCall\n" to errorlog 

end if