亚历山大;
OpenCOBOL 2.0 将具有 FUNCTION-ID 允许诸如
MOVE FUNCTION nextbigthing(args) TO cobol-working-store
但是，在它发布之前，我们“仅限于”CALL、ENTRY、PROGRAM-ID 等。
有关一些低级函数指针相关事物的示例，请查看
http://opencobol.add1tocobol.com/#what-stock-call-library-does-opencobol-offer
其中包括用于设置错误处理程序和退出程序的片段。用眼睛扫描它
- 程序指针
- 入口
- 将 proc-ptr 设置为条目“链接名称”
- 呼叫...使用...返回
需要注意的是，这是一种方法。还有其他的。PROGRAM-ID 子程序等的 ENTRY 行可以是完整的。OpenCOBOL FAQ 的第 5 节充斥着从其他语言和链接库来回传递数据的例程。
另外，查看 libcob/common.h 中的 cob_field。CALL 生成的 C 代码设置参数的 COBOL 字段数组以及实际调用帧，并且可以通过 cob_module 从 C 函数访问这些 COBOL 字段结构。
errorproc.cob
>>SOURCE FORMAT IS FIXED
*****************************************************************
* OpenCOBOL demonstration
* Author: Brian Tiffin
* Date: 26-Jun-2008
* History:
* 03-Jul-2008
* Updated to compile warning free according to standards
* Purpose:
* CBL_ERROR_PROC and CBL_EXIT_PROC call example
* CBL_ERROR_PROC installs or removes run-time error procedures
* CBL_EXIT_PROC installs or removes exit handlers
* Also demonstrates the difference between Run time errors
* and raised exceptions. Divide by zero raises an
* exception, it does not cause a run time error.
* NB:
* Please be advised that this example uses the functional but
* now obsolete ENTRY verb. Compiling with -Wall will display
* a warning. No warning will occur using -std=MF
* Tectonics: cobc -x errorproc.cob
identification division.
program-id. error_exit_proc.
data division.
working-storage section.
* entry point handlers are procedure addresses
01 install-address usage is procedure-pointer.
01 install-flag pic 9 comp-x value 0.
01 status-code pic s9(9) comp-5.
* exit handler address and priority (prio is IGNORED with OC1.1)
01 install-params.
02 exit-addr usage is procedure-pointer.
02 handler-prio pic 999 comp-x.
* indexing variable for back scannning error message strings
01 ind pic s9(9) comp-5.
* work variable to demonstrate raising exception, not RTE
01 val pic 9.
* mocked up error procedure reentrancy control, global level
01 once pic 9 value 0.
88 been-here value 1.
* mocked up non-reentrant value
01 global-value pic 99 value 99.
* LOCAL-STORAGE SECTION comes into play for ERROR_PROCs that
* may themselves cause run-time errors, handling reentry.
local-storage section.
01 reenter-value pic 99 value 11.
* Linkage section for the error message argument passed to proc
* By definition, error messages are 325 alphanumeric
linkage section.
01 err-msg pic x(325).
* example of OpenCOBOL error and exit procedures
procedure division.
* Demonstrate problem installing procedure
* get address of WRONG handler. NOTE: Invalid address
set exit-addr to entry "nogo-proc".
* flag: 0 to install, 1 to remove
call "CBL_EXIT_PROC" using install-flag
install-params
returning status-code
end-call.
* status-code 0 on success, in this case expect error.
if status-code not = 0
display
"Intentional problem installing EXIT PROC"
", Status: " status-code
end-display
end-if.
* Demonstrate install of an exit handler
* get address of exit handler
set exit-addr to entry "exit-proc".
* flag: 0 to install, 1 to remove
call "CBL_EXIT_PROC" using install-flag
install-params
returning status-code
end-call.
* status-code 0 on success.
if status-code not = 0
display
"Problem installing EXIT PROC"
", Status: " status-code
end-display
stop run
end-if.
* Demonstrate installation of an error procedure
* get the procedure entry address
set install-address to entry "err-proc".
* install error procedure. install-flag 0 installs, 1 removes
call "CBL_ERROR_PROC" using install-flag
install-address
returning status-code
end-call.
* status-code is 0 on success.
if status-code not = 0
display "Error installing ERROR PROC" end-display
stop run
end-if.
* example of error that raises exception, not a run-time error
divide 10 by 0 giving val end-divide.
* val will be a junk value, use at own risk
divide 10 by 0 giving val
on size error display "DIVIDE BY ZERO Exception" end-display
end-divide.
* intentional run-time error
call "erroneous" end-call. *> ** Intentional error **
* won't get here. RTS error handler will stop run
display
"procedure division, following run-time error"
end-display.
display
"global-value: " global-value
", reenter-value: " reenter-value
end-display.
exit program.
*****************************************************************
*****************************************************************
* Programmer controlled Exit Procedure:
entry "exit-proc".
display
"**Custom EXIT HANDLER (will pause 3 and 0.5 seconds)**"
end-display.
* sleep for 3 seconds
call "C$SLEEP" using "3" end-call.
* demonstrate nanosleep; argument in billionth's of seconds
* Note: also demonstrates OpenCOBOL's compile time
* string catenation using ampersand;
* 500 million being one half second
call "CBL_OC_NANOSLEEP" using "500" & "000000" end-call.
exit program.
*****************************************************************
* Programmer controlled Error Procedure:
entry "err-proc" using err-msg.
display "**ENTER error procedure**" end-display.
* These lines are to demonstrate local and working storage
display
"global-value: " global-value
", reenter-value: " reenter-value
end-display.
* As reenter-value is local-storage
* the 77 will NOT display on rentry, while the global 66 will
move 66 to global-value.
move 77 to reenter-value.
* Process err-msg.
* Determine Length of error message, looking for null terminator
perform varying ind from 1 by 1
until (err-msg(ind:1) = x"00") or (ind = length of err-msg)
continue
end-perform.
display err-msg(1:ind) end-display.
* demonstrate trapping an error caused in error-proc
if not been-here then
set been-here to true
display "Cause error while inside error-proc" end-display
call "very-erroneous" end-call *> Intentional error
end-if.
* In OpenCOBOL 1.1, the return-code is local and does
* not influence further error handlers
*move 1 to return-code.
move 0 to return-code.
display "**error procedure EXIT**" end-display.
exit program.