How to compile COBOL program into shared library

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This sample describe how compile mixed COBOL and C program into a single shared library, and used by C program.

1. HELLOCBL.cbl: provide a COBOL function

2. HELLOCPP.c : provide a C function

3. mypgm.cc: the major executable file

1 and 2 is compiled into a shared library libmylib.so

COBOL-IT compiler is used.

HELLOCBL.cbl

       IDENTIFICATION   DIVISION.       PROGRAM-ID.      HELLOCBL.       ENVIRONMENT      DIVISION.       INPUT-OUTPUT     SECTION.       DATA DIVISION.       WORKING-STORAGE SECTION.         01  ARG        PIC X(50) VALUE SPACES.       LINKAGE SECTION.         01  PARM-SIZE  PIC S9(8) COMP-5.         01  PARM-DATA  PIC X(256).       PROCEDURE DIVISION USING PARM-SIZE PARM-DATA.           DISPLAY "HELLOCBL PARM-SIZE=[" PARM-SIZE "]".           DISPLAY "HELLOCBL PARM-DATA=[" PARM-DATA(1:PARM-SIZE) "]".           MOVE 2 TO RETURN-CODE.           GOBACK.      *    STOP RUN.

HELLOCPP.c

//extern "C"int HELLOCPP(int i, char * buffer) {    printf("HELLOCPP PARM-SIZE=[%d]\n", i);    printf("HELLOCPP PARM-DATA=[%s]\n", buffer);    return 1;}

mypgm.cpp

#include <string.h>#include <dlfcn.h>#include <libcob.h>typedef int (* func_t)(int, char *);void * loadHandle(const char * library) {    void * handle = dlopen(library, RTLD_LAZY | RTLD_GLOBAL);    char * errmsg = dlerror();    if (errmsg != NULL) {        printf("Cannot load shared library: [%s]: [%s]", library, errmsg);        return NULL;    }    if (handle == NULL) {        printf("Cannot load shared library: [%s]", library);        return NULL;    }    return handle;}func_t loadFunction(void * handle, const char * name) {    func_t func = (func_t) dlsym(handle, name);    if (func == 0) {        printf("Cannot get dlsym: [%s]", name);        return NULL;    }    return func;}void callcppfunc(void * handle) {    func_t funcpp = loadFunction(handle, "HELLOCPP");    if (funcpp != NULL) {        int ret = funcpp(5, "1234567890");        printf("HELLOCPP return %d\n", ret);    }}void callcblfunc(int argc, char * argv[]) {    cit_runtime_t * rtd = cob_get_rtd();    cob_init(rtd, argc, argv);    int size = 5;    char buffer[] = { "1234567890" };    void *  cobargv[3];    cobargv[0] = (void *)&size;    cobargv[1] = (void *)buffer;    cobargv[2] = NULL;    int ret = cobcall("HELLOCBL", 2, cobargv);    printf("HELLOCBL return %d\n", ret);    cob_rtd_tidy(rtd);}int main(int argc, char *argv[]){    const char * library = "libmylib.so";    void * handle = loadHandle(library);    if (handle != NULL) {        callcppfunc(handle);        callcblfunc(argc, argv);    }    return 0;}

makefile

PROGRAM=mypgmLIBRARY=libmylib.soall: $(PROGRAM) $(LIBRARY)mypgm: mypgm.cpp        g++ $< -g -o $@ -I$(COBDIR)/include -L$(COBDIR)/lib -lcobit -ldl$(LIBRARY): HELLOCBL.cbl HELLOCPP.c        cobc -fno-C-cmd-line -Wlinkage -b -g -v -fixed $^ -o $(@F) -std=mf -fmf-gnt -constant "UPPER-CALL=1"clean:        -rm -rf c *.lst *.lis *.int *.idy $(LIBRARY) $(PROGRAM)

Execution

$ make$ ./mypgm HELLOCPP PARM-SIZE=[5]HELLOCPP PARM-DATA=[1234567890]HELLOCPP return 1HELLOCBL PARM-SIZE=[+0000000005]HELLOCBL PARM-DATA=[12345]HELLOCBL return 2

the end

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