Hi,
I followed the link '
https://github.com/golang/go/wiki/cgo#function-variables' and made the
following changes:
*1)main.go*
package main
//#cgo CFLAGS: -I./syslog-ng-3.6.2/
//#cgo LDFLAGS: syslog-node.so
//#cgo LDFLAGS: -L/usr/local/lib/ -lsyslog-ng
//#cgo LDFLAGS: -L/usr/local/lib/syslog-ng -ldbparser
//#cgo CFLAGS: -I.
//void callOnMeGo_cgo(char *key, char *value, size_t value_len); <<<<<
// #include "syslog-node1.h"
//#include <stdlib.h>
import "C"
//export CallBack
func CallBack(key *C.char, value *C.char, value_len C.size_t){
if remap, ok := field_mappings[C.GoString(key)]; ok {
fmt.Println(key, remap)//Need to check how field mappings work
}
}
func ReloadPatternDB(opts Y){
x := C.CString(opts.x)
C.reload_pattern_db(x,
(C.key_value_cb)(unsafe.Pointer(C.callOnMeGo_cgo)));
}
2)Created a file 'cfuncs.go'
*====================*
package main
/*
#include <stdio.h>
// The gateway function
void callOnMeGo_cgo(char *key, char *value, size_t value_len)
{
printf("C.callOnMeGo_cgo(): called");
return CallBack(key, value, value_len);
}
*/
import "C"
*3)Following is my C header file:*
#ifndef _TEST_H_
#define _TEST_H_
#include <stdlib.h>
typedef void (*key_value_cb)(const char* key, const char* value, size_t
value_len);
int initialize_engine(const char* filename, const char* module_path,
key_value_cb cb);
int reload_pattern_db(const char* filename, key_value_cb cb);
void match(const char* pattern, size_t pattern_len, const char* program,
size_t program_len);
#endif
*4)My make file:============*
.PHONY: all clean
all: main
main: syslog-node.so main.go syslog-node1.h
go build -v -x main.go
syslog-node.so: syslog-node.c syslog-node1.h cfuncs.go
gcc -L/usr/local/lib -lsyslog-ng -o syslog-node.so
-L/usr/local/lib/syslog-ng -ldbparser -c `pkg-config --libs --cflags
glib-2.0` -I/usr/local/include/syslog-ng/ -I./syslog-ng-3.6.2/
-I/usr/local/include/eventlog/ -I. syslog-node.c
clean:
rm main
rm syslog-node.so
*5) When I run the make command, I get the following error *
v$ make
gcc -L/usr/local/lib -lsyslog-ng -o syslog-node.so
-L/usr/local/lib/syslog-ng -ldbparser -c `pkg-config --libs --cflags
glib-2.0` -I/usr/local/include/syslog-ng/ -I./syslog-ng-3.6.2/
-I/usr/local/include/eventlog/ -I. syslog-node.c
go build -v -x main.go
WORK=/tmp/go-build729657300
command-line-arguments
mkdir -p $WORK/b001/
cd /home/nitish/Documents/goworkspace/src/Syslogng/node-syslog-ng-dev
CGO_LDFLAGS='"-g" "-O2" "syslog-node.so" "-L/usr/local/lib/" "-lsyslog-ng"
"-L/usr/local/lib/syslog-ng" "-ldbparser"'
/usr/local/go/pkg/tool/linux_amd64/cgo -objdir $WORK/b001/ -importpath
command-line-arguments -- -I $WORK/b001/ -g -O2
-I/home/nitish/Documents/goworkspace/src/Syslogng/node-syslog-ng-dev/syslog-ng-3.6.2
-I/home/nitish/Documents/goworkspace/src/Syslogng/node-syslog-ng-dev
./main.go
cd $WORK
gcc -fno-caret-diagnostics -c -x c - || true
gcc -Qunused-arguments -c -x c - || true
gcc -fdebug-prefix-map=a=b -c -x c - || true
gcc -gno-record-gcc-switches -c -x c - || true
cd $WORK/b001
TERM='dumb' gcc -I
/home/nitish/Documents/goworkspace/src/Syslogng/node-syslog-ng-dev -fPIC
-m64 -pthread -fmessage-length=0
-fdebug-prefix-map=$WORK/b001=/tmp/go-build -gno-record-gcc-switches -I ./
-g -O2
-I/home/nitish/Documents/goworkspace/src/Syslogng/node-syslog-ng-dev/syslog-ng-3.6.2
-I/home/nitish/Documents/goworkspace/src/Syslogng/node-syslog-ng-dev -o
./_x001.o -c _cgo_export.c
TERM='dumb' gcc -I
/home/nitish/Documents/goworkspace/src/Syslogng/node-syslog-ng-dev -fPIC
-m64 -pthread -fmessage-length=0
-fdebug-prefix-map=$WORK/b001=/tmp/go-build -gno-record-gcc-switches -I ./
-g -O2
-I/home/nitish/Documents/goworkspace/src/Syslogng/node-syslog-ng-dev/syslog-ng-3.6.2
-I/home/nitish/Documents/goworkspace/src/Syslogng/node-syslog-ng-dev -o
./_x002.o -c main.cgo2.c
TERM='dumb' gcc -I
/home/nitish/Documents/goworkspace/src/Syslogng/node-syslog-ng-dev -fPIC
-m64 -pthread -fmessage-length=0
-fdebug-prefix-map=$WORK/b001=/tmp/go-build -gno-record-gcc-switches -I ./
-g -O2
-I/home/nitish/Documents/goworkspace/src/Syslogng/node-syslog-ng-dev/syslog-ng-3.6.2
-I/home/nitish/Documents/goworkspace/src/Syslogng/node-syslog-ng-dev -o
./_cgo_main.o -c _cgo_main.c
cd /home/nitish/Documents/goworkspace/src/Syslogng/node-syslog-ng-dev
TERM='dumb' gcc -I . -fPIC -m64 -pthread -fmessage-length=0
-fdebug-prefix-map=$WORK/b001=/tmp/go-build -gno-record-gcc-switches -o
$WORK/b001/_cgo_.o $WORK/b001/_cgo_main.o $WORK/b001/_x001.o
$WORK/b001/_x002.o -g -O2 syslog-node.so -L/usr/local/lib/ -lsyslog-ng
-L/usr/local/lib/syslog-ng -ldbparser
# command-line-arguments
/tmp/go-build729657300/b001/_cgo_main.o:/tmp/go-build/cgo-generated-wrappers:2:
undefined reference to `callOnMeGo_cgo'
collect2: error: ld returned 1 exit status
makefile:6: recipe for target 'main' failed
make: *** [main] Error 2
Can someone please point me the what am I missing in my make file or
something else in my code base that will resolve this error ?
Thanks
On Wed, Apr 24, 2019 at 2:35 PM Jan Mercl <0xj...@gmail.com> wrote:
> On Wed, Apr 24, 2019 at 10:47 AM Nitish Saboo <nitish.sabo...@gmail.com>
> wrote:
>
> > ./main.go:80:32: cannot use key (type *_Ctype_char) as type string in
> map index
>
> func CallBack(ckey *C.char, value *C.char, value_len C.size_t){
> key := C.GoString(ckey)
> if remap, ok := field_mappings[key]; ok {
> fmt.Println(key, remap)
> }
> }
>
>
> > ./main.go:91:21: cannot use CallBack (type func(*_Ctype_char,
> *_Ctype_char, _Ctype_ulong)) as type *[0]byte in argument to
> _Cfunc_reload_pattern_db
> > ./main.go:143:21: cannot use CallBack (type func(*_Ctype_char,
> *_Ctype_char, _Ctype_ulong)) as type *[0]byte in argument to
>
> See https://github.com/golang/go/wiki/cgo#function-variables:
>
> "Because of the pointer passing rules Go code can not pass a
> function value directly to C. "
>
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