String parameters

Question

I'm trying to use swig to interact with C ++, and I'm having problems using the std::string& parameter. This is on Fedora 19 with golang 1.1-2, swig 2.0.10-1 and gcc 4.8.1-1.

I do not know C ++. I know C, and hoped it would be a wing. Anyway, _swig_wrap_pinput ends with a null pointer.

What am I missing?

Here is my test case:

st.i

 %module st %{ #include <string> extern void pinput(std::string& pstring); %} %include <std_string.i> #include <string> void pinput(std::string& pstring); 

st.cxx

 #include <stddef.h> #include <stdio.h> #include <stdlib.h> #include <string> #include <iostream> void pinput(std::string& pstring) { std::cout<<pstring; } 

stmain.go

 package main import ( "st" ) func main() { myLit:="This is a test." st.Pinput(&myLit) } 

Makefile

 SWIGOBJS = st_gc.c st_wrap.cxx st.go all: st.so st.a $(SWIGOBJS): st.i swig -go -c++ -intgosize 64 st.i st.o: st.cxx g++ -c -fpic -g -o st.o st.cxx st_wrap.o: st_wrap.cxx g++ -c -fpic -g -o st_wrap.o st_wrap.cxx st.so: st_wrap.o st.o g++ -shared st_wrap.o st.o -o st.so st_gc.6: st_gc.c /usr/lib64/golang/pkg/tool/linux_amd64/6c -I /usr/lib64/golang/pkg/linux_amd64 st_gc.c st.6: st.go /usr/lib64/golang/pkg/tool/linux_amd64/6g st.go st.a: st.6 st_gc.6 go tool pack grc st.a st.6 st_gc.6 test: stmain stmain: stmain.6 /usr/lib64/golang/pkg/tool/linux_amd64/6l stmain.6 stmain.6: stmain.go /usr/lib64/golang/pkg/tool/linux_amd64/6g stmain.go 

Answer 1

Since the question was originally asked, both the Go and SWIG updates were updated. I will post a solution that worked for me (Go 1.3.3, SWIG 3.0.2). As you can see, the difference with the original message is minimal.

The most recommended approach is to use go build. He currently knows the * .swig and * .swigcxx files and starts both SWIG and GCC / g ++ automatically based on the information found in the swig interface file.

stmain.go

 package main import ( "st" // This will be created by SWIG ) func main() { myLit:="This is a test." st.Pinput(myLit) } 

th /st.h

 ifndef ST_H #define ST_H #include <stddef.h> #include <stdio.h> #include <stdlib.h> #include <string> #include <iostream> void pinput(const std::string& pstring); #endif 

th /st.cpp

 #include <stddef.h> #include <stdio.h> #include <stdlib.h> #include <string> #include <iostream> void pinput(const std::string& pstring) { std::cout << pstring; std::cout << std::endl; // Without endl the stdout doesn't get flushed for me -> no output } 

th /st.go

 package st // Without any Go file in the directory the go build will fail 

th /st.swigcxx

 %module st %include "std_string.i" %include "st.h" %{ extern void pinput(const std::string& pstring); %} void pinput(const std::string& pstring); 

To create and run

 // Quick'n'dirty version # go build stmain.go # ./stmain This is a test. # 

Alternatively, you can create the same sources manually using 6g / c / l / swig / gotool, for example, my simplified version:

Makefile:

 all: make -C st /usr/local/go/pkg/tool/linux_amd64/6g -I st stmain.go /usr/local/go/pkg/tool/linux_amd64/6l -o stmain -extldflags -lstdc++ -L st stmain.6 clean: rm -f *.6 6.out make clean -C st test: stmain 

th / Makefile:

 all: clean swig -go -intgosize 64 -c++ -soname st.so st.swigcxx g++ -c st.cpp -o st.o g++ -c st_wrap.cxx -o st_wrap.o /usr/local/go/pkg/tool/linux_amd64/6c -I /usr/local/go/pkg/linux_amd64/ -D _64BIT st_gc.c /usr/local/go/pkg/tool/linux_amd64/6g st.go go tool pack grc st.a st.6 st_gc.6 st.o st_wrap.o clean: rm -f *.6 rm -f *.a rm -f *.so rm -f *.cxx rm -f *.c rm -f *.o