I am writing a program that needs a pathname to eventually create a global string. I currently have this pathname hard coded, but would like to use a global variable to replace this. The problem I am having is that my global variable is undefined. I am also using JNI and the error I am getting is:
#
# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00007f65f981ddd0, pid=11660, tid=140075985102592
#
# JRE version: 7.0_21-b02
# Java VM: OpenJDK 64-Bit Server VM (23.7-b01 mixed mode linux-amd64 compressed oops)
# Problematic frame:
# C [libstdc++.so.6+0x9ddd0] std::string::size() const+0x0
#
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# An error report file with more information is saved as:
# /home/cbil/Desktop/SIGH_Project/July_9/src/hs_err_pid11660.log
#
# If you would like to submit a bug report, please include
# instructions on how to reproduce the bug and visit:
# https://bugs.launchpad.net/ubuntu/+source/openjdk-7/
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#
and here is relevant code that is reformatted for simplicity:
file1.cpp
#include <jni.h>
#include "file1.h"
#include <iostream>
#include <fstream>
#include <string.h>
using namespace std;
const char* myPath;
JNIEXPORT jint JNICALL Java_foo_foo(JNIEnv *env, jobject thisobj, jbyteArray passedPath){
/*Some conversion, don't think it is relevant, but it might be*/
jboolean isCopy;
jbyte* path = env->GetByteArrayElements(passedPath,&isCopy);
int length1 = strlen((const char*)path);
char* convertedVar = (char*)malloc(length1+1);
memcpy(convertedVar,path,length1);
convertedVar[length1] = '\0';
convertedVar = (char*)path;
/*End Conversion*/
globalVariable = convertedVar;
... //Some code to use the variable and releases
}
file2.h (This is where I declare the global variable)
#include <vector>
#include <fstream>
#include <string.h>
extern const char* globalVariable;
extern int someNum;
extern int someLength;
class file2{
public:
static std::vector<std::string> getSomeString(int &someNum, int &someLength);
private:
static const std::vector<std::string> anotherVar;
...//some other variables and methods
}
and finally the code that calls getSomeString
file3.cpp
#include "file2.h"
#include <string.h>
#include <vector>
#include <fstream>
using namespace std;
int someNum = 0;
int someLength = 0;
const char* globalVariable;
vector<string> file2::getSomeString(int &someNum, iint &someLength){
vector<string> data;
ifstream infile(globalVariable); //I think the problem is here
string line;
...// some code that goes through the data file specified by the path name
someNum = data.size();
someLength = data[0].size();
return data;
}
const vector<string> file2::anotherVar = getSomeString(someNum,someLength); //variable that uses the getSomeString method
}
I'll say it here again, I am using JNI. I have gotten errors saying the lib.so file I create has undefined variables, I don't know if this is helpful information. Any help would be appreciated. Sorry about the long post, I am quite lost.
char* convertedVar = (char*)malloc(length1+1); memcpy(convertedVar,path,length1); convertedVar[length1] = '\0'; convertedVar = (char*)path;
I'm pretty sure this last line shouldn't be there. You are going through this malloc
/memcpy
dance, then promptly drop this allocated-and-initialized block of memory on the floor, and make convertedVar
point to something else instead.
Further, I'm pretty sure path
pointer will become invalid as soon as the function returns.