Trying to use emu_instruction in libemu gives forward declaration error

Question

I'm writing a code obfuscation tool as a part of my master thesis and I have run in to some problems.

I use libemu for emulating x86 instructions and I would like to read an input file containing hexcode and store the instructions in a vector. In libemu the instructions are represented by the struct emu_instruction and I would like to use this struct in my program also since libemu also provides a parser. This is how I would like to use it:

emulator.cpp

std::vector<struct emu_instruction*> Emulator::getInstructionVector()
{
    std::vector<struct emu_instruction*> v;
    //e is my struct emu*
    while(emu_cpu_parse(emu_cpu_get(e))) {
        v.push_back(&emu_cpu_get(e)->instr);
    }

    return v;
}

emulator.h (I changed the import paths)

#ifndef EMULATOR_H
#define EMULATOR_H 

#include <vector>

extern "C" {
#include "~/libemu/libemu/include/emu/emu.h"
#include "~/libemu/libemu/include/emu/emu_memory.h"
#include "~/libemu/libemu/include/emu/emu_cpu.h"
#include "~/libemu/libemu/include/emu/emu_log.h"
#include "~/libemu/libemu/include/emu/emu_instruction.h"
}

class Emulator {

public:
Emulator();
~Emulator();

void loadProgramInMemory(unsigned char instructionBytes[], int instructionBytesLen);
std::vector<struct emu_instruction*> getInstructionVector();
int runAndGetEFlags();
void printDebug();

private:
struct emu *e;
struct emu_memory *mem;
int static_offset;
};

#endif

I had to change the import paths in emu_instruction to make it compile.

The error I'm getting when trying to run this code is

emulator.cpp: In member function ‘std::vector<emu_instruction*> Emulator::getInstructionVector()’: emulator.cpp:29:29: error: invalid use of incomplete type ‘struct emu_cpu’ ~/libemu/libemu/include/emu/emu.h:45:8: error: forward declaration of ‘struct emu_cpu’

At this point I don't know what to do since I don't fully understand the error. Any help would be appreciated.

Adding the makefile.

Makefile:

CXX     = g++
CC      = g++

SRC = $(wildcard *.cpp)
OBJ = $(SRC:.cpp=.o)

# Executables 
PROGS   = program

all: $(PROGS)

program: program.o parser.o instruction.o emulator.o           /home/user/libemu/libemu/src/.libs/libemu.a
$(CXX) $(CXXFLAGS) program.o parser.o instruction.o emulator.o /home/user/libemu/libemu/src/.libs/libemu.a -ludis86 -o program.out

parser: parser.o instruction.o
$(CXX) $(CXXFLAGS) parser.o instruction.o -ludis86

clean:
rm -f *.o

cleaner: clean
rm -f $(PROGS) *.out

%.d: %.cpp
    @set -e; rm -f $@; \
    $(CXX) -MM $(CXXFLAGS) $< > $@.$$$$; \
    sed 's,\($*\)\.o[ :]*,\1.o $@ : ,g' < $@.$$$$ > $@; \
    rm -f $@.$$$$

Answer 1

It's really quite hard to guess what is 29th line of emulator.cpp, but I think your compilec can't locate the rest of libemu headers. Try to restore paths to emu_instruction to original and add into compiler line key like -I/home/user/libemu/libemu/include to point place with headers.

Answer 2

You must include emu_cpu_data.h that is where emu_cpu is actually defined.