Eigen 示例代码无法通过 ARM 裸机编译

Question

I want to evaluate Eigen for a bare-metal ARM system. Here is what I'm trying to compile:

#include <Eigen/Dense>
using Eigen::MatrixXd;

void test()
{
  MatrixXd m(2,2);
  m(0,0) = 3;
  m(1,0) = 2.5;
  m(0,1) = -1;
  m(1,1) = m(1,0) + m(0,1);
}

Compilation gives me this:

phil@Mint-Virtual ~/Projects/Eigen $ /usr/bin/arm-none-eabi-g++ -I ./eigen-eigen-3.3.3 test.cpp -o test.o
In file included from ./eigen-eigen-3.3.3/Eigen/Dense:1:0,
                 from test.cpp:5:
./eigen-eigen-3.3.3/Eigen/Core:66:17: fatal error: new: No such file or directory
compilation terminated.

I am a C programmer, not C++, but I do understand that this is a library problem. I have looked at several references on using C++ on bare-metal systems, but frankly I'm still a bit puzzled about how to proceed. I would like to just stub out the missing stuff, which seems to be malloc(), free(), and etc., so that I can get a successful compile. I've tried using my own new.h with -nostdinc++ -include new.h on the compiler invocation, but that did not work.

Am I making a simple mistake, or is trying to use Eigen in this environment a fool's errand? Any guidance would be greatly appreciated.

Answer 1

The bare metal system does not have a memory allocator, so new and delete cannot be used. Code using fixed-size matrices should work:

#define EIGEN_NO_MALLOC
#include <Eigen/Dense>
using Eigen;

void test()
{
    Matrix2d m;
    m(0,0) = 3;
    m(1,0) = 2.5;
    m(0,1) = -1;
    m(1,1) = m(1,0) + m(0,1);
}

Answer 2

We make heavy use of Eigen C++ in our bare metal code for ARM systems. Your problem obviously is in general correlated to memory allocation not to Eigen itself. You can however implement this in a basic form to use most of fixed-size allocated C++ constructs with some simple mockup of new und delete . We used a construct like the following:

extern"C"
void *malloc(size_t){
    return (void*)(0);
}

extern"C"
void free(void*){};


// C++ mini-definition of new & delete and aeabi_atexit:
void* operator new(size_t size, const std::nothrow_t& nothrow_value)throw(){
    return malloc(size);
}

void* operator new(size_t size) {
    return malloc(size);
}

void operator delete(void* p) throw(){
    free(p);
}


extern"C"
int __aeabi_atexit(void*,void(*)(void*),void*){
    return 0;
}

Other resources You might consider:

• Practical guide to Bare Metal C++
• Effective C++ in an Embedded Environment

I would have posted more resources, but my account only allows two of them...