javascriptgoogle-chromev8emscriptenasm.js

emscripten: How to delete memory of std::vector allocated in C++ code


I want to know how to properly delete the memory of std::vector allocated in c++ code and passed to js as function return.

My c++ code is

#include <vector>
#include <emscripten/bind.h>

using namespace emscripten;

std::vector<int> intArrayToVector(uintptr_t input, int num){
std::vector<int> vec;
const int* ptr = reinterpret_cast<int*>(input);
for(int i=0; i<num; i++){
    int val = *(ptr+i);
    vec.push_back(val);
}
return vec;
}

EMSCRIPTEN_BINDINGS(test){
register_vector<int>("VectorInt");
function("intArrayToVector", &intArrayToVector, allow_raw_pointer<arg<0>>());  
}

My html code is

<html>
<body>
 <script src="test.js"></script>
 <script>
   var num = 6;
   var buf = Module._malloc(100);
   var arr = new Int8Array(num);
   for(var i=0; i<num; i++){
      arr[i] = i+2;
   }
Module.HEAP8.set(arr, buf);
var v = Module.intArrayToVector(buf, num);

for(var i=0; i<num; i++){
    console.log(v.get(i));
}
Module._free(buf);

v.resize(0, 0);
v.delete();  
v = {};
</script>
</body>
</html>

I tried the following code to delete the allocated memory but nothing is happening.

v.resize(0, 0);
v.delete();  
v = {};

Solution

  • I think v.delete() works.

    for (var j = 0;; j++) {
        var v = Module.intArrayToVector(buf, num);
    
        for(var i=0; i<num; i++){
            console.log(v.get(i));
        }
    }
    

    Above infinite loop aborts by Cannot enlarge memory arrays.

    But with v.delete() at end of loop, this program doesn't stop.