Android JNI print int64_t to file

Question

I am trying to use JNI code to print Android sensor timestamps to a file.

The timestamps are defined as int64_t.

The line to print the timestamp is:

fout<<timestamp<<std::endl;

Where fout is an open file stream in output mode.

When I try to compile, the following error results:

ambiguous overload for 'operator<<' (operand types are 'std::ofstream {aka std::basic_ofstream >}' and 'int64_t {aka long long int}') XXX.cpp /YYY/jni line ZZZ C/C++ Problem

I thought I would make an MWE for this using standard C++:

#include <iostream>
#include <cstdint>

int main(){
  int64_t a;
  std::cin>>a;
  std::cout<<a<<std::endl;
}

But this compiles without an issue, which makes me think the problem is somehow in the way Eclipse compiles the code.

I am inside Eclipse 3.8.1. My default compiler is GCC 4.9.2.

The compiler knows that a=42. Try to store a timestamp there. — 18446744073709551615, Oct 13 '15 at 07:00
@18446744073709551615: I've modified the code so that it takes a user input, preventing the compiler from optimizing on the constant. — Richard, Nov 25 '15 at 01:44

score 0 · Answer 1 · answered Nov 25 '15 at 02:22

I solved this problem by going into jni/Application.mk and using this line:

LOCAL_CPPFLAGS += -std=gnu++11

instead of this line:

LOCAL_CPPFLAGS+=-std=c++11.

Some have conjectured that the problem is due to different mappings of long long int in stlport.

Android JNI print int64_t to file

1 Answers1