TTF_OpenFont results in windows giving a heap corruption warning

Question

While trying to debug a program for heap corruption errors, I decided to use gflags in the Debugging Tools package for Windows as suggested in this stack overflow post. However, when I try to use this tool and enable full page heap checking by executing gflags -p /enable <program name> /full (with program name being my program's path), one of the libraries I use, SDL_ttf, throws an exception saying some variation of "Exception thrown at 0x6CD3D0FC (libfreetype-6.dll) in Jetfuel Graphical Example.exe: 0xC0000005: Access violation reading location 0x0A02A000" after the function TTF_OpenFont is used with valid arguments. Does this mean my version of SDL_TTF is causing my heap corruption errors, or does it mean my code is doing something wrong?

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Here is my code(When I was testing this, I had filename set correctly to "default.ttf", no face index, and font size set to 20):

#include "font.h"

namespace jetfuel {
    namespace draw {
        bool Font::m_ttfinit = false;

        Font::Font(const std::string filename) {
            m_filename = filename;

            m_isfontloaded = true;
        }

        Font::Font(const std::string filename, const long faceindex) {
            m_filename = filename;
            m_faceindex = faceindex;

            m_isfontloaded = true;
        }

        void Font::Load_font(const std::string filename){
            Set_file_name(filename);

            Set_is_font_loaded(true);
        }

        void Font::Load_font(const std::string filename, const long faceindex){
            Set_file_name(filename);
            Set_face_index(faceindex);

            Set_is_font_loaded(true);
        }

        void Font::Change_size(const unsigned int size){
            // Open Font with font index if index is set.

            if (!Get_ttf_init()) {
                if (TTF_Init() != 0) {
                    std::cerr << "SDL TTF ERROR:" << TTF_GetError() << "\n";
                    throw exceptions::SDL_ttf_exception();
                }

                Set_ttf_init(true);
            }

            if(Get_file_name()!=""){
                if (Get_ttf_font() != nullptr) {
                    TTF_CloseFont(Get_ttf_font());
                }

                std::string filename = Get_file_name();
                char *filenamecstring = new char[filename.length()+1];
                TTF_Font *ttffont;

                strcpy(filenamecstring, filename.c_str());

                SDL_ClearError();

                if(Get_face_index()!=-1){
                    ttffont = TTF_OpenFontIndex(filenamecstring, size,
                                                Get_face_index()); // And also can happen here!!
                }else{
                    ttffont = TTF_OpenFont(filenamecstring, size); // Error happens here!!
                }

                Set_ttf_font(ttffont);

                if(Get_ttf_font()==nullptr){
                    std::cerr << "SDL TTF ERROR:" << TTF_GetError() << "\n";
                    throw exceptions::SDL_ttf_exception();
                }
            }
        }
    } /* namespace draw */
} /* namespace jetfuel */

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And here are the versions of libraries and my OS:

• Windows 8.1 64-bit
• Visual Studio 2017 Community
• SDL 2.0.6
• SDL_ttf 2.0.14