Detected a memory leak.

[llcxiongmao]

Environment: Windows 10, 64bit, vs2022.

reproduce code:

#include <memory>

#include <Windows.h>
#include <crtdbg.h>

#include <FL/Fl.H>
#include <FL/Fl_Window.H>

int WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd) {
	// enable memory leak check.
	_CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);

	// _CrtSetBreakAlloc(162);

	std::unique_ptr<Fl_Window> win = std::make_unique<Fl_Window>(0, 0, 800, 600);
	win->show();

	Fl::run();

	win = nullptr;
	return 0;
}

leak position：src/Fl.cxx#1852, code:

void Fl::watch_widget_pointer(Fl_Widget *&w)
{
  Fl_Widget **wp = &w;
  int i;
  for (i=0; i<num_widget_watch; ++i) {
    if (widget_watch[i]==wp) return;
  }
  if (num_widget_watch==max_widget_watch) {
    max_widget_watch += 8;
    // widget_watch leaked.
    widget_watch = (Fl_Widget***)realloc(widget_watch, sizeof(Fl_Widget**)*max_widget_watch);
  }
  widget_watch[num_widget_watch++] = wp;
#ifdef DEBUG_WATCH
  printf ("\nwatch_widget_pointer:   (%d/%d) %8p => %8p\n",
    num_widget_watch,num_widget_watch,wp,*wp);
  fflush(stdout);
#endif // DEBUG_WATCH
}

i scan the entire project, find widget_watch never be freed.

[ManoloFLTK]

Thanks for reporting this finding.

That's how the FLTK library works. There are many places where FLTK allocates some memory, to hold a character string for example, and uses and re-uses that memory for the functioning of the library, and never releases it. That is to be considered part of the resources required by FLTK to access the OS and its displays. These are not memory leaks.