Disable Visual Studio exception modal window

Visual Studio executables built in Debug mode by default pop up modal debug windows if an unhandled exception occurs. This can be can be undesirable for reasons including:

• users having to close nuisance windows manually.
• CI runs hang if an exception occurs and the modal window appears.
• AI agents or automated tools may hang with unexpected modal windows.
• remotely operated systems: modal windows can be difficult to close if the modal window is accidentally off-screen.

Debug popups for exception handling can be disabled by C++ runtime library functions provided by Visual Studio described below. NOTE: missing DLL modal popups are fixed by the calling program such as CTest instead of this C++ method below.

Adding a few lines of code to the C++ program works around this issue by redirecting the error text to stderr console and not popping up the modal window.

• _CrtSetReportMode keeps the modal window from appearing.
• _CrtSetReportFile redirects the message text to stderr so that the message can be diagnosed.

This is also relevant to continuous integration systems such as GitHub Actions, which may hang with an unrealized modal dialog otherwise.

#ifdef _MSC_VER
#include <crtdbg.h>
#endif

int main(){
#ifdef _MSC_VER
    _CrtSetReportMode(_CRT_ASSERT, _CRTDBG_MODE_FILE);
    _CrtSetReportFile(_CRT_ASSERT, _CRTDBG_FILE_STDERR);
    _CrtSetReportMode(_CRT_WARN, _CRTDBG_MODE_FILE);
    _CrtSetReportFile(_CRT_WARN, _CRTDBG_FILE_STDERR);
    _CrtSetReportMode(_CRT_ERROR, _CRTDBG_MODE_FILE);
    _CrtSetReportFile(_CRT_ERROR, _CRTDBG_FILE_STDERR);
#endif

// rest of program
}