Commenter S asks, "What happened to the return code from WinMain in a Windows 3.1 app?" After all, there was no
GetExitCodeProcess function in 16-bit Windows.
Basically, the exit code vanished into the ether.
Unless you captured it.
The Toolhelp library provided a low-level hook into various parts of the kernel, allowing you to monitor, among other things, the creation and destruction of tasks. That was how you captured the return code of a Windows program in 16-bit Windows.
But if you didn't catch it as it happened, it was gone forever, lost in the ether.