it's a little more general, I think, since one common use case for it is to use it on your own process in order to intercept calls to stdlib/OS code from libraries you don't control.
For example, in the bad old days I used detours to virtualize the windows registry so that I could do "fake installs" of COM components inside of a VB6 app, allowing it to run without an install and without administrator permissions. This worked by detouring all the Win32 registry APIs, which was sufficient to intercept registry accesses performed by the COM infrastructure.
For example, in the bad old days I used detours to virtualize the windows registry so that I could do "fake installs" of COM components inside of a VB6 app, allowing it to run without an install and without administrator permissions. This worked by detouring all the Win32 registry APIs, which was sufficient to intercept registry accesses performed by the COM infrastructure.