If nothing else, argv[0] is useful for producing error messages that indicate the name of the executable that is outputting the message.
It's probably a good idea to not have it settable to other values by the invoking process, as is generally the case on Windows (ignoring its Posix subsystem here).
> It's probably a good idea to not have it settable to other values by the invoking process, as is generally the case on Windows (ignoring its Posix subsystem here).
Well there is an use case that I sometime use for setting argv[0]. Consider you want to run yourself as a subprocess. Why you want to do that? There are plenty of reasons, but in general the thing is that doing things after a fork() is not safe under some circumstances and thus sometimes you also want to exec yourself.
A technique is to then call yourself using another name in argv[0] for then in the main take a different flow from the normal command line parting, without adding an argument that the user can specify if it know that it exists.
Yes, I know that there are a ton of other methods to do the same thing (perhaps an environment variable, for example), but I find the method of argv[0] quite nice and simple to be fair.
You can set the full command line on windows independently from the program path using the standard Win32 CreateProcess(Ex) functions. This includes the part that ends up in argv[0] with your usual C runtime (Windows itself only provides a string and leaves it up to the program to split into arguments which may or may not use the standard CommandLineToArgv* functions - the standard C runtime doesn't and has slightly different escaping rules).
It's probably a good idea to not have it settable to other values by the invoking process, as is generally the case on Windows (ignoring its Posix subsystem here).