rustc: Append platform exe suffix to output files

[alexcrichton]

Closes #15828

[lilyball]

How does this behave if the -o flag is provided? Also, is this the correct fix? It seems odd to me that you'd have to add logic like this to get filename printing to work, when it manages to generate the correct filename during compilation.

Looking at driver/mod.rs, it looks like printing the filename calls filename_for_input() with &t_outputs.with_extension("") as the output filename. Is the removal of the extension there not perhaps the real culprit?

[alexcrichton]

How does this behave if the -o flag is provided?

This method is not called if -o is provided

Also, is this the correct fix? It seems odd to me that you'd have to add logic like this to get filename printing to work, when it manages to generate the correct filename during compilation.

The windows linker we use translates -o foo to "oh, you mean -o foo.exe", which is why we produce .exe files. This is moving that logic into the compiler.

Is the removal of the extension there not perhaps the real culprit?

Nah that part is just chopping off the extension so the right one can be added later.

[liigo]

Q: How does this behave if the -o flag is provided?
A: This method is not called if -o is provided

This is not true. rustc -o hello2.xxx hello.rs will create file hello2.xxx,
but rustc -o hello2.xxx --print-file-name hello.rs prints hello2.exe.
@alexcrichton

[alexcrichton]

Could you open a bug on that? In general -o mixed with different names causes all sorts of weirdness.

[liigo]

#15935 if i didn't misunderstand.