This is really weird. Here is what happened:
I have been using the X86 and X64 MSVC developer console )with Admin privilege) for a few months without any issue. I'm only using the cl.exe program to compile sample programs, such as:
cl 1_19_5_float.c /Fa1_19_5_float.asm /MD /Od /arch:IA32
15 minutes ago, I ran a few compiling and everything still worked fine. I left for 5 minutes, no one touched my computer and both consoles were kept open. Suddenly cl.exe failed to work. Every time I ran the command it kept telling me that "This app can't run on your PC", and showed "Access denied" in the console.
Is there any way to track the issue down? I absolutely have no idea what's going on. I checked the cl.exe under C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.29.30133\bin\Hostx86\x86 and C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.29.30133\bin\Hostx64\x64 and both are still there. TBH I only left for 5 minutes, what could go wrong? I even checked Event Viewer but nothing suspicious caught my eye. There was no Microsoft Update either.
OK I found what's wrong. There is an empty "cl.exe" and "cl" in the dev folder. I have absolutely how they got in in that 5 minutes. They might be malware more likely just glitches. Somehow, some commands created them.