vcbuild.bat fails with "input line too long" #13765

• Version: master
• Platform: Windows x64 with Visual Studio 2015
• Subsystem: vcbuild

Running vcbuild.bat appends data to the PATH environment variable. After several runs, the value of the variable becomes so long that VC batch files crash with an error message saying "Input line is too long", which is not really surprising considering the relatively small limit of about 8k for command lines on Windows.

This line calls a number of batch scripts which configure the environment to use the VS2015 toolchain:

call "%VS140COMNTOOLS%\..\..\vc\vcvarsall.bat"

This answer might offer a solution to the problem:

if not defined DevEnvDir (
    call vcvarsall.bat
)

However, I am not too familiar with VC-internal batch files and have no idea about side-effects or alternatives, so any insights would be useful here.

@seishun was able to reproduce this on VS2015, but not on VS2017.