What is the difference between the LIB and LIBPATH environment variables for MS Visual C/C++?

Question

I've been working on some build scripts, and this is bugging me. I want to be sure that we're independent of environment settings, but in order to be sure of that I feel a need to understand how/where the settings are used by the tools.

The Visual Studio command prompt and/or vcvarsall.bat file set up two distinct environment variables: LIB and LIBPATH. The values are different, but partially overlapping. Here are the values from my system:

LIB=C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\LIB;C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\ATLMFC\LIB;C:\Program Files (x86)\Windows Kits\8.0\lib\win8\um\x86;  LIBPATH=C:\Windows\Microsoft.NET\Framework\v4.0.30319;C:\Windows\Microsoft.NET\Framework\v3.5;C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\LIB;C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\ATLMFC\LIB;C:\Program Files (x86)\Windows Kits\8.0\References\CommonConfiguration\Neutral;\Microsoft.VCLibs\11.0\References\CommonConfiguration\neutral; 

I'd just like to understand the rationale for having two different variables -- a little more than the obvious fact that LIBPATH brings in more libs. I've tried looking it up, but I haven't found a clear definition of when each is used by the linker and/or the dev environment.

Answer 1

LIB is for the linker, helps it find import and static libraries.

LIBPATH is for the compiler, helps it find metadata files. Like type libraries, .NET assemblies, WinRT .winmd files.