[CMake] Forcing C++: What Causes VC Warning D4025 : overriding /TP with /TC

[Steve Johns]

I'm building a project with an application directory and several library 
directories.

Code is a mix of .c and .cpp files.  Some of the directories contain only .c 
files.

I'm using VC 7.1.

I've used these lines in my CMakelists.txt files in order to force .c files 
to be compiled and linked as C++:

SET(CMAKE_C_COMPILER ${CMAKE_CXX_COMPILER})
SET_TARGET_PROPERITES( <tgt> PROPERTIES LINKER_LANGUAGE CXX)

yet, at build time, I get the error:

Warning D4025 : overriding /TP with /TC

and indeed, there is a /TC on the build command line after the /TP.

I don't want that /TC to be there, and I'd really love to know where it is 
coming from and how to avoid it.