That is, the compiler uses the PCH file representing the most preprocessing directives from
the primary source file.
For example, a primary source file might begin with:
If there is one PCH file for xxx.h and a second for
xxx.h and yyy.h, the latter PCH file is
selected, assuming that both apply to the current compilation. Additionally, after the PCH
file for the first two headers is read in and the third is compiled, a new PCH file for all
three headers is created if the requirements for PCH file creation are met.