gcc precompiled headers weird behaviour with -c option

Question

Short story:

I can\'t make precompiled headers work properly with gcc -c option.

Long story:

Folks, I\'m using gcc-4.4.1 on Linux and before trying preco

Answer 1

Ok, I think I've found the solution: -fpch-preprocess should be used alongside with -c option. It works like a charm!

Here's the timings:

with pch

$ time g++ -I. -include pre.h -c foo.cpp -fpch-preprocess

real    0m0.028s
user    0m0.016s
sys 0m0.016s

without pch

$ time g++ -I. -c foo.cpp 

real    0m0.330s
user    0m0.292s
sys 0m0.044s

Update: I asked the same question on the gcc help mailing list and Ian Lance Taylor explained this strange behavior by my usage of distcc/ccache. These tools first preprocess the source that's why this options is required.