ccache - all files are "no input file"

Question

I'm using ccache version 3.7.4 compiled by me like this: ccache compiler [compiler options] but it doesn't seem to work

cache hit (direct)                     0
cache hit (preprocessed)               0
cache miss                             0
cache hit rate                      0.00 %
no input file                         20
cleanups performed                     0
files in cache                         0
cache size                           0.0 kB
max cache size                       5.0 GB

The only field increases is the "no input file" per each compiled file, from ccache help pages it means No input file was specified to the compiler which isn't clear to me.

ccache.conf looks like this:

max_size = 5G
cache_dir = /local/ccache
temporary_dir = /tmp/ccache
umask = 002
direct_mode = true

What am I missing ?

EDIT: found that I can see more debugs by setting CCACHE_LOGFILE. Now I see this debug line for each file:

File.cpp is not a regular file, not considering as input file
No input file found
Failed; falling back to running the real compiler

running: stat File.cpp File: `File.cpp' Size: 14924 Blocks: 32 IO Block: 1048576 regular file