Turns out I _really_ underestimated the impact of
--include-headers-for-types, as it significantly reduces both runtime
and storage penalties. For example, on my machine the runtime of
uncached run goes down from ~15 minutes to ~2 minutes, and similarly the
total storage needed by the cache goes from ~15 GiB down to ~3 GiB.
Drop the original macro file, since it's not needed anymore thanks to
resolving includes properly, but introduce a similar file -
parsing_hacks.h - that helps Coccinelle in some specific corner cases.
This eliminates most of the outstanding parsing errors in source files.
The remaining ones are limitations of the parsing engine (see the FIXMEs
in pasing_hacks.h) and need further investigation.
Since Coccinelle is originally a kernel tool, it doesn't search the
system include path by default for header files. Without this we're
missing a lot of types provides by stdlib (and other libraries we make
use of).
Turns out that the original way we did things was quite broken, as it
skipped a _lot_ of code. This was because we just threw everything into
one pile and tried to spatch it, but this made Coccinelle sad, like when
man page examples redefined some of our macros, causing typedef
conflicts.
For example, with a minimal reproducer that defines a cleanup macro in
two source files, Coccinelle has no issues when spatch-ing each one
separately:
$ spatch --verbose-parsing --sp-file zz-drop-braces.cocci main.c
init_defs_builtins: /usr/lib64/coccinelle/standard.h
HANDLING: main.c
SPECIAL NAMES: adding _cleanup_ as a attribute with arguments
SPECIAL NAMES: adding _cleanup_free_ as a attribute
$ spatch --verbose-parsing --sp-file zz-drop-braces.cocci
logcontrol-example.c
init_defs_builtins: /usr/lib64/coccinelle/standard.h
HANDLING: logcontrol-example.c
SPECIAL NAMES: adding _cleanup_ as a attribute with arguments
But when you try to spatch both of them at once, Coccinelle starts
complaining and skipping the "bad" code:
$ spatch --verbose-parsing --sp-file zz-drop-braces.cocci main.c logcontrol-example.c
init_defs_builtins: /usr/lib64/coccinelle/standard.h
HANDLING: main.c logcontrol-example.c
SPECIAL NAMES: adding _cleanup_ as a attribute with arguments
SPECIAL NAMES: adding _cleanup_free_ as a attribute
remapping: _cleanup_ to an ident in macro name
ERROR-RECOV: found sync end of #define, line 44
parsing pass2: try again
ERROR-RECOV: found sync end of #define, line 44
parse error
= File "logcontrol-example.c", line 44, column 21, charpos = 1719
around = '__attribute__',
whole content = #define _cleanup_(f) __attribute__((cleanup(f)))
badcount: 2
bad: #include <systemd/sd-journal.h>
bad:
BAD:!!!!! #define _cleanup_(f) __attribute__((cleanup(f)))
This was, unfortunately, hidden as it is visible only with
--verbose-parsing (or --parse-error-msg).
Another issue was how we handled includes. The original way of throwing
them into the pile of source files doesn't really work, leading up to
similar issues as above. The better way is to let Coccinelle properly
resolve all includes by telling it where to find our own include files
(basically the same thing we already do during compilation).
After fixing all this, Coccinelle now has a chance to process much more
of our code (there are still some issues in more complex macros, but
that requires further investigation). However, there's a huge downside
from all of this - doing a _proper_ code analysis is surprisingly time
and resource heavy; meaning that processing just one Coccinelle rule now
takes 15 - 30 minutes.
To make this slightly less painful, Coccinelle supports caching the
generated ASTs, which actually helps a lot - it gets the runtime of one
rule from 15 - 30 minutes down to ~1 minute. It, of course, has its own
downside - the cache is _really_ big (ATTOW the cache takes ~15 GiB).
However, even with the aggressive AST caching you're still looking at
~1 hour for one full Coccinelle run, which is a bit annoying, but I
guess that's the price of doing things _properly_ (but I'll definitely
look into ways of further optimizing this).
Yu Watanabe
Frantisek Sumsal
Luca Boccassi
Mike Yuan
David Tardon
Stuart Hayhurst