Re: svn commit: r16244 - in trunk: . subversion/clients/cmdline subversion/include subversion/libsvn_client subversion/libsvn_wc subversion/svnversion subversion/tests/clients/cmdline subversion/tests/clients/cmdline/svntest tools/examples

Branko Èibej <brane@xbc.nu> writes:

> O.K., see r16270. I'd appreciate it if someone could compile this with
> GCC again, just to make sure all warnings have gone away.

Switching on -O2 optimisation:

../svn/subversion/libsvn_wc/adm_files.c: In function 'svn_wc_is_adm_dir':
../svn/subversion/libsvn_wc/adm_files.c:72: warning: dereferencing type-punned pointer will break strict-aliasing rules
../svn/subversion/libsvn_wc/adm_files.c: In function 'svn_wc_set_adm_dir':
../svn/subversion/libsvn_wc/adm_files.c:101: warning: dereferencing type-punned pointer will break strict-aliasing rules
../svn/subversion/libsvn_wc/adm_files.c:102: warning: dereferencing type-punned pointer will break strict-aliasing rules
../svn/subversion/libsvn_wc/adm_files.c: In function 'v_extend_with_adm_name':
../svn/subversion/libsvn_wc/adm_files.c:141: warning: dereferencing type-punned pointer will break strict-aliasing rules

There's also a performance issue here. Any function that simply wants
to read the adm directory name now has to go through a CAS. The
default CAS implementation is the generic mutex based implementation
in apr_atomic.c, so that means that every time a file in the .svn
directory is accessed a mutex will need to locked and unlocked.
That's a *lot* of mutex operations, could this be a bottleneck? Linux
on x86 can use the asm versions, but that's not the default and
doesn't help other platforms.

-- 
Philip Martin
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