Re: [libvirt] [PATCH 1/6] util: file: introduce VIR_AUTOCLOSE macro to close fd of the file automatically

On Tue, Sep 11, 2018 at 10:31:18PM +0800, Shi Lei wrote: > On 2018-09-11 at 20:22, Michal Privoznik wrote: >> On 09/10/2018 05:47 AM, Shi Lei wrote: >>> By making use of GNU C's cleanup attribute handled by the VIR_AUTOCLOSE macro, >>> many of the VIR_FORCE_CLOSE calls can be dropped, which in turn leads to >>> getting rid of many of our cleanup sections. >>> >>> Signed-off-by: Shi Lei <shi_lei(a)massclouds.com&gt; >>> --- >>>   src/util/virfile.h | 20 ++++++++++++++++++-- >>>   1 file changed, 18 insertions(+), 2 deletions(-) >>> >>> diff --git a/src/util/virfile.h b/src/util/virfile.h >>> index b30a1d3..70e7203 100644 >>> --- a/src/util/virfile.h >>> +++ b/src/util/virfile.h >>> @@ -54,6 +54,11 @@ int virFileClose(int *fdptr, virFileCloseFlags flags) >>>   int virFileFclose(FILE **file, bool preserve_errno) ATTRIBUTE_RETURN_CHECK; >>>   FILE *virFileFdopen(int *fdptr, const char *mode) ATTRIBUTE_RETURN_CHECK; >>> >>> +static inline void virForceCloseHelper(int *_fd) >> >> No need for this argument to have underscore in its name. > > Okay. > >> >>> +{ >>> +    ignore_value(virFileClose(_fd, VIR_FILE_CLOSE_PRESERVE_ERRNO)); >>> +} >>> + >>>   /* For use on normal paths; caller must check return value, >>>      and failure sets errno per close. */ >>>   # define VIR_CLOSE(FD) virFileClose(&(FD), 0) >>> @@ -64,8 +69,7 @@ FILE *virFileFdopen(int *fdptr, const char *mode) ATTRIBUTE_RETURN_CHECK; >>> >>>   /* For use on cleanup paths; errno is unaffected by close, >>>      and no return value to worry about. */ >>> -# define VIR_FORCE_CLOSE(FD) \ >>> -    ignore_value(virFileClose(&(FD), VIR_FILE_CLOSE_PRESERVE_ERRNO)) >>> +# define VIR_FORCE_CLOSE(FD) virForceCloseHelper(&(FD)) >>>   # define VIR_FORCE_FCLOSE(FILE) ignore_value(virFileFclose(&(FILE), true)) >>> >>>   /* Similar VIR_FORCE_CLOSE() but ignores EBADF errors since they are expected >>> @@ -80,6 +84,18 @@ FILE *virFileFdopen(int *fdptr, const char *mode) ATTRIBUTE_RETURN_CHECK; >>>                    VIR_FILE_CLOSE_PRESERVE_ERRNO | \ >>>                    VIR_FILE_CLOSE_DONT_LOG)) >>> >>> +/** >>> + * VIR_AUTOCLOSE: >>> + * @fd: fd of the file to be closed automatically >>> + * >>> + * Macro to automatically force close the fd by calling virForceCloseHelper >>> + * when the fd goes out of scope. It's used to eliminate VIR_FORCE_CLOSE >>> + * in cleanup sections. >>> + */ >>> +# define VIR_AUTOCLOSE(fd) \ >>> +    __attribute__((cleanup(virForceCloseHelper))) int fd = -1 >> >> While this may helps us to initialize variables correctly, I think we >> should do that explicitly. Not only it follows what VIR_AUTOFREE is >> doing, it also is more visible when used. For instance, in 2/6 when the >> macro is used for the first time, it's not visible what is @fd >> initialized to. > > Okay. So I think the macro could be like: > > # define VIR_AUTOCLOSE \ >    __attribute__((cleanup(virForceCloseHelper))) int Actually, I'd prefer if we stayed consistent with the existing AUTO_ macros, IOW, the form of VIR_AUTOCLOSE(fd) = <rvalue> is IMHO desired.