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.

> > And the statement is like: > > VIR_AUTOCLOSE fd = -1; > VIR_AUTOCLOSE sock_fd = socket(VIR_NETDEV_FAMILY, SOCK_DGRAM, 0); > > Also, I think I should add a new syntax-check rule to ensure the initialization > of the variable. Just like sc_require_attribute_cleanup_initialization > for VIR_AUTO(FREE|PTR). Yep, I agree with adding a similar syntax-check rule. Erik