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

On 2018-09-12 at 15:18, Erik Skultety wrote: >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. Okay. Then the syntax-check rule would be simpler. > >> >> 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 Okay. Just now, I find that we do not need to add a new rule. A minor change on sc_require_attribute_cleanup_initialization can work.