Date: Thu, 28 Jun 2018 13:45:24 -0500 From: Justin Hibbits <jrh29@alumni.cwru.edu> To: dab@freebsd.org Cc: src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r335765 - head/sys/sys Message-ID: <CAHSQbTD5BtcvcMeA%2BZeAUfkdsB6F%2BY9G182rnOHwb-E%2ByGxCUw@mail.gmail.com> In-Reply-To: <201806281701.w5SH15eP011261@repo.freebsd.org> References: <201806281701.w5SH15eP011261@repo.freebsd.org>
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Hi David, On Thu, Jun 28, 2018 at 12:01 PM David Bright <dab@freebsd.org> wrote: > > Author: dab > Date: Thu Jun 28 17:01:04 2018 > New Revision: 335765 > URL: https://svnweb.freebsd.org/changeset/base/335765 > > Log: > Remove potential identifier conflict in the EV_SET macro. > > PR43905 pointed out a problem with the EV_SET macro if the passed > struct kevent pointer were specified with an expression with side > effects (e.g., "kevp++"). This was fixed in rS110241, but by using a > local block that defined an internal variable (named "kevp") to get > the pointer value once. This worked, but could cause issues if an > existing variable named "kevp" is in scope. To avoid that issue, > jilles@ pointed out that "C99 compound literals and designated > initializers allow doing this cleanly using a macro". This change > incorporates that suggestion, essentially verbatim from jilles@ > comment on PR43905, except retaining the old definition for pre-C99 or > non-STDC (e.g., C++) compilers. > > PR: 43905 > Submitted by: Jilles Tjoelker (jilles@) > Reported by: Lamont Granquist <lamont@scriptkiddie.org> > Reviewed by: jmg (no comments), jilles > MFC after: 1 week > Sponsored by: Dell EMC > Differential Revision: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=43905 > > Modified: > head/sys/sys/event.h > > Modified: head/sys/sys/event.h > ============================================================================== > --- head/sys/sys/event.h Thu Jun 28 15:30:51 2018 (r335764) > +++ head/sys/sys/event.h Thu Jun 28 17:01:04 2018 (r335765) > @@ -49,7 +49,26 @@ > #define EVFILT_EMPTY (-13) /* empty send socket buf */ > #define EVFILT_SYSCOUNT 13 > > +#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L > #define EV_SET(kevp_, a, b, c, d, e, f) do { \ > + *(kevp_) = (struct kevent){ \ > + .ident = (a), \ > + .filter = (b), \ > + .flags = (c), \ > + .fflags = (d), \ > + .data = (e), \ > + .udata = (f), \ > + .ext[0] = 0, \ > + .ext[1] = 0, \ > + .ext[2] = 0, \ > + .ext[3] = 0, \ > + }; \ > +} while(0) > +#else /* Pre-C99 or not STDC (e.g., C++) */ > +/* The definition of the local variable kevp could possibly conflict > + * with a user-defined value passed in parameters a-f. > + */ > +#define EV_SET(kevp_, a, b, c, d, e, f) do { \ > struct kevent *kevp = (kevp_); \ > (kevp)->ident = (a); \ > (kevp)->filter = (b); \ > @@ -62,6 +81,7 @@ > (kevp)->ext[2] = 0; \ > (kevp)->ext[3] = 0; \ > } while(0) > +#endif > > struct kevent { > __uintptr_t ident; /* identifier for this event */ > This breaks gcc builds, with the following errors: 18:02:13 /usr/src/bin/pwait/pwait.c: In function 'main': 18:02:13 /usr/src/bin/pwait/pwait.c:144: warning: initialized field overwritten 18:02:13 /usr/src/bin/pwait/pwait.c:144: warning: (near initialization for '(anonymous).ext') 18:02:13 /usr/src/bin/pwait/pwait.c:144: warning: initialized field overwritten 18:02:13 /usr/src/bin/pwait/pwait.c:144: warning: (near initialization for '(anonymous).ext') 18:02:13 /usr/src/bin/pwait/pwait.c:144: warning: initialized field overwritten 18:02:13 /usr/src/bin/pwait/pwait.c:144: warning: (near initialization for '(anonymous).ext') 18:02:13 /usr/src/bin/pwait/pwait.c:158: warning: initialized field overwritten 18:02:13 /usr/src/bin/pwait/pwait.c:158: warning: (near initialization for '(anonymous).ext') 18:02:13 /usr/src/bin/pwait/pwait.c:158: warning: initialized field overwritten 18:02:13 /usr/src/bin/pwait/pwait.c:158: warning: (near initialization for '(anonymous).ext') 18:02:13 /usr/src/bin/pwait/pwait.c:158: warning: initialized field overwritten 18:02:13 /usr/src/bin/pwait/pwait.c:158: warning: (near initialization for '(anonymous).ext') This can be seen in the tinderbox (https://ci.freebsd.org/tinderbox) I encountered this as a failure in building usr.sbin/camdd, which shows the same type of error. - Justin
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