| Message ID | 20191229165108.2856915-1-samuel.thibault@ens-lyon.org |
|---|---|
| State | New |
| Headers | show |
| Series | [hurd,commited] hurd sendmsg: Fix warning on calling CMSG_*HDR | expand |
On Dez 29 2019, Samuel Thibault wrote: > diff --git a/sysdeps/mach/hurd/sendmsg.c b/sysdeps/mach/hurd/sendmsg.c > index 0c19b3223c..3d7317cec4 100644 > --- a/sysdeps/mach/hurd/sendmsg.c > +++ b/sysdeps/mach/hurd/sendmsg.c > @@ -108,7 +108,7 @@ __libc_sendmsg (int fd, const struct msghdr *message, int flags) > > /* Allocate enough room for ports. */ > cmsg = CMSG_FIRSTHDR (message); > - for (; cmsg; cmsg = CMSG_NXTHDR (message, cmsg)) > + for (; cmsg; cmsg = CMSG_NXTHDR ((struct msghdr *) message, cmsg)) Why is the first argument of __cmsg_nxthdr not const? Andreas.
Andreas Schwab, le dim. 29 déc. 2019 18:12:02 +0100, a ecrit: > > - for (; cmsg; cmsg = CMSG_NXTHDR (message, cmsg)) > > + for (; cmsg; cmsg = CMSG_NXTHDR ((struct msghdr *) message, cmsg)) > > Why is the first argument of __cmsg_nxthdr not const? I don't know, it is so on other systems as well. I guess an issue is that if it was const, CMSG_NXTHDR would only be allowed to return a const, and the caller might actually want a non-const (and it passed a non-const). So it'd be a choice between cast-parameter vs cast-returned-value. Samuel
On Dez 29 2019, Samuel Thibault wrote: > Andreas Schwab, le dim. 29 déc. 2019 18:12:02 +0100, a ecrit: >> > - for (; cmsg; cmsg = CMSG_NXTHDR (message, cmsg)) >> > + for (; cmsg; cmsg = CMSG_NXTHDR ((struct msghdr *) message, cmsg)) >> >> Why is the first argument of __cmsg_nxthdr not const? > > I don't know, it is so on other systems as well. > > I guess an issue is that if it was const, CMSG_NXTHDR would only > be allowed to return a const, The return value is not based on the first argument. Andreas.
Andreas Schwab, le dim. 29 déc. 2019 19:08:37 +0100, a ecrit: > On Dez 29 2019, Samuel Thibault wrote: > > > Andreas Schwab, le dim. 29 déc. 2019 18:12:02 +0100, a ecrit: > >> > - for (; cmsg; cmsg = CMSG_NXTHDR (message, cmsg)) > >> > + for (; cmsg; cmsg = CMSG_NXTHDR ((struct msghdr *) message, cmsg)) > >> > >> Why is the first argument of __cmsg_nxthdr not const? > > > > I don't know, it is so on other systems as well. > > > > I guess an issue is that if it was const, CMSG_NXTHDR would only > > be allowed to return a const, > > The return value is not based on the first argument. Oh, right. Then I don't know, I just see it so everywhere else. Samuel
* Andreas Schwab: > On Dez 29 2019, Samuel Thibault wrote: > >> diff --git a/sysdeps/mach/hurd/sendmsg.c b/sysdeps/mach/hurd/sendmsg.c >> index 0c19b3223c..3d7317cec4 100644 >> --- a/sysdeps/mach/hurd/sendmsg.c >> +++ b/sysdeps/mach/hurd/sendmsg.c >> @@ -108,7 +108,7 @@ __libc_sendmsg (int fd, const struct msghdr >> *message, int flags) >> >> /* Allocate enough room for ports. */ >> cmsg = CMSG_FIRSTHDR (message); >> - for (; cmsg; cmsg = CMSG_NXTHDR (message, cmsg)) >> + for (; cmsg; cmsg = CMSG_NXTHDR ((struct msghdr *) message, cmsg)) > > Why is the first argument of __cmsg_nxthdr not const? Some programmers expect that CMSG_NXTHDR can be used to construct ancillary data. See bug 13500.
On Dez 29 2019, Florian Weimer wrote: > * Andreas Schwab: > >> On Dez 29 2019, Samuel Thibault wrote: >> >>> diff --git a/sysdeps/mach/hurd/sendmsg.c b/sysdeps/mach/hurd/sendmsg.c >>> index 0c19b3223c..3d7317cec4 100644 >>> --- a/sysdeps/mach/hurd/sendmsg.c >>> +++ b/sysdeps/mach/hurd/sendmsg.c >>> @@ -108,7 +108,7 @@ __libc_sendmsg (int fd, const struct msghdr >>> *message, int flags) >>> >>> /* Allocate enough room for ports. */ >>> cmsg = CMSG_FIRSTHDR (message); >>> - for (; cmsg; cmsg = CMSG_NXTHDR (message, cmsg)) >>> + for (; cmsg; cmsg = CMSG_NXTHDR ((struct msghdr *) message, cmsg)) >> >> Why is the first argument of __cmsg_nxthdr not const? > > Some programmers expect that CMSG_NXTHDR can be used to construct > ancillary data. See bug 13500. How is that related to the first argument? Andreas.
diff --git a/sysdeps/mach/hurd/sendmsg.c b/sysdeps/mach/hurd/sendmsg.c index 0c19b3223c..3d7317cec4 100644 --- a/sysdeps/mach/hurd/sendmsg.c +++ b/sysdeps/mach/hurd/sendmsg.c @@ -108,7 +108,7 @@ __libc_sendmsg (int fd, const struct msghdr *message, int flags) /* Allocate enough room for ports. */ cmsg = CMSG_FIRSTHDR (message); - for (; cmsg; cmsg = CMSG_NXTHDR (message, cmsg)) + for (; cmsg; cmsg = CMSG_NXTHDR ((struct msghdr *) message, cmsg)) if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) nports += (cmsg->cmsg_len - CMSG_ALIGN (sizeof (struct cmsghdr))) / sizeof (int); @@ -119,7 +119,7 @@ __libc_sendmsg (int fd, const struct msghdr *message, int flags) nports = 0; for (cmsg = CMSG_FIRSTHDR (message); cmsg; - cmsg = CMSG_NXTHDR (message, cmsg)) + cmsg = CMSG_NXTHDR ((struct msghdr *) message, cmsg)) { if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS) {