On Tue, 11 Apr 2017, Florian Weimer wrote: > On 04/06/2017 09:12 PM, Richard Biener wrote: > > > Right. The kernel also has many APIs which return multiple > > > variable-length data blocks, such as getdents64, and many more > > > interfaces in combination with read/recv system calls. Variable length > > > > > > means that you cannot declare the appropriate type after the first data > > > > > > item, so you technically have to use malloc. > > > > > > POSIX interfaces which exhibit a similar pattern are getpwnam_r and > > > friends, but for them, you can probably use malloc without ill effect > > > (although there are still performance concerns). > > > Can you give a concrete example which shows the issue and how > > typeless_storage helps? > > An example is in libffi/src/closures.c: > > char buf[MAXPATHLEN * 3]; > > if (getmntent_r (last_mntent, &mnt, buf, sizeof (buf)) == NULL) > return -1; > > The intent is that buf is untyped storage, from which the getmntent_r function > can allocate objects as needed (instead of using malloc). > > Based on your earlier comments, GCC already supports that without any further > source code annotations.
Yes. Richard.
