On Wed, 11 Feb 2026 20:22:03 -0500 Dan Cross <[email protected]> wrote:
> On Wed, Feb 11, 2026 at 1:44 PM Ori Bernstein <[email protected]> wrote: > > On Wed, 11 Feb 2026 09:22:06 -0500 Dan Cross <[email protected]> wrote: > > > On Tue, Feb 10, 2026 at 10:34 PM Ori Bernstein <[email protected]> > > > wrote: > > > > On Tue, 10 Feb 2026 05:13:47 -0500 > > > > "Alyssa M via 9fans" <[email protected]> wrote: > > > > > > > > > On Monday, February 09, 2026, at 3:24 PM, ron minnich wrote: > > > > > > as for mmap, there's already a defacto mmap happening for > > > > > > executables. They are not read into memory. In fact, the first > > > > > > instruction you run in a binary results in a page fault. > > > > > I thinking one could bring the same transparent/defacto memory > > > > > mapping to read(2) and write(2), so the API need not change at all. > > > > > > > > That gets... interesting, from an FS semantics point of view. > > > > What does this code print? Does it change with buffer sizes? > > > > > > > > fd = open("x", ORDWR); > > > > pwrite(fd, "foo", 4, 0); > > > > read(fd, buf, 4); > > > > pwrite(fd, "bar", 4, 0); > > > > print("%s\n", buf); > > > > > > It depends. Is `buf` some buffer on your stack or something similar > > > (a global, static buffer, or heap-malloc'ed perhaps)? If so, > > > presumably it still prints "foo", since the `read` would have copied > > > the data out of any shared region and into process-private memory. Or, > > > is it a pointer to the start of some region that you mapped to "x"? > > > In that case, the whole program is suspect as it seems to operate well > > > outside of the assumptions of C, but on Plan 9, I'd kind of expect it > > > to print "bar". > > > > In this example, no trickery; single threaded code, nothing fancy. > > Ok. Perhaps implicitly you also mean that there's no `mmap` involved? The message I was responding to said: "I thinking one could bring the same transparent/defacto memory mapping to read(2) and write(2), so the API need not change at all." So, yes, I was talking about a hypothetical modification to read/write. -- Ori Bernstein <[email protected]> ------------------------------------------ 9fans: 9fans Permalink: https://9fans.topicbox.com/groups/9fans/Te8d7c6e48b5c075b-Mc7cc7ad5c35d413ea7182980 Delivery options: https://9fans.topicbox.com/groups/9fans/subscription
