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Quick update - looks like it's not the hardware API at all, and I
guess not erlang either, but Objective-C/Foundation stuff related to
how I was initialising CFStringRef values whose addresses I passed
to the API call. I was using a CFSTR macro that I took from an Apple
code sample; now I'm using a CFString function to do it and it's
working fine across the erlang & OS versions.<br>
<br>
I'm a bit baffled as to why the macro was working at all on R18, and
why it still works in the minimal C program version, as it looks to
me like it returns an immutable string ref; maybe it shouldn't work,
but like I say, I took it from an Apple sample. I plan to look into
that a bit more deeply.<br>
<br>
I'm also pretty baffled as to why the different erlang &
OS/compiler versions made this manifest, when it wasn't previously -
but regardless, taking it out seems to have side-stepped the
problem.<br>
<br>
Thanks everyone,<br>
<br>
best,<br>
Igor<br>
<br>
<div class="moz-cite-prefix">On 19/04/2017 13:33, Igor Clark wrote:<br>
</div>
<blockquote
cite="mid:ea67b83d-11e5-f19e-87e9-b8b92e937b41@gmail.com"
type="cite">
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
Hi folks, just checking in, I wonder if anyone has any further
thoughts about this?<br>
<br>
To re-state: the identical Mac OS C API call inside a NIF succeeds
(returns a valid string property) on R18/El Capitan, fails
(returns null) inside the same NIF on R19/El Capitan &
R18/R19/Sierra, yet succeeds in a minimal C program on both El
Capitan (clang/LLVM 8.0.0) and Sierra (clang/LLVM 8.1.0). In all
cases this happens regardless of whether the C API call is made
inside the main thread or a separate thread.<br>
<br>
Would be really grateful for any suggestions, as this is way
lower-level than I'm familiar with - happy to dig around further,
but a bit lost where to look next.<br>
<br>
Thanks!<br>
Igor<br>
<br>
<div class="moz-cite-prefix">On 18/04/2017 07:54, Igor Clark
wrote:<br>
</div>
<blockquote
cite="mid:CADskkxw4EGOARo99qrirh+NHkH-3-BT5A_mfK6nW3NA-NVcUFA@mail.gmail.com"
type="cite">
<div dir="ltr">Sorry, to be clearer, that should have read "<span
style="font-size:12.800000190734863px">when run in a
separate thread in the NIF using enif_thread_create(), the
API call succeeds under R18 on El Capitan, fails under R19
on El Capitan, and fails under R18 and R19 on Sierra".</span></div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Tue, Apr 18, 2017 at 7:52 AM, Igor
Clark <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:igor.clark@gmail.com" target="_blank">igor.clark@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000"> Thanks Paul and
Daniel,<br>
<br>
Just tested this: the exact same thing happens with
threads as without. The API call succeeds when run in a
separate thread in the minimal C program using
pthread_create(), on both El Capitan and Sierra; when
run in a separate thread in the NIF using
enif_thread_create(), the API call succeeds under R18 on
El Capitan and fails under R19.<br>
<br>
(My NIF code hasn't been explicitly creating or using
any threads at all until now, if that makes any
difference.)<br>
<br>
Does that give any further clues?<br>
<br>
Cheers,<br>
Igor
<div>
<div class="h5"><br>
<br>
<div class="m_2753930781096260743moz-cite-prefix">On
18/04/2017 03:47, Daniel Goertzen wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Following Paul's idea, what happens
in both the NIF and your minimal C program if
you first launch a new thread and call the API
from there?</div>
<br>
<div class="gmail_quote">
<div dir="ltr">On Mon, Apr 17, 2017 at 5:52 PM
Fisher, Paul <<a moz-do-not-send="true"
href="mailto:pfisher@alertlogic.com"
target="_blank">pfisher@alertlogic.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0
0 0 .8ex;border-left:1px #ccc
solid;padding-left:1ex">
<div>
<div>
<div
id="m_2753930781096260743m_-2395972316349742208x_compose-container"
style="direction:ltr"> <span><span></span></span>
<div>
<div style="direction:ltr">Complete
wild guess, but is there a
difference in nif initialization
running off the main thread in
non-working version? This would be a
problem for some low-level Mach
related things. Not near laptop to
look through the code to see if that
changed.</div>
<div><br>
</div>
<div><br>
</div>
<div
class="m_2753930781096260743m_-2395972316349742208x_acompli_signature">Get
<a moz-do-not-send="true"
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face="Calibri, sans-serif"
color="#000000"><b>From:</b> <a
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target="_blank">erlang-questions-bounces@<wbr>erlang.org</a>
<<a moz-do-not-send="true"
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on behalf of Igor Clark <<a
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target="_blank">igor.clark@gmail.com</a>><br>
<b>Sent:</b> Monday, April 17, 2017
4:38:11 PM<br>
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<b>Subject:</b> [erlang-questions]
NIF+device problem moving R18->R19
/ Mac 10.11->10.12</font>
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style="font-size:10pt">
<div
class="m_2753930781096260743m_-2395972316349742208PlainText">Hi
all,<br>
<br>
I'm having problems updating a NIF to
work correctly with R19 and/or <br>
MacOS Sierra (10.12). The NIF uses Mac
OS C API calls to talk to some <br>
hardware. It's been working just fine
with R18 on El Capitan, but it <br>
fails in a manner I don't understand
when I trying to run it on R19 or <br>
Sierra. I'm pretty baffled as to
what's going on, and wonder if any of
<br>
the following might ring bells or set
off a spider-sense for anyone here?<br>
<br>
- The code continues to work 100% as
expected on R18 / Mac OS El Capitan <br>
(10.11), as it has for the last year
or so.<br>
<br>
- On R19 on El Capitan, 99% of the C
code works as before, but one <br>
particular MacOS C API call fails
unexpectedly. It doesn't crash or <br>
cause errors directly, but it returns
null instead of a valid value as <br>
before. There are no build errors or
warnings. (I'm using 'pc' plugin <br>
version 1.5.0 with rebar3). Other
MacOS API calls talking to the same <br>
hardware work as expected, sending
correct commands, getting the <br>
hardware to carry out operations as
expected and returning expected <br>
values, without any problems.<br>
<br>
- On both R18 & R19 on Sierra,
exactly the same problem occurs as
above <br>
in R19 on El Capitan.<br>
<br>
- If I make the failing/null-returning
OS API call in a plain, <br>
simple-as-possible C file compiled
with gcc (Apple LLVM/clang), it works
<br>
as expected, *on both OS versions*.<br>
<br>
- If I paste that same
simple-as-possible C code verbatim
into the NIF, <br>
as the first line in the load()
function, and run it on R18/El
Capitan, <br>
it continues to work as expected.<br>
<br>
- If I then try to run that identical
pasted-verbatim NIF code with no <br>
changes on R18/Sierra or on R19 &
either OS version, this one particular
<br>
function call fails, as above.<br>
<br>
I realise it could be many things, and
my initial thought was that it <br>
must be the OS change or even the
hardware failing - but the hardware <br>
and C API call continue to work just
fine on both OS versions when the <br>
NIF stuff is taken out of the picture,
and on El Capitan, the <br>
previously-not-happening problem
reliably (and only) starts happening <br>
when I switch from R18 to R19.<br>
<br>
Did anything change between R18 and
R19 that might somehow make some, <br>
but not all, external C function calls
fail on El Capitan/clang 8.0.0? <br>
And could that be something that also
makes the same thing happen on <br>
both R18 and R19 under Sierra/clang
8.1.0? Could it perhaps be something <br>
do with the port compiler & LD/CXX
flags?<br>
<br>
Any ideas as to where else I could
look to try to track this down, or <br>
what might be causing this?<br>
<br>
(BTW, I'm using homebrew erlang, and
I've tried all the above with <br>
versions 18.1, 18.3, 19.0.2 and 19.3
on both OS versions. The gcc/clang <br>
version on El Capitan is from Xcode
8.1, "Apple LLVM version 8.0.0 <br>
(clang-800.0.42.1)". On Sierra it's
from Xcode 8.3.1, "Apple LLVM <br>
version 8.1.0 (clang-802.0.41)" - but
as above, the plain/non-NIF C code <br>
works perfectly and identically on
both versions.)<br>
<br>
Thanks very much,<br>
Igor<br>
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