Re-opening bug.

scanf has proven to be really difficult to modify.  I will try to take a look at this on the weekend.

Thanks for reporting this warning.  It is, in this case, an actual fault in the logic.  There are still two other scanf bugs outstanding and the resolution of those will require fixing this as well.

Thanks, the NA is now correct, but now bug #63467 is causing a duplicate at the end.  Unfortunately, correcting the duplicate is going to be harder and I'm going to have to change function signatures.

OK, on Fedora 37/aarch64:

octave:1> version -hgid
ans = deb553ac2c54
octave:2> [val, count, msg, pos] = sscanf ('2 na 3', '%f');
 assert (val, [2; NA; 3]);

 # This time NA at end
 [val, count, msg, pos] = sscanf ('2 3 na', '%f');
 assert (val, [2; 3; NA]);
error: ASSERT errors for:  assert (val,[2; 3; NA])

  Location  |  Observed  |  Expected  |  Reason
     .          O(2x1)       E(3x1)      Dimensions don't match
octave:6> sscanf ('2 3 na', '%f')
ans =

   2
   3

octave:7>

With the patch

octave:1> version -hgid
ans = deb553ac2c54+
octave:2> [val, count, msg, pos] = sscanf ('2 na 3', '%f');
 assert (val, [2; NA; 3]);

 # This time NA at end
 [val, count, msg, pos] = sscanf ('2 3 na', '%f');
 assert (val, [2; 3; NA]);
error: ASSERT errors for:  assert (val,[2; 3; NA])

  Location  |  Observed  |  Expected  |  Reason
     .          O(4x1)       E(3x1)      Dimensions don't match
octave:6> sscanf ('2 3 na', '%f')
ans =

     2
     3
    NA
    NA

Dmitri.
--

Can you try the attached patch: 63383.diff?

(file #54066)

Can you run just

sscanf ('2 3 na', '%f')

so I can see the output.  I expect it is only picking up the "2 3" and ignoring the "na", but always good to confirm.

It generally handles NAs fine except some weird cases like this one and https://savannah.gnu.org/bugs/?61358

I am rebooting it to Fedora, see if it is is there as well.

Dmitri.
--

I have a couple regressions on aarch64 (Ubuntu 22.10) hgid ab33554f97d2

octave:1> test ../test/io.tst
***** test <*63383>
 [val, count, msg, pos] = sscanf ('2 3 n', '%f');
 assert (val, [2; 3]);
 assert (count, 2);
 assert (msg, 'sscanf: format failed to match');
 assert (pos, 5);
 [val, count, msg, pos] = sscanf ('2 3 na', '%f');
 assert (val, [2; 3; NA]);
 assert (count, 3);
 assert (msg, '');
 assert (pos, 7);
 [val, count, msg, pos] = sscanf ('2 3 nan', '%f');
 assert (val, [2; 3; NaN]);
 assert (count, 3);
 assert (msg, '');
 assert (pos, 8);
!!!!! regression: https://octave.org/testfailure/?63383
ASSERT errors for:  assert (val,[2; 3; NA])

  Location  |  Observed  |  Expected  |  Reason
     .          O(2x1)       E(3x1)      Dimensions don't match
***** test <*63383>
 [val, count, msg, pos] = sscanf ('+NA -NA 1 +NAN -NAN', '%f');
 assert (val, [NA; NA; 1; NaN; NaN]);
 assert (count, 5);
 assert (msg, '');
 assert (pos, 20);
 [val, count, msg, pos] = sscanf ('-NA', '%f');
 assert (val, NA);
 assert (count, 1);
 assert (msg, '');
 assert (pos, 4);
 [val, count, msg, pos] = sscanf ('+NA', '%f');
 assert (val, NA);
 assert (count, 1);
 assert (msg, '');
 assert (pos, 4);
 [val, count, msg, pos] = sscanf ('-NaN', '%f');
 assert (val, NaN);
 assert (count, 1);
 assert (msg, '');
 assert (pos, 5);
 [val, count, msg, pos] = sscanf ('+NaN', '%f');
 assert (val, NaN);
 assert (count, 1);
 assert (msg, '');
 assert (pos, 5);
!!!!! regression: https://octave.org/testfailure/?63383
ASSERT errors for:  assert (val,NA)

  Location  |  Observed  |  Expected  |  Reason
     .          O(0x1)       E(1x1)      Dimensions don't match
warning: test: file /home/uu1/src/octave/test/io.tst leaked global variables: __assert_printf__
PASSES 173 out of 175 tests
octave:2> version -hgid
ans = ab33554f97d2

Dmitri.
--

I finally finished work on the scanf set of function (last changeset: http://hg.savannah.gnu.org/hgweb/octave/rev/2f08a53e0a23).  Everything should be working on the development branch now (Octave 9).  The changes were deemed too uncertain to be placed on the stable branch (Octave 8.1) a mere month ahead of an expected release.  However, with more testing they should be able to be a part of the 8.2 bug fix release.

Marking bug as Fixed and closing report.

the scanf parsing is complex and distributed across functions in libinterp and in liboctave.  Using the debugger, it appears that reading a double in liboctave is correctly setting the fail bit on the input stream.  However, back in libinterp the test for the fail condition is specifically disabled if the failure occurs at the EOF.

if (! is.eof () && is.rdstate () & std::ios::failbit)

Removing the eof() test with this patch makes things work for this bug report.

diff --git a/libinterp/corefcn/oct-stream.cc b/libinterp/corefcn/oct-stream.cc
--- a/libinterp/corefcn/oct-stream.cc
+++ b/libinterp/corefcn/oct-stream.cc
@@ -5042,7 +5042,8 @@ namespace octave

                     // If it looks like we have a matching failure, then
                     // reset the failbit in the stream state.
-                    if (! is.eof () && is.rdstate () & std::ios::failbit)
+                    //if (! is.eof () && is.rdstate () & std::ios::failbit)
+                    if (is.rdstate () & std::ios::failbit)
                       {
                         error (who, "format failed to match");
                         is.clear (is.rdstate () & (~std::ios::failbit));

But, this then causes a regression BIST to fail for bug #62723.

Overall, this is probably not too difficult to fix.  But, I think it means re-visiting bug #62723 and finding a different solution there.

This error happens because Octave is trying to parse "nan" and is detecting a conversion error (so only three values are returned) but failing to correctly set the error message.  You'll also see that the position is also not set correctly if you try

[val, count, msg, pos] = sscanf ('1 2 3 n', '%f')

This problem also happens if you replace 'n' with 'i', and you can also see what I think is a position error with '%d' in the following example:

octave> [val, count, msg, pos] = sscanf ('1 2 3 -', '%d')
val =

   1
   2
   3

count = 3
msg = sscanf: format failed to match
pos = 8

What does Matlab do for this case?