when i run coverity scan on python code (static code analysis), REVERSE_INULL and FORWARD_NULL error are detected. can anyone tell what is difference between REVERSE_INULL and FORWARD_NULL ? why these error are detected.
REVERSE_INULL means that you have a dereference followed by a null-type check.
In pseudo code
x := null
...
x.deref
...
if x is null
# handle null-type x
The fix would be to put the null-type check before the dereference.
FORWARD_NULL is simply where there is a path for a null-valued variable to be dereferenced. Another pseudo-code example
x := null
...
if x is null
print warning
# but x is still null
x.deref
Here you have to ensure that the null-ness is always handled.
So ultimately I'd say that REVERSE_INULL does the same null dereference checking as FORWARD_NULL but that it additionally detects a check after the dereference.
(standard disclaimer - I used to work for Synopsys, but not the division producing Coverity).
Related
I am using clingo to solve a homework problem and stumbled upon something I can't explain:
normalized(0,0).
normalized(A,1) :-
A != 0.
normalized(10).
In my opinion, normalized should be 0 when the first parameter is 0 or 1 in every other case.
Running clingo on that, however, produces the following:
test.pl:2:1-3:12: error: unsafe variables in:
normalized(A,1):-[#inc_base];A!=0.
test.pl:2:12-13: note: 'A' is unsafe
Why is A unsafe here?
According to Programming with CLINGO
Some error messages say that the program
has “unsafe variables.” Such a message usually indicates that the head of one of
the rules includes a variable that does not occur in its body; stable models of such
programs may be infinite.
But in this example A is present in the body.
Will clingo produce an infinite set consisting of answers for all numbers here?
I tried adding number(_) around the first parameter and pattern matching on it to avoid this situation but with the same result:
normalized(number(0),0).
normalized(A,1) :-
A=number(B),
B != 0.
normalized(number(10)).
How would I write normalized properly?
With "variables occuring in the body" actually means in a positive literal in the body. I can recommend the official guide: https://github.com/potassco/guide/releases/
The second thing, ASP is not prolog. Your rules get grounded, i.e. each first order variable is replaced with its domain. In your case A has no domain.
What would be the expected outcome of your program ?
normalized(12351,1).
normalized(my_mom,1).
would all be valid replacements for A so you create an infinite program. This is why 'A' has to be bounded by a domain. For example:
dom(a). dom(b). dom(c). dom(100).
normalized(0,0).
normalized(A,1) :- dom(A).
would produce
normalize(0,0).
normalize(a,1).
normalize(b,1).
normalize(c,1).
normalize(100,1).
Also note that there is no such thing as number/1. ASP is a typefree language.
Also,
normalized(10).
is a different predicate with only one parameter, I do not know how this will fit in your program.
Maybe your are looking for something like this:
dom(1..100).
normalize(0,0).
normalize(X,1) :- dom(X).
foo(43).
bar(Y) :- normalize(X,Y), foo(X).
I got some account issues in the SCN so I make a attempt here.
We switched to Unicode and got some issues with that. INFTY_TAB = PS+2. This coding gets an error that "the offset + length is exceeding".
I found some hints but couldn't really figure out how to fix this. And even when I manage to fix those errors I got a new error called 'Iclude-Report %HR_P9002 not found'. The IT is still there so is there something else I can check?
Definition of PS:
DATA: BEGIN OF PS OCCURS 0.
*This indicates if a record was read with disabled authority check.
data: authc_disabled(1) type c.
DATA: TCLAS LIKE PSPAR-TCLAS.
INCLUDE STRUCTURE PRELP.
DATA: ACRCD LIKE SY-SUBRC.
DATA: END OF PS.
TCLAS is a char(1) field.
This is the part where the error pops up:
INFTY_TAB = PS+2.
Error: I had to translate so sorry for some mistakes that could appear.
Offset and Length (=2432) exceed the length of the character based beginning (=2430) of the structure.
Depends on the length of INFTY_TAB. You have to explicitly set length:
INFTY_TAB = PS+2(length).
Official information is here. The important point to note is that the inclusion of SY-SUBRC (which is an INT4 field) places a limit to the range of fields you can access using this (discouraged) method of access.
ASSIGN field+off TO is generally forbidden from a syntactical
point of view since any offset <> 0 would cause the range to be
exceeded.
Although the sentence above is related to ASSIGN command, it is also valid for this situation.
I wrote a procedure which imports data from an xml-file into a MariaDB using library DBI. The procedure works but I don't understand why the following code gives me the message:
use of uninitialized value $DBI::err in concatenation (.) or string at ...
Here the code (abbreviated):
my $insert_art = $dbh->prepare(
"INSERT INTO odbb_articles (creation_dt,ref_data,comp_no)".
"VALUES (?,?,?)"
);
....
my $comp_no = $xpc->findvalue('./sr:ARTCOMP/sr:COMPNO',$node1);
....
$insert_art->execute($creation_dt,$ref_data,$comp_no)
or die "Fehler bei der Ausfuehrung: ".
"$DBI::err -> $DBI::errstr (odbb_articles $DBI::state)\n";
If I insert the code
if ($comp_no eq "") { $comp_no = undef; }
just before $insert_art->execute the procedure works. This error happens when there is no entry in the xml-file for element COMPNO. I can avoid it if I define it as undef. I just wonder
why $comp_no cause this problem and
is there another solution than to control if $comp_no is "" and define it as undef?
The reason for the second question is to avoid the if statement if there are a lot of variables/columns which may have empty entries.
Thanks for help.
use of uninitialized value $DBI::err in concatenation (.) or string at ...
The error message you are seeing is Perl telling you that $DBI::err is undef. That is not because of the value of your $comp_no. It's just a result of what your program is doing.
So when you pass an empty string to the comp_no column, the database doesn't like that. It throws an error. DBI catches that error and passes it on. The $insert_art->execute returns a false value and the right-hand-side of the or gets called. That's your die.
Now in the string that you pass to die you put three variables:
$DBI::err
$DBI::errstr
$DBI::state
According to the DBI documentation, those are equivalent to the functions $h->err, $h->errstr and $h->state with $h being the last handle used. Let's look at the docs for those.
$h->err
Returns the native database engine error code from the last driver method called. The code is typically an integer but you should not assume that.
The DBI resets $h->err to undef before almost all DBI method calls, so the value only has a short lifespan. Also, for most drivers, the statement handles share the same error variable as the parent database handle, so calling a method on one handle may reset the error on the related handles. [...]
This does not explain when it can be undef.
$h->errstr
Returns the native database engine error message from the last DBI method called. This has the same lifespan issues as the "err" method described above.
The returned string may contain multiple messages separated by newline characters.
The errstr() method should not be used to test for errors, use err() for that, because drivers may return 'success with information' or warning messages via errstr() for methods that have not 'failed'.
Ok, so this is text. Don't use it to test for specific errors. You're not doing that. You just want to give debug output when the program fails.
$h->state
Returns a state code in the standard SQLSTATE five character format. Note that the specific success code 00000 is translated to any empty string (false). If the driver does not support SQLSTATE (and most don't), then state() will return S1000 (General Error) for all errors.
The driver is free to return any value via state, e.g., warning codes, even if it has not declared an error by returning a true value via the "err" method described above.
The state() method should not be used to test for errors, use err() for that, because drivers may return a 'success with information' or warning state code via state() for methods that have not 'failed'.
Again, this is not very clear about how useful it is.
My advice is to get rid of $DBI::err and $DBI::state. You don't need those to figure out what the problem is. Just output $DBI::errstr.
$insert_art->execute($creation_dt,$ref_data,$comp_no)
or die "Fehler bei der Ausfuehrung: " . $dbh->errstr;
Now your program will still fail, but at least you will have a meaningful error message that will explain what your database didn't like about the statement. That's better than being told how there is a bug in your error handling code.
Afterwards, the other answers will probably apply to fix the reason this is happening in the first case.
On another note, a word on die: If you provide a \n at the end of your arguments, it will not print your current script, line number and input handle line number. But those might be useful in your case. You can include them.
In a SQL database an empty string is very different to null.
If comp_no has a foreign key pointing to a record in another table, then the value "" is an accettable one only if there is a record with "" as primary key, very improbable.
Yu can fix this converting empty values to undef:
for ($creation_dt,$ref_data,$comp_no ){
defined $_ and $_ eq '' and $_ = undef;
}
$insert_art->execute($creation_dt,$ref_data,$comp_no);
or also
$insert_art->execute(map {defined($_) && length($_) ? $_ : undef} ($creation_dt,$ref_data,$comp_no));
This is a possible shortcut:
$comp_no ||= undef;
With the caveat that this will work in any case where $comp_no evaluates as false, meaning a value of 0 will actually cause the result to go undef also, which may or may not matter to you. If your field is numeric, I'd say it matters a lot.
I have written this function, and I have already defined values for rg and Lp, but still when I run this function it returns the error : (Input argument "Lr" is undefined.
Error in ==> Bis at 12
if f(Lr,rg,Xo)*f(Lr,rg,Xf)>0)
here is the function :
function[Lp,Xo,Xf]=Bis(Lr,rg)
Xo=0;
Xf=10;
Err=0.01;
syms x;
f=inline('(sqrt((2/3)*(((x*Lr)/3)-(x*x)+((2*x*x*x)/Lr)-((2*x*x*x*x)/(Lr*Lr))+(((2*x*x*x*x)/(Lr*Lr))*exp(-Lr/x))))-rg)');
if f(Lr,rg,Xo)*f(Lr,rg,Xf)>0
disp('The values you entered are not apropriate !')
PlotLpFunction;
Lp='unknown';
elseif f(Lr,rg,Xo)*f(Lr,rg,Xf)==0
if f(Lr,rg,Xo)==0
Lp=Xo;
elseif f(Lr,rg,Xf)==0
Lp=Xf;
end
elseif f(Lr,rg,Xo)*f(Lr,rg,Xf)<0
xi=(Xf-Xo)/2;
while abs(f(Lr,rg,xi))>Err
if f(Lr,rg,xi)*f(Lr,rg,Xf)<0
Xo=xi;
xi=(Xo+Xf)/2;
elseif f(Lr,rg,xi)*f(Lr,rg,Xf)>0
Xf=xi;
xi=(Xo+Xf)/2;
end
end
Lp=xi;
end
The code executes for me on the newest version of Matlab, other than the fact that I don't have the PlotLpFunction.
My initial impression was that you forgot to send the Lr (and all other argument) into you're inlined f function, very easy to fix by adding them as arguments to the inline function. You'll find the full usage in the official documentation.
The relevant part being
inline(expr,arg1,arg2,...) constructs an inline function whose input
arguments are specified by the strings arg1, arg2,.... Multicharacter
symbol names may be used.
but it seems to form the inline just fine by itself on both Matlab 2011b and 2008b, from context presumably. Answer is accepted now, so presumably that was the problem. Can anyone else reproduce his problem? If so please provide your Matlab version or other circumstances.
So far from what I have read this error can be caused by confusing or redundant naming within the program but I don't think that is the issue here since everything is declared clearly. From what I can see in this my issue is coming from the declaration of piecewise that is then being run through integration below and therefor the program is attempting to access a array cell that doesn't exist. If this is the case I have so far been stumped at how to fix this issue. Any assistance with this problem would be greatly appreciated.
syms t k n
fct = #(t)evalin(symengine,['subs(piecewise([0 <= t and t < 2,',...
'sin((Pi*t^2)/4)],[t <= 2 and t < 3, 5*t-t^2-6], [t <=3 and t < 4, 0],',...
'[Otherwise, t-4]),t=',regexprep(mat2str(x),' ',','),')']);
evalin(symengine,'assume(k,Type::Integer)');
a = #(fct,t,k) int(fct*cos(k*pi*t/4)/4,t,-2,8);
b = #(fct,t,k) int(fct*sin(k*pi*t/4)/4,t,-2,8);
FourierSeries = #(fct,t,n) a(fct,t,0)/4 + ...
symsum(a(fct,t,k)*cos(k*pi*t/4) + b(fct,t,k)*sin(k*pi*t/4),k,1,n);
pretty(FourierSeries(t,25,1))
ezplot(FourierSeries(t,25,1),-2,8)
hold on
ezplot(fct,-2,8)
hold off
title('Partial sum with n=25')
The complete error text is as follows:
??? Attempt to reference field of non-structure array.
Error in ==> sym.int at 56
r = mupadmex('symobj::intdef',f.s,x.s,a.s,b.s);
Error in ==> #(fct,t,k)int(fct*cos(k*pi*t/4)/4,t,-2,8)
Error in ==>
#(fct,t,n)a(fct,t,0)/4+symsum(a(fct,t,k)*cos(k*pi*t/4)+b(fct,t,k)*sin(k*pi*t/4),k,1,n)
Error in ==> FourierProgram at 16 pretty(FourierSeries(t,25,1))
This was asked long ago, but I'll provide an answer since one was never given.
As your error indicates, the issue is with this line and how the anonymous function a is called:
a = #(fct,t,k) int(fct*cos(k*pi*t/4)/4,t,-2,8);
The sym/int function expects the second argument (the variable with which the integration is performed with respect to) to be a symbolic variable. However, you're calling FourierSeries(t,25,1), which passes the value 25 as the integration variable.
This bit of code should replicate the issue in your version of Matlab (back in 2011 when this was asked):
syms t k;
int(t*cos(k*pi*t/4)/4,25,-2,8)
However, in R2015a I now get a different (and a bit clearer) error message:
Cannot integrate with respect to ''. The integration variable must be a symbolic variable.