Why i am getting this error message
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function pushbutton1_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
clc
s =str2double(get(handles.edit1,'string'));
in =str2double(get(handles.edit2,'string'));
en =str2double(get(handles.edit3,'string'));
t=s:in:en;
y=eval(get(handles.edit4,'string')); %line 181
figure(1)
plot(t,y)
title('Actual graph')
x=0;
y1 = zeros(1,(length(t)-1));
for i=1:(length(t)-1)
x=x+(y(1,i+1)*in);
y1(1,i)=x;
end
t1=s:in:(en-in);
figure(2)
plot(t1,y1)
title('After Intregation')
1 个评论
Christopher Wallace
2018-7-25
What is on line 181?
Please reformat the code in the question. It isn't possible to see where the lines end.
采纳的回答
OCDER
2018-7-25
The error you're getting is probably caused by an invalid/empty string in handles.edit4. And DON'T use eval, esepecially in a GUI's editable text!
y = eval('')
Error: This statement is incomplete.
y = eval(get(handles.edit4,'string')); %DON'T USE EVAL! Security Risk!
% What if handles.edit4.string = 'delete(every_file)' ? You'll lose a lot of files!
What are you "evaluating"? Give us an example and we'll provide a safer and faster alternative to eval.
8 个评论
Robiul Ferdous
2018-7-25
Walter Roberson
2018-7-25
str2func() instead of eval() . This still leaves security risks though, so ideally you should validate that the expression is well formed and not a risk before you str2func()
Try something like this instead of that eval line.
FullStr = get(handles.edit4, 'string'); %EX: sin(2*pi*t)
FuncStr = FullStr(1:find(FullStr == '(', 1)-1);
SafeStr = {'sin', 'cos', 'tan'}; %Select function names you are okay with
if ~ismember(FuncStr, SafeStr)
fprintf('"%s" is not a valid function. These are: ', FuncStr);
fprintf(' "%s" ', SafeStr{:});
fprintf('\n');
return %ends your callback function early
end
FuncHdl = str2func(['@(t) ' FullStr]);
try
y = FuncHdl(t);
catch
disp('Something is wrong with this function handle:')
disp(FuncHdl);
return
end
Walter Roberson
2018-7-25
编辑：Walter Roberson
2018-7-25
Perhaps
FuncStrs = regexp(FullStr, '\w+(?=\()', 'match');
if ~all(ismember(FuncStrs, SafeStr))
as this should allow for a mix of functions such as sin(3*x)-cos(x/pi)
Thanks Walter, that's much more robust. And here's one more security check, in case someone uses a string like:
FullStr = 'sin(mkdir(''test''),t)'; %Sneaky security bypass
and if you cannot list every safe string possible.
UnsafeStr = {'delete', 'rmdir', 'mkdir', 'movefile', 'copyfile'};
if contains(FullStr, UnsafeStr)
fprintf('Detected an unsafe string! Cannot have: \n');
fprintf(' "%s" ', UnsafeStr{:});
fprintf('\n');
return
end
There might be safer ways...
Walter Roberson
2018-7-25
My suggestion already handles the nested calls
The rule for computer security is to never count on blacklists, as someone might find a clever way of encoding around the blacklist. For example systems that checked input text for ` specifically often failed to check percent encoding %60 or unicode %u0060 or HTML entities `
OCDER
2018-7-25
I see. This clears up the blacklist vs whitelist approach. The other issue was what if the whitelist wasn't so obvious or is large? EX:
tanh(t) + sech(t) + ... more trig func
One way to get a larger whitelist would be:
SafeStr = arrayfun(@(x) strrep(x.name, '.m', ''), dir(fullfile(ctfroot, 'toolbox', 'matlab', 'elfun', '*.m')), 'un', 0)
Now more functions for trig are valid.
Walter Roberson
2018-7-25
Interesting approach.
Though this does accidentally bring in the script 'Contents' (which is effectively just a help file script.)
更多回答（1 个）
Robiul Ferdous
2018-7-26
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1 个评论
OCDER
2018-7-26
The Answer is reserved for answer to your original question. If this is a new error and new question, post a new question. Otherwise, no one will try to respond here as an Answer was already accepted.
Post full error message in you new question post. Read this:
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