Getting error from: dlen = uint32(0) ; - matlab

Question

I don't know why but I am getting this error:
Error in mr_lsbpex (line 3)
dlen = uint32(0) ;
Output argument "a" (and maybe others) not assigned during call to "E:\path\mr_lsbpex.m>mr_lsbpex"
I have tested "dlen = uint32(0) ;" in matlab enviorment (outside of this function) and everything was OK. Here is my code:
function a = mr_lsbpex ( r, p )
% extract from an array
dlen = uint32(0) ;
s = size (r) ;
rnd = rand (s(1),s(2)) ;
rd = 32 ;
rl = s(2) ;
for i=1:s(2)
if rnd(1,i)<rd/rl
d = bitget (round(r(1,i)/p),1);
dlen = bitset (dlen,rd,d);
rd = rd -1 ;
end
rl = rl -1 ;
end
if (dlen > 10000000 )
clear a ;
return ;
end
a = uint8(zeros(dlen,1)) ;
rd = double(dlen * 8) ;
rl = double(s(1)*s(2)-s(2)) ;
for i=2:s(1)
for j=1:s(2)
if rnd(i,j)<rd/rl
d = bitget (round(r(i,j)/p) ,1) ;
a = z_set_bit (a,rd,d) ;
rd = rd - 1 ;
end
rl = rl - 1 ;
end
end

Answer 1

Remember: a needs to be returned ALLWAYS!
The error is not in that specific line, but in the "whole" function itself.
Your problem is that Matlab thinks that a its not going to be created. And actually in some case it may not be created.
The following line in the beginning of your function should do the trick
a=0; % well, or a=NaN; or whatever you want to return
Additionally, don't clear a in if (dlen > 10000000 ).