Function works fine in MATLAB, however, when I get to MATLAB coder, it fails with error does not terminate due to an infinite loop

Hi all

I've got a function I've made in MATLAB, attached to this passage.

function [undistortedImage] = imwarpingImageFromFilenamesCoder(ImageFile,movingPoints,fixedPoints) %#codegen

fid  = fopen(movingPoints);
tline = fgetl(fid);
c = 2;
while(ischar(tline))
    tline = fgetl(fid);
    c = c + 1;
end
fclose(fid);

mP = zeros(c-2,2);

fid  = fopen(movingPoints);
s = fgetl(fid);
d = {','};
l = {};
while (length(s) > 0)
    [t,s] = strtok(s,d);
    l = {l{:}, t};
    l = string(l);
end
l = double(l);
mP(1,:) = l;

c = 2;
while(ischar(s))
    s = fgetl(fid);
    l = {};
    while (length(s) > 0)
        [t,s] = strtok(s,d);
        l = {l{:}, t};
        l = string(l);
    end
    mP(c,:) = double((l));
    c = c + 1;
end

movingPoints = mP(1:end-1,:);

mP = zeros(c-2,2);

fid  = fopen(fixedPoints);
s = fgetl(fid);
d = {','};
l = {};
while (length(s) > 0)
    [t,s] = strtok(s,d);
    l = {l{:}, t};
    l = string(l);
end
l = double(l);
mP(1,:) = l;
c = 2;
while(ischar(s))
    s = fgetl(fid);
    l = {};
    while (length(s) > 0)
        [t,s] = strtok(s,d);
        l = {l{:}, t};
        l = string(l);
    end
    mP(c,:) = double((l));
    c = c + 1;
end

fixedPoints = mP(1:end-1,:);

I = imread(ImageFile);
tform = fitgeotform2d(movingPoints,fixedPoints,"projective");
undistortedImage = imwarp(I,tform);

fclose(fid);

end

This function runs fine on MATLAB (sorry for how messy it is, I've been changing functions that don't work in coder with one's that do, such as readmatrix with fgetl, etc...). Now, though, it seems too run in coder (kind of) I get the source code in c, but I get an error that says this fx does not terminate due to an infinite loop. I went to the main c file, and there is indeed this line

  while (1) {
    fgetl(fid, c_fid);
  }
  

Which is an infinite loop, but I don't have any idea how the MATLAB code produces this line in C, and my C skill is not the strongest, so I'm struggling to figure out how I can fix it in C.

Answer 1

[Steven Lord]

Rather than checking if s is a char vector or has positive length, if you want to stop when the file has been read in I'd use feof instead. Or since you calculate how many lines the file has (the c variable) use that in a for loop instead of using while.

[Alexander Dumont]

Okay I will do that. Thank you for the help!