Yalantis/uCrop · error · CImgArgumentException

"[" cimg_appname "_math_parser] CImg<

Error message

"[" cimg_appname "_math_parser] CImg<%s>: Function 'da_remove()': Dynamic array is empty."

What it means

mp_da_remove() throws this when the dynamic array is valid but has zero elements (stored element count siz==0), so there is nothing to remove. Removing from an empty dynamic array is treated as an invalid operation rather than a no-op.

Solutions

  1. Check da_size(#ind)>0 before calling da_remove.
  2. Restructure loops to stop when the array is empty.
  3. Re-populate the array with da_insert if it should contain elements at this point.

Example fix

// before
 da_remove(#0,0)
// after
 if (da_size(#0)>0, da_remove(#0,0), 0)
Defensive patterns

Strategy: validation

Validate before calling

// Only remove when the array has elements
if (da_size(ind) > 0) { remove(ind, start, end); }

Type guard

function isNonEmptyDa(img) { return Boolean(img) && img.counter > 0; }

Try / catch

try { evalMath(expr); } catch (e) { if (String(e).includes('Dynamic array is empty')) { skipOrRepopulate(); } else throw e; }

Prevention

When it happens

Trigger: Calling da_remove() on an image whose element counter is 0 — typically after all elements were already removed by previous da_remove calls, or the array was initialized but never filled.

Common situations: Loops that pop elements without checking emptiness; scripts that drain a queue/stack stored in a dynamic array; re-running a script on already-processed images.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

AI-assisted analysis of Yalantis/uCrop@f788b534b4 (2026-09-08). Data as JSON: /api/errors/1666c0e83418b55f. Report an issue: GitHub.

Appendix: source

Thrown at ucrop/src/main/jni/CImg.h:26407

              }
          }
        img[img._height - 1] = (T)cimg::uint2float(siz + nb_elts);
        return cimg::type<double>::nan();
      }

      static double mp_da_remove(_cimg_math_parser& mp) {
        mp_check_list(mp,"da_remove");
        const unsigned int ind = (unsigned int)cimg::mod((int)_mp_arg(2),mp.imglist.width());
        CImg<T> &img = mp.imglist[ind];
        int siz = img?(int)cimg::float2uint((float)img[img._height - 1]):0;
        if (img && (img._width!=1 || img._depth!=1 || siz<0 || siz>img.height() - 1))
          throw CImgArgumentException("[" cimg_appname "_math_parser] CImg<%s>: Function 'da_remove()': "
                                      "Specified image #%u of size (%d,%d,%d,%d) cannot be used as dynamic array%s.",
                                      mp.imgout.pixel_type(),ind,
                                      img.width(),img.height(),img.depth(),img.spectrum(),
                                      img._width==1 && img._depth==1?"":" (contains invalid element counter)");
        if (!siz)
          throw CImgArgumentException("[" cimg_appname "_math_parser] CImg<%s>: Function 'da_remove()': "
                                      "Dynamic array is empty.",
                                      mp.imgout.pixel_type());
        int
          start0 = mp.opcode[3]==~0U?siz - 1:_mp_arg(3),
          end0 = mp.opcode[4]==~0U?start0:_mp_arg(4),
          start = start0<0?start0 + siz:start0,
          end = end0<0?end0 + siz:end0;
        if (start<0 || start>=siz || end<0 || end>=siz || start>end)
          throw CImgArgumentException("[" cimg_appname "_math_parser] CImg<%s>: Function 'da_remove()': "
                                      "Invalid starting (%d) and ending (%d) positions "
                                      "(not ordered, in range -%d...%d).",
                                      mp.imgout.pixel_type(),start0,end0,siz,siz - 1);
        if (end<siz - 1) // Move remaining data in dynamic array
          cimg_forC(img,c) std::memmove(img.data(0,start,0,c),img.data(0,end + 1,0,c),(siz - 1 - end)*sizeof(T));
        siz-=end - start + 1;
        if (img.height()>32 && siz<img.height()/8) // Reduce size of dynamic array
          img.resize(1,std::max(2*siz + 1,32),1,-100,0);
        img[img._height - 1] = (T)cimg::uint2float(siz);

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