变量具有不完整的类型'struct my_error_mgr'

当我尝试构建此代码时，该行struct my_error_mgr jerr;显示错误“变量的类型不完整'struct my_error_mgr'

#import "Engine.h"
#include "jpeglib.h"

@implementation Engine
+(void)test{
    struct jpeg_decompress_struct cinfo;
    struct my_error_mgr jerr;
    FILE * infile;

    if ((infile = fopen(filename, "rb")) == NULL) {
        fprintf(stderr, "can't open %s\n", filename);
        return 0;
    }

    cinfo.err = jpeg_std_error(&jerr.pub);
    jerr.pub.error_exit = my_error_exit;

    if (setjmp(jerr.setjmp_buffer)) {
        jpeg_destroy_decompress(&cinfo);
        fclose(infile);
        return 0;
    }

    jpeg_create_decompress(&cinfo);

    jpeg_stdio_src(&cinfo, infile);

    (void) jpeg_read_header(&cinfo, TRUE);

    jvirt_barray_ptr* coeffs_array;
    coeffs_array = jpeg_read_coefficients(&cinfo);

    BOOL done = FALSE;
    for (int ci = 0; ci < 3; ci++)
    {
        JBLOCKARRAY buffer_one;
        JCOEFPTR blockptr_one;
        jpeg_component_info* compptr_one;
        compptr_one = cinfo.comp_info + ci;

        for (int by = 0; by < compptr_one->height_in_blocks; by++)
        {
            buffer_one = (cinfo.mem->access_virt_barray)((j_common_ptr)&cinfo, coeffs_array[ci], by, (JDIMENSION)1, FALSE);

            for (int bx = 0; bx < compptr_one->width_in_blocks; bx++)
            {
                blockptr_one = buffer_one[0][bx];

                for (int bi = 0; bi < 64; bi++)
                {
                    blockptr_one[bi]++;
                }                  
            }   
        } 
    }

    write_jpeg(output, &cinfo, coeffs_array); // saving modified JPEG to the output file

    jpeg_destroy_decompress(&cinfo);
    fclose(infile);
}
@end

当我尝试注释掉与此错误相关的所有EXC_BAD_ACCESS行时，然后在该行上出现运行时错误

(void) jpeg_read_header(&cinfo, infile);

我试图修改iOS中已保存JPEG图像的DCT系数，最终目标是创建JPEG隐写应用程序。我有以下代码尝试向每个DCT系数加一个。我正在使用libjpeg库。该代码是Objective-C和C的组合。

快速说明，变量文件名等于“ / Users / ScottBouloutian / Library / Application Support / iPhone Simulator / 7.0.3 / Applications / 27A0450​​E-4685-4C3E-AAC8-A0CC6C85359E / Crypsis.app / screen.jpg”是我要修改的JPEG图像的路径。

我的代码有什么问题？这是愚蠢的，例如缺少包含项还是我的文件路径有问题？