Simulink中bwboundaries代码生成报错，如何修改代码解决？

问题背景 #

已在Simulation Target>Advanced中启用动态内存分配，默认阈值设为0，运行以下MATLAB代码时触发错误：

B={{nan}};    %%Defining so that it can be set as size variable.
coder.varsize('B',[50 1]);   
B={B;bwboundaries(BW,'noholes')}  %%Not B{:}=bwboundaries() as multiple inputs are not allowed
Y=B{2}                         
boundary=Y{2}

错误信息 #

=== Simulation (Elapsed: 1:21 min) ===
    Error:Simulink does not have enough information to determine output sizes for this block. If you think the errors below are inaccurate, try specifying types for the block inputs and/or sizes for the block outputs.
    Error:This assignment writes a 'cell' value into a 'double' type in element '{1}{1}'. Code generation does not support changing types through assignment. Check preceding assignments or input type specifications for type mismatches.
    
    Function 'Image Processing System/corner_detection' (#95.612.613), line 21, column 1:
    "B"
    Launch diagnostic report.
    Error:Errors occurred during parsing of MATLAB function 'flightControlSystem/Image Processing System/corner_detection'
    Error:Simulink cannot determine sizes and/or types of the outputs for block 'flightControlSystem/Image Processing System/corner_detection' due to errors in the block body, or limitations of the underlying analysis. The errors might be inaccurate. Fix the indicated errors, or explicitly specify sizes and/or types for all block outputs.
    Error:Simulink cannot determine sizes and/or types of the outputs for block 'flightControlSystem/Image Processing System/corner_detection' due to errors in the block body, or limitations of the underlying analysis. The errors might be inaccurate. Fix the indicated errors, or explicitly specify sizes and/or types for all block outputs.

解决方案 #

错误核心是嵌套cell与普通cell的类型不匹配：原代码初始化B={{nan}}为嵌套cell（cell内包含cell），后续拼接bwboundaries返回的普通cell数组时，导致元素类型冲突，代码生成不允许这种类型变更。修改步骤如下：

1. 直接初始化B为普通cell数组，无需嵌套结构
2. 保留coder.varsize声明以支持动态大小
3. 直接赋值bwboundaries的结果到B，避免不必要的拼接
4. 添加边界检查，防止索引越界

修改后的代码：

% 初始化B为普通cell数组，匹配bwboundaries返回的坐标类型
B = {[]};
% 声明B为动态大小的cell数组，最大尺寸[50 1]
coder.varsize('B', [50 1]);
% 直接将bwboundaries的结果赋值给B
B = bwboundaries(BW, 'noholes');
% 提取第二个边界（添加检查避免索引越界）
if length(B) >= 2
    boundary = B{2};
else
    boundary = [];
end

关键说明 #

• 去掉嵌套cell初始化，彻底解决类型冲突问题：bwboundaries返回的是存储坐标数组的cell数组，直接赋值即可
• 添加边界检查，符合代码生成的严谨性要求，避免运行时索引错误
• 保留coder.varsize声明，确保Simulink识别动态内存分配需求

内容的提问来源于stack exchange，提问作者space_monkey