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POC: Different type declaration by casting void pointer in a function
 

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  1. POC: Different type declaration by casting void pointer in a function
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    <p>The following <code>insertSNode</code> function inserts <code>item</code> and <code>return</code>s updated pointer. Within the <code>insertSnode</code> function, each data from different <code>struct</code> is dereferenced accordingly.</p> <p><strong>PROBLEM:</strong> I get compiler errors on <strong>(LINE 1), (LINE 2), (LINE 3), (LINE 4)</strong> with the following error message:</p> <blockquote> <p>"Member reference base type 'void' is not a structure or union."</p> </blockquote> <p><strong>QUESTION:</strong></p> <p>How do I get rid of compiler errors? If I can't, alternatively, do we have any better solution in writing functions as much identical as this situation? Let's assume there are too many <code>struct</code> types (i.e. Type_A, Type_B, etc), and it is extremely inefficient to create different functions with different type declarations.</p> <pre><code>*pListTypeA = (Type_A *) insertSnode(*pListTypeA, pPreTypeA, pTypeAItem, TYPEA); *pListTypeB = (Type_B *) insertSnode(*pListTypeB, pPreTypeB, pTypeBItem, TYPEB); *pListTypeC = (Type_C *) insertSnode(*pListTypeC, pPreTypeC, pTypeCItem, TYPEC); // more assignments </code></pre> <p><code>insertSnode</code> definition:</p> <pre><code>void* insertSnode(void* pList, void* pPre, char* item, const int type) { void *pNew; if (TYPEA == type) { pList = (Type_A*) pList; pPre = (Type_A*) pPre; pNew = (Type_A*) pNew; } else if (TYPEB == type) { pList = (Type_B*) pList; pPre = (Type_B*) pPre; pNew = (Type_B*) pNew; } else (TYPEC == type) { pList = (Type_C*) pList; pPre = (Type_C*) pPre; pNew = (Type_C*) pNew; } if (!(pNew = malloc(sizeof(*pList)))) { printf(ERR_NOT_ENOUGH_MEMORY); exit(EXIT_NOT_ENOUGH_MEMORY); } pNew-&gt;name = item; // compiler error: (LINE 1) if (pPre == NULL) { pNew-&gt;link = pList; // compiler error: (LINE 2) pList = pNew; } else { pNew-&gt;link = pPre-&gt;link; // compiler error: (LINE 3) pPre-&gt;link = pNew; // compiler error: (LINE 4) } return pList; } </code></pre> <p><strong>NOTE:</strong> </p> <p>FYI: I was able to run this code with no if-statements for type-declarations and just one type (e.g. Type_A). So, we all know there are no external problems than the type-declarations.</p>
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    1. USJ. Berman
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    1. COQuite frankly I believe you are better off with a dedicated function per type - even if it is more verbose. The approach you are taking will make your `insertSNode` function to become larger and larger and more unmaintainable with time. Maybe you should instead reconsider having so many lists?
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      1. USAnders K.
 

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