Question

如何在C中将一个指令定义为另一个指令？

ex：我要定义

#define #warning #warn

我收到错误

error #41: expected an identifier

例如，对于编译器和目标，某些编译器可识别#warning，而另一些则可识别#warn。

我已经有办法做到这一点，但我想使其通用化

#if PLATFORMS_TOOLCHAIN == PLATFORMS_ticgt
  #warn "RAM is not initialized at startup, test will possibly fail"
#else
  #warning "RAM is not initialized at startup, test will possibly fail"
#endif

Answer 1

无法创建自己的预处理程序指令。 <link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.1.1/css/bootstrap.css" rel="stylesheet"/> <div class="card"> <div class="card-body"> <div class="table-wrapper-2"> <table class="table table-striped table-bordered table-fixed" id="entityTable"> <thead> <tr class="table-primary sticky-top"> <th scope="col" style="width: 3%">#</th> <th scope="col" style="width: 19%">ID</th> <th scope="col" style="width:19%">Col 1</th> <th scope="col" style="width: 19%">Col 2</th> <th scope="col" style="width: 19%">Col 3</th> <th scope="col" style="width: 19%">Col 4</th> </tr> </thead> <tbody> <tr *ngFor="let id of transactionId, let i = index" class="clickable-row" (click)="onTransactionIdChange(id)"> <td>{{i+1}}</td> <td>{{id}}</td> <td>{{col1[i]}}</td> <td>{{col2[i]}}</td> <td>{{col3[i]}}</td> <td>{{col4[i]}}</td> </tr> <tr *ngFor="let id of transactionId, let i = index" class="clickable-row" (click)="onTransactionIdChange(id)"> <td>{{i+1}}</td> <td>{{id}}</td> <td>{{col1[i]}}</td> <td>{{col2[i]}}</td> <td>{{col3[i]}}</td> <td>{{col4[i]}}</td> </tr> <tr *ngFor="let id of transactionId, let i = index" class="clickable-row" (click)="onTransactionIdChange(id)"> <td>{{i+1}}</td> <td>{{id}}</td> <td>{{col1[i]}}</td> <td>{{col2[i]}}</td> <td>{{col3[i]}}</td> <td>{{col4[i]}}</td> </tr> <tr *ngFor="let id of transactionId, let i = index" class="clickable-row" (click)="onTransactionIdChange(id)"> <td>{{i+1}}</td> <td>{{id}}</td> <td>{{col1[i]}}</td> <td>{{col2[i]}}</td> <td>{{col3[i]}}</td> <td>{{col4[i]}}</td> </tr> <tr *ngFor="let id of transactionId, let i = index" class="clickable-row" (click)="onTransactionIdChange(id)"> <td>{{i+1}}</td> <td>{{id}}</td> <td>{{col1[i]}}</td> <td>{{col2[i]}}</td> <td>{{col3[i]}}</td> <td>{{col4[i]}}</td> </tr> <tr *ngFor="let id of transactionId, let i = index" class="clickable-row" (click)="onTransactionIdChange(id)"> <td>{{i+1}}</td> <td>{{id}}</td> <td>{{col1[i]}}</td> <td>{{col2[i]}}</td> <td>{{col3[i]}}</td> <td>{{col4[i]}}</td> </tr> <tr *ngFor="let id of transactionId, let i = index" class="clickable-row" (click)="onTransactionIdChange(id)"> <td>{{i+1}}</td> <td>{{id}}</td> <td>{{col1[i]}}</td> <td>{{col2[i]}}</td> <td>{{col3[i]}}</td> <td>{{col4[i]}}</td> </tr> <tr *ngFor="let id of transactionId, let i = index" class="clickable-row" (click)="onTransactionIdChange(id)"> <td>{{i+1}}</td> <td>{{id}}</td> <td>{{col1[i]}}</td> <td>{{col2[i]}}</td> <td>{{col3[i]}}</td> <td>{{col4[i]}}</td> </tr> <tr *ngFor="let id of transactionId, let i = index" class="clickable-row" (click)="onTransactionIdChange(id)"> <td>{{i+1}}</td> <td>{{id}}</td> <td>{{col1[i]}}</td> <td>{{col2[i]}}</td> <td>{{col3[i]}}</td> <td>{{col4[i]}}</td> </tr> <tr *ngFor="let id of transactionId, let i = index" class="clickable-row" (click)="onTransactionIdChange(id)"> <td>{{i+1}}</td> <td>{{id}}</td> <td>{{col1[i]}}</td> <td>{{col2[i]}}</td> <td>{{col3[i]}}</td> <td>{{col4[i]}}</td> </tr> <tr *ngFor="let id of transactionId, let i = index" class="clickable-row" (click)="onTransactionIdChange(id)"> <td>{{i+1}}</td> <td>{{id}}</td> <td>{{col1[i]}}</td> <td>{{col2[i]}}</td> <td>{{col3[i]}}</td> <td>{{col4[i]}}</td> </tr> </tbody> </table> </div> </div> </div>伪指令仅允许您定义新的源符号。

您当前正在做的是在不同的编译器上处理不同指令的正确方法。

Answer 2

通常这是不可能的，但是您可以使用#pragma有效地生成_Pragma keyword指令。

#define PRAGMA(...) _Pragma(#__VA_ARGS__)
PRAGMA(message "my message")
//as if you wrote: #pragma message "my message"

考虑到这一点，您的编译器可能具有一些编译指示，可让您模拟#warn或#error （#pragma GCC warning "message"或#pragma GCC error "message"）。

如果您的编译器没有这种编译指示，则总是可以通过扩展到相对上下文无关且不可编译的内容（例如char ERROR[-1];（负数组大小是非法的））来使编译失败。

如何在C中将一个指令定义为另一个指令？

2 个答案: