[在此处输入链接描述][1]我正在编写这个程序，它将启用条件编译。
当程序以这样的标准方式编译时，它可以正常工作，没有任何错误消息：
gcc -Werror -Wall -pedantic -ansi -g -c display.c -o displayStack
但是当我想使用条件编译进行编译时，我收到一条错误消息，指出在 display.c 中隐式声明了我的函数
这是我如何编译它：
gcc -Werror -Wall -pedantic -ansi -g -c display.c -o displayStack -D STACK
以下是我在代码中编写条件命令的方式：
#ifdef STACK
printLinkedList( stack );
#endif
这是显示包含LinkedList.h的stack.h文件，其中包含printLinkedList的功能原型。
#ifndef STACK
#define STACK
#include "LinkedList.h"
LinkedList *createStack();
void push( LinkedList *, void * );
void *top( LinkedList * );
void *pop( LinkedList * );
void freeStack( LinkedList * );
#endif
我可以知道这里有任何问题吗？我似乎找不到问题，因为第一条语句运行良好，但是当我添加"-D STACK"时，程序只会显示错误消息。我的编译命令有问题吗？
我收到的错误消息：
display.c: In function ‘display’:
display.c:21:5: error: unknown type name ‘LinkedList’
21 | LinkedList *stack = NULL;
| ^~~~~~~~~~
display.c:22:13: error: implicit declaration of function ‘createStack’ [-Werror=implicit-function-declaration]
22 | stack = createStack();
| ^~~~~~~~~~~
display.c:22:11: error: assignment to ‘int *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
22 | stack = createStack();
| ^
display.c:47:21: error: implicit declaration of function ‘push’ [-Werror=implicit-function-declaration]
47 | push( stack, bracket );
| ^~~~
display.c:52:30: error: request for member ‘head’ in something not a structure or union
52 | if( stack->head != NULL )
| ^~
display.c:54:38: error: implicit declaration of function ‘top’ [-Werror=implicit-function-declaration]
54 | popBracket = top( stack );
| ^~~
display.c:54:36: error: assignment to ‘char *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
54 | popBracket = top( stack );
| ^
display.c:72:42: error: implicit declaration of function ‘pop’ [-Werror=implicit-function-declaration]
72 | popBracket = pop( stack );
| ^~~
display.c:72:40: error: assignment to ‘char *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
72 | popBracket = pop( stack );
| ^
display.c:108:17: error: implicit declaration of function ‘printLinkedList’ [-Werror=implicit-function-declaration]
108 | printLinkedList( stack );
| ^~~~~~~~~~~~~~~
display.c:147:22: error: request for member ‘head’ in something not a structure or union
147 | if( stack->head == NULL ) /* Good case */
| ^~
display.c:151:28: error: assignment to ‘char *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
151 | popBracket = top( stack );
| ^
display.c:164:5: error: implicit declaration of function ‘freeStack’ [-Werror=implicit-function-declaration]
164 | freeStack( stack );
| ^~~~~~~~~
cc1: all warnings being treated as errors
calmen@calmen:~/Desktop/Project/BracketCheck$ vim display.h
calmen@calmen:~/Desktop/Project/BracketCheck$ gcc -Werror -Wall -pedantic -ansi -g -c display.c -o displayStack -D STACK
display.c: In function ‘display’:
display.c:21:5: error: unknown type name ‘LinkedList’
21 | LinkedList *stack = NULL;
| ^~~~~~~~~~
display.c:22:13: error: implicit declaration of function ‘createStack’ [-Werror=implicit-function-declaration]
22 | stack = createStack();
| ^~~~~~~~~~~
display.c:22:11: error: assignment to ‘int *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
22 | stack = createStack();
| ^
display.c:47:21: error: implicit declaration of function ‘push’ [-Werror=implicit-function-declaration]
47 | push( stack, bracket );
| ^~~~
display.c:52:30: error: request for member ‘head’ in something not a structure or union
52 | if( stack->head != NULL )
| ^~
display.c:54:38: error: implicit declaration of function ‘top’ [-Werror=implicit-function-declaration]
54 | popBracket = top( stack );
| ^~~
display.c:54:36: error: assignment to ‘char *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
54 | popBracket = top( stack );
| ^
display.c:72:42: error: implicit declaration of function ‘pop’ [-Werror=implicit-function-declaration]
72 | popBracket = pop( stack );
| ^~~
display.c:72:40: error: assignment to ‘char *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
72 | popBracket = pop( stack );
| ^
display.c:108:17: error: implicit declaration of function ‘printLinkedList’ [-Werror=implicit-function-declaration]
108 | printLinkedList( stack );
| ^~~~~~~~~~~~~~~
display.c:147:22: error: request for member ‘head’ in something not a structure or union
147 | if( stack->head == NULL ) /* Good case */
| ^~
display.c:151:28: error: assignment to ‘char *’ from ‘int’ makes pointer from integer without a cast [-Werror=int-conversion]
151 | popBracket = top( stack );
| ^
display.c:164:5: error: implicit declaration of function ‘freeStack’ [-Werror=implicit-function-declaration]
164 | freeStack( stack );
| ^~~~~~~~~
cc1: all warnings being treated as errors
这些文件可以在此处的文件夹中找到。 [1]： https://github.com/Calmen00-code/BracketCheck
问题是stack.h文件中的包含保护：
#ifndef STACK
然后，在命令行上定义STACK时，该条件变为 FALSE，并且不包括标头内容。这会导致 C 文件中缺少原型。
要解决此问题，您需要更改 C 文件或头文件以使用不同的预处理器变量。
gcc -Werror -Wall -pedantic -ansi -g -c display.c -o displayStack -D STACK
很奇怪。我会删除-D和STACK之间的空格
您可能有兴趣将-Wextra -fanalyze添加到gcc命令中。阅读有关调用 GCC 的章节、有关静态分析器选项的部分，并在 2020 年底考虑升级到 GCC 10。
此外，-ansi指的是旧的 C 标准。阅读 n1570 和现代 C，然后考虑使用-std=c11
当编译你的代码BracketCheck.tar.gz(md5sum1b81b34f26db85fef69bda62a5bd4e63)时，我得到make CFLAGS='-Wall -Wextra -g -std=c11'：
display.c: In function ‘display’:
display.c:21:5: error: unknown type name ‘LinkedList’
21 | LinkedList *stack = NULL;
| ^~~~~~~~~~
display.c:22:13: warning: implicit declaration of function ‘createStack’ [-Wimplicit-function-declaration]
22 | stack = createStack();
| ^~~~~~~~~~~
display.c:22:11: warning: assignment to ‘int *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
22 | stack = createStack();
| ^
display.c:47:21: warning: implicit declaration of function ‘push’ [-Wimplicit-function-declaration]
47 | push( stack, bracket );
| ^~~~
display.c:52:30: error: request for member ‘head’ in something not a structure or union
52 | if( stack->head != NULL )
| ^~
display.c:54:38: warning: implicit declaration of function ‘top’ [-Wimplicit-function-declaration]
54 | popBracket = top( stack );
| ^~~
display.c:54:36: warning: assignment to ‘char *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
54 | popBracket = top( stack );
| ^
display.c:72:42: warning: implicit declaration of function ‘pop’ [-Wimplicit-function-declaration]
72 | popBracket = pop( stack );
| ^~~
display.c:72:40: warning: assignment to ‘char *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
72 | popBracket = pop( stack );
| ^
display.c:108:17: warning: implicit declaration of function ‘printLinkedList’ [-Wimplicit-function-declaration]
108 | printLinkedList( stack );
| ^~~~~~~~~~~~~~~
display.c:147:22: error: request for member ‘head’ in something not a structure or union
147 | if( stack->head == NULL ) /* Good case */
| ^~
display.c:151:28: warning: assignment to ‘char *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
151 | popBracket = top( stack );
| ^
display.c:164:5: warning: implicit declaration of function ‘freeStack’ [-Wimplicit-function-declaration]
164 | freeStack( stack );
这是在带有GCC 10.2的Linux/x86-64/Ubuntu 20.04上。
我建议修复您的代码，直到您完全没有收到任何警告。
添加-DSTACK并不能修复所有错误。一旦它们都固定了，请使用 GDB 来了解程序的行为。
您可能会对这份报告草案以及资助它的解码器和战车项目感兴趣。
您也可以尝试在代码上使用 Frama-C 或 Clang 静态分析器。注意赖斯定理。
在阅读了Dragon这本书之后，你可以考虑使用GNU autoconf和/或GNU bison和/或ANTLR和/或GPP来生成一些代码(C，或你的makefile...)。