[enter link description here][1]I am writing this program which will enabled conditional compilation.
When the program is compiled in a standard way like this, it works fine without any error message:
gcc -Werror -Wall -pedantic -ansi -g -c display.c -o displayStack
But when I would like to compile with conditional compilation, I have an error message saying that there are implicit declaration of my functions in display.c
Here is how i compile it:
gcc -Werror -Wall -pedantic -ansi -g -c display.c -o displayStack -D STACK
Here is how I wrote the conditional command in the code:
#ifdef STACK
printLinkedList( stack );
#endif
Here is the stack.h file showing the include of LinkedList.h which has the function prototype for printLinkedList.
#ifndef STACK
#define STACK
#include "LinkedList.h"
LinkedList *createStack();
void push( LinkedList *, void * );
void *top( LinkedList * );
void *pop( LinkedList * );
void freeStack( LinkedList * );
#endif
May I know is there any issue over here? I cannot seem to find the problem because the first statement was working perfectly but when I have added "-D STACK" the program just show error message. Is it something wrong with my compiling command?
Error message I am receiving:
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
The files can be find in the folder here. [1]: https://github.com/Calmen00-code/BracketCheck
The problem is the include guard in the stack.h file:
#ifndef STACK
When you then define STACK on the command line that condition becomes FALSE and the header contents are not included. This results in missing prototypes in the C file.
To fix this you need to change either the C files or the header file to use a different preprocessor variable.