I have a code in which am trying to use outportb(), but while compiling it on MinGw i am getting below error.
C:\Users\A_TOMAR\AppData\Local\Temp\ccYPvctv.o:dsp.c:(.text+0x68): undefined reference to `outportb'
#include <stdio.h>
#include <stdlib.h>
#include <dos.h>
int main(void)
{
outportb(0x378,0xFF);
return 0;
}
I would like to know which header file is having this particular function?
Windows doesn't provide access to a hardware. You should use Win32 API calls.
This function is DOS specific and unavailable in Windows
Googling shows that your solution is inpout32.dll (example with weird font color)
#include <pc.h>
void outportb(unsigned short _port, unsigned char _data);
Related
My compiler (GCC) is giving me the warning:
warning: implicit declaration of function
Why is it coming?
You are using a function for which the compiler has not seen a declaration ("prototype") yet.
For example:
int main()
{
fun(2, "21"); /* The compiler has not seen the declaration. */
return 0;
}
int fun(int x, char *p)
{
/* ... */
}
You need to declare your function before main, like this, either directly or in a header:
int fun(int x, char *p);
The right way is to declare function prototype in header.
Example
main.h
#ifndef MAIN_H
#define MAIN_H
int some_main(const char *name);
#endif
main.c
#include "main.h"
int main()
{
some_main("Hello, World\n");
}
int some_main(const char *name)
{
printf("%s", name);
}
Alternative with one file (main.c)
static int some_main(const char *name);
int some_main(const char *name)
{
// do something
}
When you do your #includes in main.c, put the #include reference to the file that contains the referenced function at the top of the include list.
e.g. Say this is main.c and your referenced function is in "SSD1306_LCD.h"
#include "SSD1306_LCD.h"
#include "system.h" #include <stdio.h>
#include <stdlib.h>
#include <xc.h>
#include <string.h>
#include <math.h>
#include <libpic30.h> // http://microchip.wikidot.com/faq:74
#include <stdint.h>
#include <stdbool.h>
#include "GenericTypeDefs.h" // This has the 'BYTE' type definition
The above will not generate the "implicit declaration of function" error, but below will-
#include "system.h"
#include <stdio.h>
#include <stdlib.h>
#include <xc.h>
#include <string.h>
#include <math.h>
#include <libpic30.h> // http://microchip.wikidot.com/faq:74
#include <stdint.h>
#include <stdbool.h>
#include "GenericTypeDefs.h" // This has the 'BYTE' type definition
#include "SSD1306_LCD.h"
Exactly the same #include list, just different order.
Well, it did for me.
You need to declare the desired function before your main function:
#include <stdio.h>
int yourfunc(void);
int main(void) {
yourfunc();
}
When you get the error: implicit declaration of function it should also list the offending function. Often this error happens because of a forgotten or missing header file, so at the shell prompt you can type man 2 functionname and look at the SYNOPSIS section at the top, as this section will list any header files that need to be included. Or try http://linux.die.net/man/ This is the online man pages they are hyperlinked and easy to search.
Functions are often defined in the header files, including any required header files is often the answer. Like cnicutar said,
You are using a function for which the compiler has not seen a
declaration ("prototype") yet.
If you have the correct headers defined & are using a non GlibC library (such as Musl C) gcc will also throw error: implicit declaration of function when GNU extensions such as malloc_trim are encountered.
The solution is to wrap the extension & the header:
#if defined (__GLIBC__)
malloc_trim(0);
#endif
This error occurs because you are trying to use a function that the compiler does not understand. If the function you are trying to use is predefined in C language, just include a header file associated with the implicit function.
If it's not a predefined function then it's always a good practice to declare the function before the main function.
Don't forget, if any functions are called in your function, their prototypes must be situated above your function in the code. Otherwise, the compiler might not find them before it attempts to compile your function. This will generate the error in question.
The GNU C compiler is telling you that it can find that particular function name in the program scope. Try defining it as a private prototype function in your header file, and then import it into your main file.
I think the question is not 100% answered. I was searching for issue with missing typeof(), which is compile time directive.
Following links will shine light on the situation:
https://gcc.gnu.org/onlinedocs/gcc-5.3.0/gcc/Typeof.html
https://gcc.gnu.org/onlinedocs/gcc-5.3.0/gcc/Alternate-Keywords.html#Alternate-Keywords
as of conculsion try to use __typeof__() instead. Also gcc ... -Dtypeof=__typeof__ ... can help.
My compiler (GCC) is giving me the warning:
warning: implicit declaration of function
Why is it coming?
You are using a function for which the compiler has not seen a declaration ("prototype") yet.
For example:
int main()
{
fun(2, "21"); /* The compiler has not seen the declaration. */
return 0;
}
int fun(int x, char *p)
{
/* ... */
}
You need to declare your function before main, like this, either directly or in a header:
int fun(int x, char *p);
The right way is to declare function prototype in header.
Example
main.h
#ifndef MAIN_H
#define MAIN_H
int some_main(const char *name);
#endif
main.c
#include "main.h"
int main()
{
some_main("Hello, World\n");
}
int some_main(const char *name)
{
printf("%s", name);
}
Alternative with one file (main.c)
static int some_main(const char *name);
int some_main(const char *name)
{
// do something
}
When you do your #includes in main.c, put the #include reference to the file that contains the referenced function at the top of the include list.
e.g. Say this is main.c and your referenced function is in "SSD1306_LCD.h"
#include "SSD1306_LCD.h"
#include "system.h" #include <stdio.h>
#include <stdlib.h>
#include <xc.h>
#include <string.h>
#include <math.h>
#include <libpic30.h> // http://microchip.wikidot.com/faq:74
#include <stdint.h>
#include <stdbool.h>
#include "GenericTypeDefs.h" // This has the 'BYTE' type definition
The above will not generate the "implicit declaration of function" error, but below will-
#include "system.h"
#include <stdio.h>
#include <stdlib.h>
#include <xc.h>
#include <string.h>
#include <math.h>
#include <libpic30.h> // http://microchip.wikidot.com/faq:74
#include <stdint.h>
#include <stdbool.h>
#include "GenericTypeDefs.h" // This has the 'BYTE' type definition
#include "SSD1306_LCD.h"
Exactly the same #include list, just different order.
Well, it did for me.
You need to declare the desired function before your main function:
#include <stdio.h>
int yourfunc(void);
int main(void) {
yourfunc();
}
When you get the error: implicit declaration of function it should also list the offending function. Often this error happens because of a forgotten or missing header file, so at the shell prompt you can type man 2 functionname and look at the SYNOPSIS section at the top, as this section will list any header files that need to be included. Or try http://linux.die.net/man/ This is the online man pages they are hyperlinked and easy to search.
Functions are often defined in the header files, including any required header files is often the answer. Like cnicutar said,
You are using a function for which the compiler has not seen a
declaration ("prototype") yet.
If you have the correct headers defined & are using a non GlibC library (such as Musl C) gcc will also throw error: implicit declaration of function when GNU extensions such as malloc_trim are encountered.
The solution is to wrap the extension & the header:
#if defined (__GLIBC__)
malloc_trim(0);
#endif
This error occurs because you are trying to use a function that the compiler does not understand. If the function you are trying to use is predefined in C language, just include a header file associated with the implicit function.
If it's not a predefined function then it's always a good practice to declare the function before the main function.
Don't forget, if any functions are called in your function, their prototypes must be situated above your function in the code. Otherwise, the compiler might not find them before it attempts to compile your function. This will generate the error in question.
The GNU C compiler is telling you that it can find that particular function name in the program scope. Try defining it as a private prototype function in your header file, and then import it into your main file.
I think the question is not 100% answered. I was searching for issue with missing typeof(), which is compile time directive.
Following links will shine light on the situation:
https://gcc.gnu.org/onlinedocs/gcc-5.3.0/gcc/Typeof.html
https://gcc.gnu.org/onlinedocs/gcc-5.3.0/gcc/Alternate-Keywords.html#Alternate-Keywords
as of conculsion try to use __typeof__() instead. Also gcc ... -Dtypeof=__typeof__ ... can help.
Apologies for the dumb question. I checked all similar questions for the same error on stackoverflow, but it didn't help me understand why this error is happening in the following code.
I have one additional header file and a source file, which is included in the main file, and when I compile, I am getting the following error. I am trying to pass the char** argv from the main() to another function defined in another header file.
#include "include/Process.h"
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char** argv) {
if (argc < 2) {
printf("Please provide a path to file\n");
return (EXIT_FAILURE);
}
Process(argv);
Process.h:
#pragma once
extern void Process(char** path);
Process.c:
#include <stdio.h>
#include "../include/Process.h"
#include <stdlib.h>
#include <sys/stat.h>
#include <syslog.h>
#include <sys/types.h>
#include <unistd.h>
void Process(char** path) {
printf("%s\n", path[1]);
}
It gets compiled but the warning is
./src/Process.c:22:6: error: conflicting types for ‘Process’
void Process(char** path) {
^
./include/Process.h:17:6: note: previous declaration of ‘Process’ was here
extern void Process(char** path);
^
However, the warning disappears when I change the type of path from char** to char* and pass argv[1] instead of argv.
I am clueless why this is happening like this, and according to
this similar post, I tried adding a forward declaration for char** path above extern void Process(char** path); in the Process.h file, but it didn't help either.
Why is this error thrown when using char** path?
Why it disappears when I use char* path?
So far, I am able to see the program running, even with this warning. Is it safe to ignore this warning? If not, what could be the possible effects it can have during runtime?
Using gcc version 4.9.2 (Ubuntu 4.9.2-10ubuntu13)
Thanks.
Try putting your custom includes after the system includes.
It might be possible that the custom include defines a macro which interferes with the system includes. To minimize the risk of this, I always put the Standard C includes first, then any OS includes, and then third party libraries, and then my own ones
In theory the custom include shouldn't do this, and the system includes should only use reserved names, but in practice this doesn't always happen.
I have been able to remove almost all errors except these 5 errors in this C program (too long to paste so providing link).
http://codepad.org/AfqrDojN
The errors I receive are as follows:
I am using the following libraries:
#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <dos.h>
#include <conio.h>
What could be the issue?
you are redefining the function remove that is already declared in
#include <stdio.h>
changing the name of your function to (for example) void myremove() will probably solve your problem.
I was trying to set the timezone of my system, and was trying to use settimeofday(), which takes a timezone struct as an argument, but just read that that struct is now obsolete (http://linux.about.com/library/cmd/blcmdl2_settimeofday.htm) How could I go about doing this?
Thanks in advance.
EDIT: Ugh, I feel really stupid.
I created a link.c and compiled it:
#include <stdio.h>
void main()
{
printf("This is the link \n");
}
Created a target.c, and compiled it:
#include <stdio.h>
void main()
{
printf("This is the target \n");
}
and then tried the symlink function in a test program:
#include <unistd.h>
void main()
{
int garbage = symlink("/home/imandhan/pythonTests/link", "/home/imandhan/pythonTests/target");
printf(garbage);
}
This gives me a segmentation fault for some reason. Am I doing something wrong?
See tzset(3) for setting timezone for an application.
For the whole system - symlink /etc/localtime to appropriate file under /usr/share/zoneinfo/.