I am following along a tutorial for C programming in 6502 Assembly and am having a great deal of difficulty on the 3rd step. When compiling my code in the command line, i get these errors:
test4.c(8): Error: '{' expected
test4.c(9): Warning: Function must be extern
test4.c(9): Error: ';' expected
test4.c(13): Error: '}' expected
I am using a program to compile .c files made in code::blocks to .nes files. The current tutorial is having me also make .s assembly file when compiling in the cl65 command line in Windows from the program that is compiling it. Here is the link to the tutorial page i am on:
https://helloacm.com/tutorial-3-c-programming-in-6502-using-assembly/
I have tried many different combinations of code that i can think of to try and get rid of a least some of the problems, but alas to no avail. I am an amateur in C, usually use C++ but i cannot and still trying to figure this out. I was not able to find the "Function must be extern" error anywhere with a quick google search either. Anyone have an idea what's going on?
Here is how i wrote the code in code::blocks:
void main()
{
asm("nop");
}
void testasm()
void main()
{
while(1) {
testasm(); // call the assembled function
}
}
Also, had a really difficult time following along on this particular tutorial part.
Thanks in advance, any help is appreciated on diagnosing the problem!
Perhaps this is what you're after?
void testasm()
{
asm("nop");
}
void main()
{
while(1) {
testasm(); // call the assembled function
}
}
Your code had two main() functions, and a prototype void testasm() with no terminating semicolon.
Alternatively, if testasm is written in assembly, your code should look like this (removing the extra main function):
extern void testasm(); // `extern` not specifically required, but may be for
// your particular compiler
void main()
{
while(1) {
testasm(); // call the assembled function
}
}
You need to be much more careful writing code.
Related
I am trying to instrument the linux kernel code to insert a function call in every function right after a BitCast instruction.
So I modify the C code to #include <linux/my_header.h> where I have my printer function.
The header looks something like this.
#ifndef __header_ID
#define __header_ID
static inline void print_typecast(...){
printk(...);
}
#endif
Then I use Xclang to load my FunctionPass, which looks something like this.
// M is of type llvm::Module*
Function* f = M->getFunction("print_typecast");
if (f == nullptr) {
errs() << "Function not found in the module\n";
}
else {
// insert function in the code
}
However, my pass never finds the function in the module. When I remove the static it will find the function but then the linker in the final compilation step will complain of duplicate definition.
Anyone knows how to make LLVM "see" static imported/included functions?
Edit: I have also gone to the extreme where I have the same function directly written in every c file of the kernel code (the ones that #include <linux/kernel.h>)
static means that all calls to this function will be visible to this compiller now, and by implication that if the compiler sees no such calls, then it can skip compiling any output for the function, because you as programmer have promised that noone will want it.
I'm writing a simple code in C language, and this works.
Which compiles and excutes with no errors, gives the expected output.
#include <stdio.h>
int main(void) {
struct SiteTemplate {
int views;
};
int visit(struct SiteTemplate *site) {
site -> views++;
return 0;
}
struct SiteTemplate site;
site.views = 0;
visit(&site);
printf("%d\n", site.views);
return 0;
}
But in my VS Code, with C_Cpp linting is on, my IDE shows the following error and other problems with it.
declaration is incompatible with previous "visit" (declared at line 8)
Having a screenshot of it:
This error linting is really confusing me since my code works with gcc, it doesn't show any error when compiling.
And also, if I move my struct and function definition to the global level instead of inside main(), then the errors don't exist anymore... But what's the error declaration is incompatible? Or is there any problem with my code?
Click here to view the another screenshot to save whitespaces of this page.
By the way, the version of my VS Code is 1.52.0, with default C_Cpp linting.
Nested function definition is not standard C, it's supported by compiler extensions. According to C standard, any function definition needs to appear outside of any other function definition.
[I've been looking at other questions and none of the solutions have worked so I'll ask my own question.
I'm working on a Ubuntu Kylin16.04(China version) and having trouble compiling my code, here are my gets function, the error received by the compiler]1
Implicit declaration of function means that you don't have function reference somewhere in header file normally.
Or maybe you have it, but the file where your function is called does not see this.
//Declaration, must always be before first function call
void myfunc(void);
//Function usage somewhere in the code
int main(void) {
//Call it here, compiler see the reference and knows what type
//of func it is and what parameters should be used to func
myfunc();
}
//Definition, write function content here
//This part will be compiled in separate way, linked will put everything together
void myfunc(void) {
//Write function content here
}
I work at a motor programm (and i have to control multiple motors thats why i use the struct) together with my arduino MEGA.
I dont't understand why MOTOR is out of scope when I use it as argument in the drive function:
typedef struct motor
{
int EN;
/*some more ints*/
}MOTOR;
MOTOR mot1;
MOTOR mot2; /*this works with no compile error*/
int drive (MOTOR*) /*here i have compile error out of scope, neither with or without pointer*/
{
return 1;
}
void setup()
{}
void loop()
{}
sketch_jul25a:2: error: 'MOTOR' was not declared in this scope
sketch_jul25a:2: error: expected primary-expression before ')' token
sketch_jul25a.ino: In function 'int drive(MOTOR*)':
sketch_jul25a:9: error: 'int drive(MOTOR*)' redeclared as different kind of symbol
sketch_jul25a:2: error: previous declaration of 'int drive'
'MOTOR' was not declared in this scope
Because the road to hell is paved with good intentions.
The Arduino IDE tries to be helpful by generating prototypes for all user-defined functions at the beginning of the code. When one of these prototypes references a user-defined type, things blow up in the manner described.
The trick is to make the code unparseable by the IDE:
namespace
{
int drive (MOTOR*)
{
return 1;
}
}
The IDE runs into namespace and has no idea what to do with the block that follows, so skips it.
And i suggest this should do the job as good as the namespace option?
struct motor
{
int EN;
/*some more ints*/
};
int drive (motor* mtr);
motor mot1;
motor mot2; /*this works with no compile error*/
int drive (motor* mtr)
{
return 1;
}
void setup()
{}
void loop()
{
int a = drive(&mot1);
}
EDIT: My original answer made some assumptions that Arduino IDE was closer to AVR-GCC than it actually was. My general recommendation for anyone who is familiar with C or C++ that is doing a lot of work with these chips is to use Atmel studio and AVR-GCC directly as you will run into less issues this way.
Arduino is actually C++ underneath but it does some preprocessing before it turns your code into the C++ code that gets compiled for the chip (like creating main from setup and loop). The issue you have is due to a preprocessing step and is explained by Ignacio Vazquez-Abrams' answer.
As a more general c++ usage note I'd recommend changing your struct definition to this:
struct motor
{
int EN;
/*some more ints*/
};
You might want to read Difference between 'struct' and 'typedef struct' in C++? to see why things are a bit different in c++.
For a very specific project, I need to write a 16-bit program in C and I'm using Microsoft QuickC in MS-DOS to write this program. Now I'm pretty sure the syntax of my program is correct but the program just won't compile and it thinks I have syntax errors. Is this because C-compilers in MS-DOS using an older version of C with different syntax?
#include<stdio.h>
main()
{
printf("Hello World!");
}
Not even that simple hello world program will compile and run.
you should define main as int
so change your code to :
int main() { // define main as an int returning function
// your code
return 0; // Also make sure you have return statement in main
}
and it will compile
Here is what it says in the standards:
1 The function called at program startup is named main. The implementation declares no prototype for this function. It shall be defined with a return type of int :
int main(void) { /* ... */ }
Edit:
Ok from your comments .. you are now getting this error:
C1024: cannot open include file 'stdio.h'
Here is a cause and solution from microsoft:
http://support.microsoft.com/kb/97809
You can't omit the type of the function main, or any other C function, for that matter. So, you want
void main() { ... }
or
int main(int argc, char **argv) { ... }
although with the latter one the compiler will usually require you to return a value.