read some book on C C program must have main() function to run. With this statement
Code:
main;
you define a symbol with name "main". Both link and compiler require this symbol and you defined it. That's why compilation and linkage works. But when you start the compiled program it tries to call the function with the name "main". It finds the symbol main in the symbol table and makes jump to the symbol definition. But because you didn't define the symbol as function it is unpredictable what is now held in the memory under the symbol main. Hopefully nulls. As result you receive core dumped, because kernel can't execute nulls or finds no instruction to execute.
When you write "unix" instead of "main", you didn't define "main" symbol and the program can't be compiled without main.
i just finished a project for a c++ class that i wrote at home on my computer, compiled with gcc. when i brought the code into school it would not compile, it would complain that cannot call main() function. at school we use ancient borland c++ from 1995. anyway my program has 20 different... (3 Replies)
Hi,
I have a main loop which calls a sub loop, which finally returns to the main loop itself. The main loop runs when a flag is set. Now, I have a signal handler for SIGINT, which resets the flag and thus stops the main loop. Suppose I send SIGINT while the program is in subloop, I get an error... (1 Reply)
Hi! I've a C program as shown below..
The line numbers and the statements of the program are separated by a space..
1 #include<stdio.h>
2 char a,b,c;
3 float x,y,z;
4 int main()
5 {
6 int d,e,f;
7 // further declarations
8 // further declarations
9 /* body*/
10 }
11 void fun1()
12... (1 Reply)
why does this not work?
#include <stdio.h>
#include <stdlib.h>
char getFileMode(char charChanger) {
char filetype; /*var to hold the value to be returned*/
filetype = charSetter; /*set filetype to "l" if it is a symlink*/
return filetype;
}
int main(void){
char... (8 Replies)
Hi friends,
when I am passing arguments to main, I want another function to be able to have access to that function, the problem is that I am creating athread, which has a function like void *xyz(void *), how can pass the refernce of argv to this function, if you see my program, you will better... (2 Replies)
H friends,
As we know, a function returns a value and that value is saved somwhere. like
int Sum( int x, int y )
{
return x + y;
}
Total = Sum( 10, 20 );
The value 30 is saved in variable Total.
Now the question is, what int value does the function main return, and where is it... (5 Replies)
Hello All,
I am trying to call a function from the calling main program from a dlopened library function, below is the entire code, when I execute it it crashes with sigill. Can you guys help me out I guess I am missing out on the linker flag or something here. besides I am new to AIX and... (1 Reply)
I feel that i am missing something obvious but i can't find what is wrong.
I have a script that is launching some functions with "&" and each call is feeding the array with a value. When all calls are finished I just want to retrieve the values of that array.
It is looking like that :
... (5 Replies)
Hi. I have some code, that for some reason, I could not post it here in this post. Here's the address for it:
#if 0 shc Version 4.0.1, Generic Shell Script Compiler GNU GPL Version 3 Md - Pastebin.com
First off, I used "shc" to convert the code from shell script to C.
And The... (6 Replies)
Discussion started by: ignatius
6 Replies
LEARN ABOUT OSX
dlsym
DLSYM(3) BSD Library Functions Manual DLSYM(3)NAME
dlsym -- get address of a symbol
SYNOPSIS
#include <dlfcn.h>
void*
dlsym(void* handle, const char* symbol);
DESCRIPTION
dlsym() returns the address of the code or data location specified by the null-terminated character string symbol. Which libraries and bun-
dles are searched depends on the handle parameter.
If dlsym() is called with a handle, returned by dlopen() then only that image and any libraries it depends on are searched for symbol.
If dlsym() is called with the special handle RTLD_DEFAULT, then all mach-o images in the process (except those loaded with dlopen(xxx,
RTLD_LOCAL)) are searched in the order they were loaded. This can be a costly search and should be avoided.
If dlsym() is called with the special handle RTLD_NEXT, then dyld searches for the symbol in the dylibs the calling image linked against when
built. It is usually used when you intentionally have multiply defined symbol across images and want to find the "next" definition. It
searches other images for the definition that the caller would be using if it did not have a definition. The exact search algorithm depends
on whether the caller's image was linked -flat_namespace or -twolevel_namespace. For flat linked images, the search starts in the load
ordered list of all images, in the image right after the caller's image. For two-level images, the search simulates how the static linker
would have searched for the symbol when linking the caller's image.
If dlsym() is called with the special handle RTLD_SELF, then the search for the symbol starts with the image that called dlsym(). If it is
not found, the search continues as if RTLD_NEXT was used.
If dlsym() is called with the special handle RTLD_MAIN_ONLY, then it only searches for symbol in the main executable.
RETURN VALUES
The dlsym() function returns a null pointer if the symbol cannot be found, and sets an error condition which may be queried with dlerror().
NOTES
The symbol name passed to dlsym() is the name used in C source code. For example to find the address of function foo(), you would pass "foo"
as the symbol name. This is unlike the older dyld APIs which required a leading underscore. If you looking up a C++ symbol, you need to use
the mangled C++ symbol name.
SEE ALSO dlopen(3)dlerror(3)dyld(3)ld(1)cc(1)
August 28, 2008
08-03-2015
C program must have main() function to run. With this statement