All functions are implicitly extern, yes, but there's sometimes more to be said.
Code:
// To use a C function from C++ you must warn the linker to expect
// the symbol _functionname, not a C++ hashed overload like @kldsgjlakgjadls
extern "C" int functionname(int);
Also different linking specifications for different kinds of libraries, i.e. so's and dll's vs statically linked things. Sometimes the linker can handle that for you, but it's often more efficient, at least, to warn it in advance that it will be calling external library code.
Hi,
Please let me know if the extern keyword is necessary for using functions which is defined and declared in another file and and used in a different file where both these files are linked together.
thanks (8 Replies)
Hi ,
I have three funcions f1, f2 and f3 .
f1 calls f2 and f2 calls f3 .
I have a global variable "period" which i want to pass to f3 .
Can i pass the variable directly in the definition of f3 ?
Pls help .
sars (4 Replies)
Hi there, I'm having a bit of a strange problem which I would appreciate some help with.
The Problem:
I have two external hard drives, but I'm borrowing one off my parents to copy data too (one of mine, which is identical to theirs - WD MyBook 300g - is on its way out).
Fedora 9 recognizes... (3 Replies)
Hi,
I'm searching for an solution for the following problem.
I want fetch some mails via pop3 from a@a.com with fetchmail.
That works perfectly. Now any incoming mail should forwarded to b@b.com via smtp obv. But I don't know how to configure that. All online tutorials describe forwarding to... (0 Replies)
Why this is happening when both of them compiled together and run?
I am getting segmentation fault SIGSEGV.
File1.c:
int arr;
File2.c:
extern int *arr;
int main() {
arr = 100;
} (3 Replies)
In the header file data.h i got:
const char ack_msg = "ack: received your msg\n";
In the code file server.c i got:
extern const char ack_msg;
And else it is only used in a function call:
user$ grep ack_msg *c *h
server.c:extern const char ack_msg;
server.c: n = write(clientsfd,... (5 Replies)
Dear All.
I have a script, which process files one by one. In the script I have two functions.
one sftp files to different server
the other from existing file create file with different name.
My question is:
Will sftp function recognize files names , which are created in another... (1 Reply)
Hi All,
Good Day, seeking for your assistance on how to not perform my 2nd, 3rd,4th etc.. function if my 1st function is in else condition.
#Body
function1()
{
if
then
echo "exist"
else
echo "not exist"
}
#if not exist in function1 my all other function will not proceed.... (4 Replies)
Discussion started by: meister29
4 Replies
LEARN ABOUT MOJAVE
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