Re: object file memory

Kaz Kylheku wrote, On 2/6/2012 5:07 PM:
On 2012-02-06, Bill M<wpmccormick@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
I have an object file foo.o that I want to link to an executable. The
main executable creates a number of child threads that use code and
variables from foo.o.

Do you have the source code for foo.o that you can tweak and recompile?
Yes

I've included a very simplistic representation at
the end. My question is, how can each child thread (worker) get it's own
private copy of global variables foo_char and foo_int? Or does that just
happen auto-magically?

Why would that happen automagically? It's completely the wrong thing which
would break most programs.

** foo.c **
char foo_char;
int foo_int;

These are static variables, which are understood to be single-instance,
and any correct program relies on them being that way. Automagically making
these thread-local would be broken behavior.

GCC has extensions for declaring statics thread local. Check the GCC
documentation for the setion on "Thread-Local Storage", but the gist of it is:

__thread char foo_char;

There is also an explicit POSIX API for managing thread-specific values
accessed by keys: pthread_key_create, pthread_setspecific, etc.

So I just started reading about keys (after my original post here) and I was hoping for something even easier. The GCC thread local extensions seem pretty simple to implement. I give that a try first.

Thanks!!
.

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