Re: strange timing behaviour

["Yann E. MORIN" <yann dot morin dot 1998 at anciens dot enib dot fr>]

Hell Amir!
All,

On Wednesday 22 July 2009 09:56:03 Amir Tsvitov wrote:
> The toolchain worked great until just recently when we discovered that
> when we move a certain function around to different files in the source
> tree we get large delays (~few milli seconds) between the call to the
> function and its execution.? When the function is placed in some files
> there is no problem while in other files there is the large delay.

And what's your program doing in the meantime: is it running, or is
it sleeping?

Then try to run it through gdb and stop just prior to calling the function.
Then, look where it's jumping to: is it your function's body, or some other
code?

If it's jumping elsewhere, then try to find where that code comes from.
Maybe it's some C++ handling for whatever runtime.

If it's directly to your function's body, what's going on next? Is it
directly executing your code, or calling soem preamble (ie another call)?

Also, how is your program linked? Are all your object files linked
together, or are you building shared libraries with some of them? If
you're building shared libs, then is your function going into one of
them instead of the main executable?

> This only happen when we compile with g++, with gcc there is no problem
> (our code is pure C but for various reasons we are required to compile
> it with g++)
> Any ideas as to what could be causing this and how to further investigate
> it?

For one, I'd try to relax the requirement for g++ if you're doing pure C
and gcc does work. It smells like C++ runtime overhead, to me...

Regards,
Yann E. MORIN.

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