RE: gcc 3.4.2 + fpack-struct + hash_map

[Eljay Love-Jensen <eljay at adobe dot com>]

Hi Thierry,

>In our case, pack structures are used for network packet decoding and the choice was made to pack structure to make it simple and avoid errors.

Then if I were working on your QUICK-AND-DIRTY project, I'd instrument the code with the GCC __attribute__((packed)) on the network packet structures, and nothing else.  That would be the quick-and-dirty fix.

I stand by my earlier general advice to NOT pack those structures, and rather to make binary-format-savvy read/write routines.

But this is "quick and dirty".

>So actually, I am rather looking for a work-around (or some backward compatibility feature in gcc?).

You may need to rebuild the Standard C++ Library with pack turned on, since you are being indiscriminate with what is/isn't packed.

I presume you are using Intel based Linux, because other Linux platforms may or may not work with packed structures.

There is a non-trivial performance penalty with using packed structures, even on Intel architecture.

However, see next...

>Using the fpack-struct on this project would just be a way to get a running version of my program in short time (no code changes, no specific tests)..

I think that -fpack-struct will cause you more grief than my suggestion above to instrument the code's network packet structs.

>...and have my boss happy to migrate to the linux world ;-).

Can't argue with that.  :-)

Sincerely,
--Eljay