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[avr-gcc-list] c++ problems

From: Branislav Katreniak
Subject: [avr-gcc-list] c++ problems
Date: Thu, 21 Jul 2005 09:38:26 +0200
User-agent: Mutt/1.5.9i

Hi all,

I am trying to use C++ on the avr devices. I found it very usable, but I
have noticed several problems not mentioned in the FAQ. I am using
WinAVR 20050214.

- Constructors and destructors are twice in the .text section.
Code example:

class Test {
Test::Test()    { }
Test::~Test()   { }

Compiled code:

test.o:     file format elf32-avr

Disassembly of section .text:

00000000 <_ZN4TestC2Ev>:
class Test {
Test::Test()    { }
        0:      08 95           ret

00000002 <_ZN4TestC1Ev>:
        2:      08 95           ret

00000004 <_ZN4TestD2Ev>:
Test::~Test()   { }
        4:      08 95           ret

00000006 <_ZN4TestD1Ev>:
        6:      08 95           ret

When constructors and destructors get bigger, this eats much code space.
How can this be eliminated?

- Virtual tables (I suppose) are stored in RAM. 

This eats RAM memory but is no problem when virtual functions are not

- No support for pure virtual function.

No big problem, just to mention.

- I cannot get rid off this warning.

test.c:1: warning: alignment of 'TestVirtual::_ZTV11TestVirtual' is
greater than maximum object file alignment.  Using 1

What does it mean? It appears for every class with virtual functions.


Branislav Katreniak
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