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[Bug c++/37715] New: Different class sizes with public/private and alignments
- From: "adam at os dot inf dot tu-dresden dot de" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 2 Oct 2008 09:09:34 -0000
- Subject: [Bug c++/37715] New: Different class sizes with public/private and alignments
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
I've been experiencing some (for me) rather unexpected behavior with some C++
code. The following is a very reduced test case:
class A
{ private: void *one;
} __attribute__((aligned(16)));
class C {};
class L { public: class M : A { C _c; }; M m; };
L x;
It's about the size of L::M. I.e. if this file is compiled, L::M has a sizeof
of 16. If the first private is changed to public, the size of L::M changes to
32 (-Dprivate=public). Is this expected behavior? When removing the alignment
contraints, the size of L::M is 8 in both cases.
I'm seeing this behavior with all gcc versions tested (3.3, 3.4, 4.1, 4.2, 4.3,
head) as well as with different target architectures (i386, x86_64, arm).
This is the script use to show the difference:
#! /bin/sh
echo 'print sizeof(L::M)' > x.cmd
echo -n "orig: "
gcc -Wall -g -c x.cc
gdb -x x.cmd -batch x.o
echo -n "with define: "
gcc -Dprivate=public -Wall -g -c x.cc
gdb -x x.cmd -batch x.o
Thanks
--
Summary: Different class sizes with public/private and alignments
Product: gcc
Version: 4.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: adam at os dot inf dot tu-dresden dot de
GCC build triplet: i486-linux-gnu
GCC host triplet: i486-linux-gnu
GCC target triplet: i486-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37715