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c++/10645: Incorrect 64bit double alignment in nested struct
- From: jingye at ca dot ibm dot com
- To: gcc-gnats at gcc dot gnu dot org
- Date: 6 May 2003 19:15:18 -0000
- Subject: c++/10645: Incorrect 64bit double alignment in nested struct
- Reply-to: jingye at ca dot ibm dot com
>Number: 10645
>Category: c++
>Synopsis: Incorrect 64bit double alignment in nested struct
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: unassigned
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Tue May 06 19:16:01 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator: jingye@ca.ibm.com
>Release: gcc version 3.2
>Organization:
>Environment:
System Type:
Linux Version 2.4.19 SuSE SLES 8 (ppc) - Kernel 2.4.19-ul1-ppc64-SMP (36).
GNU assembler version 2.12.90.0.15 (powerpc-suse-linux) using BFD version 2.12.9
0.0.15 20020717 (SuSE)
Configured with: ../configure --enable-threads=posix --prefix=/usr --with-local-
prefix=/usr/local --infodir=/usr/share/info --mandir=/usr/share/man --libdir=/us
r/lib --enable-languages=c,c++,f77,objc,java,ada --enable-libgcj --with-gxx-incl
ude-dir=/usr/include/g++ --with-slibdir=/lib --with-system-zlib --enable-shared
--enable-__cxa_atexit powerpc-suse-linux
Thread model: posix
gcc version 3.2
>Description:
in the example below, the struct A has only double as its member and is 8-byte aligned in 64bit. struct B has struct A as it's member, however, is only 4-byte aligned. When we add aother member after double in struct A, struct B becomes 8-byte aligned.
/*test case t.c*/
struct A{
double a1;
/*int a2;*/
}sa;
struct B{
char b1;
struct A b2;
}sb;
int main()
{
printf("alignof sa=%d\n",__alignof__(sa));
printf("sizeof sa=%d\n",sizeof(sa));
printf("alignof sb=%d\n",__alignof__(sb));
printf("sizeof sb=%d\n",sizeof(sb));
}
>How-To-Repeat:
/opt/cross/bin/powerpc64-linux-g++ t.c
a.out
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted: