* [Bug c++/64232] Derived class with implicitly declared assignment operator is std::is_assignable though base class is not std::is_assignable
2014-12-09 1:53 [Bug c++/64232] New: Derived class with implicitly declared assignment operator is std::assignable though base class is not std::assignable mmehlich at semanticdesigns dot com
@ 2014-12-09 12:09 ` redi at gcc dot gnu.org
2014-12-09 21:49 ` mmehlich at semanticdesigns dot com
1 sibling, 0 replies; 3+ messages in thread
From: redi at gcc dot gnu.org @ 2014-12-09 12:09 UTC (permalink / raw)
To: gcc-bugs
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64232
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
std::is_assignable says:
"Only the validity of the immediate context of the assignment expression is
considered. [ Note: The compilation of the expression can result in side
effects such as the instantiation of class template specializations and
function template
specializations, the generation of implicitly-defined functions, and so on.
Such
side effects are not in the âimmediate contextâ and can result in the program
being ill-formed. â end note ]"
i.e. is_assignable isn't magic and can't give the right answer in all cases,
especially if you have members with nonsensical signatures.
>From gcc-bugs-return-469868-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Tue Dec 09 12:19:43 2014
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From: "wolfgang.roehrl@gi-de.com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/64236] New: Missing alignment
Date: Tue, 09 Dec 2014 12:19:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idd236
Bug ID: 64236
Summary: Missing alignment
Product: gcc
Version: 4.8.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: wolfgang.roehrl@gi-de.com
Hi,
I would like to post a bug report for the GNU C/C++ compiler 4.8.3.
We use the compiler to generate code for a PowerPC processor.
Invokation line for the GNU C++ compiler:
ccppc -c -x c++ -std=c++11 -Wall -Werror -g -mcpu
40 -meabi
-ftls-model=local-exec -msdata=sysv -fno-common -mspe -mabi=spe
-mfloat-gprs=double -mbig -mmultiple -mno-string -misel -mstrict-align
-fverbose-asm -fno-exceptions -fno-rtti -fgcse-sm -fno-section-anchors
-ftemplate-backtrace-limit -G 8 -O3
-I<some include paths>
-D<some #define's>
X.CPP -oX.O
// file X.CPP
#define SIZE_DATA_CACHE_BLOCK 32u
struct S
{ double d; };
struct alignas(sizeof(S)) S1
{ char d[sizeof(S)]; };
struct alignas(SIZE_DATA_CACHE_BLOCK) alignas(sizeof(S)) S2
{ char d[sizeof(S)]; };
alignas(S) char s1[sizeof(S)];
alignas(SIZE_DATA_CACHE_BLOCK) alignas(S) char s2[sizeof(S)];
S1 s3;
S2 s4;
An inspection of the generated assembler file (see below) shows the following
alignments:
. s1: alignment = 8
. s2: alignment = 32
. s3: alignment = 8
. s4: alignment = 8 ???
I think that s4 should also be aligned on a 32-byte boundary (C++11 standard,
7.6.2/4).
Following is the generated assembler file:
.globl s4
.section ".sbss","aw",@nobits
.align 3 <--- 8-byte alignment ???
s4:
.zero 8
.size s4, 8
.type s4, @object
.globl s3
.align 3 <--- 8-byte alignment
s3:
.zero 8
.size s3, 8
.type s3, @object
.globl s2
.align 5 <--- 32-byte alignment
s2:
.zero 8
.size s2, 8
.type s2, @object
.globl s1
.align 3 <--- 8-byte alignment
s1:
.zero 8
.size s1, 8
.type s1, @object
Kind regards
W. Roehrl
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