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* [Bug c++/12222] New: explicit initialization of static template members seems ignored
@ 2003-09-09 10:16 stefaandr at hotmail dot com
2003-09-09 14:08 ` [Bug c++/12222] " bangerth at dealii dot org
` (4 more replies)
0 siblings, 5 replies; 7+ messages in thread
From: stefaandr at hotmail dot com @ 2003-09-09 10:16 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12222
Summary: explicit initialization of static template members seems
ignored
Product: gcc
Version: 3.4
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: stefaandr at hotmail dot com
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
Shouldn't this code output 1234? It outputs 0 for me. I used to write
b a<float>::b1 instead of template <> b a<float>::b1, but
I tried this after seeing comment 3 on bug 11930. I can even
change the constructor of b into a non-default one and it still compiles...
using g++-3.4 (GCC) 3.4 20030907 (experimental)
#include <iostream>
struct b {
b() { m = 1234; }; int m;
};
template <class T>
struct a { static b b1; };
template struct a<float>;
template <> b a<float>::b1;
int main() {
std::cout << a<float>::b1.m << std::endl;
};
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/12222] explicit initialization of static template members seems ignored
2003-09-09 10:16 [Bug c++/12222] New: explicit initialization of static template members seems ignored stefaandr at hotmail dot com
@ 2003-09-09 14:08 ` bangerth at dealii dot org
2003-09-09 17:53 ` stefaandr at hotmail dot com
` (3 subsequent siblings)
4 siblings, 0 replies; 7+ messages in thread
From: bangerth at dealii dot org @ 2003-09-09 14:08 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12222
bangerth at dealii dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed| |1
Last reconfirmed|0000-00-00 00:00:00 |2003-09-09 14:08:31
date| |
------- Additional Comments From bangerth at dealii dot org 2003-09-09 14:08 -------
Your code is invalid: you have the explicit instantiation before the declaration
of an explicit specialization of the member. That confuses the compiler. If you
revert the order, you get this error message:
tmp/g> ../build-gcc/gcc-install/bin/c++ x.cc -W -Wall
/tmp/ccQIMlpO.o(.text+0x11): In function `main':
: undefined reference to `a<float>::b1'
collect2: ld returned 1 exit status
That is due to the fact that you only _declare_ the existence of an explicit specialization,
not define it. If instead of
template <> b a<float>::b1;
you write
template <> b a<float>::b1 = b();
then the code compiles properly and yields the expected result.
Now, this is indeed confusing -- gcc should be able to issue a warning about specializing
after instantiating. Besides, there is kind of a bug anyway: when accessing
a<float>::b1.m, gcc is apparently presently using the static member from the general
template, not the specialization. That's fine, because the code is invalid. However, it
is equally apparently not initializing it properly, since otherwise we would get the
right answer.
W.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/12222] explicit initialization of static template members seems ignored
2003-09-09 10:16 [Bug c++/12222] New: explicit initialization of static template members seems ignored stefaandr at hotmail dot com
2003-09-09 14:08 ` [Bug c++/12222] " bangerth at dealii dot org
@ 2003-09-09 17:53 ` stefaandr at hotmail dot com
2003-09-09 18:57 ` bangerth at dealii dot org
` (2 subsequent siblings)
4 siblings, 0 replies; 7+ messages in thread
From: stefaandr at hotmail dot com @ 2003-09-09 17:53 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12222
------- Additional Comments From stefaandr at hotmail dot com 2003-09-09 17:53 -------
Appearantly, if I do a specialized initialization
template <> b a<float>::b1 = b();
and a templated one
template <class T> b a<T>::b1 = b();
over different object files, the result of the linking is that the same object
(same this pointer) is initialized twice (seen by std-outing something inside
the constructor). Is this a bug in the linker or the compiler?
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/12222] explicit initialization of static template members seems ignored
2003-09-09 10:16 [Bug c++/12222] New: explicit initialization of static template members seems ignored stefaandr at hotmail dot com
2003-09-09 14:08 ` [Bug c++/12222] " bangerth at dealii dot org
2003-09-09 17:53 ` stefaandr at hotmail dot com
@ 2003-09-09 18:57 ` bangerth at dealii dot org
2003-12-26 23:36 ` pinskia at gcc dot gnu dot org
2004-08-16 18:37 ` bangerth at dealii dot org
4 siblings, 0 replies; 7+ messages in thread
From: bangerth at dealii dot org @ 2003-09-09 18:57 UTC (permalink / raw)
To: gcc-bugs
PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12222
------- Additional Comments From bangerth at dealii dot org 2003-09-09 18:57 -------
That's your problem -- declaring an explicit specialization in a place where the
compiler can't see it invokes undefined behavior.
W.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/12222] explicit initialization of static template members seems ignored
2003-09-09 10:16 [Bug c++/12222] New: explicit initialization of static template members seems ignored stefaandr at hotmail dot com
` (2 preceding siblings ...)
2003-09-09 18:57 ` bangerth at dealii dot org
@ 2003-12-26 23:36 ` pinskia at gcc dot gnu dot org
2004-08-16 18:37 ` bangerth at dealii dot org
4 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2003-12-26 23:36 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2003-12-26 23:17 -------
It might be that the C++ standard does not require a diagnostic of the problem.
--
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |accepts-invalid
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12222
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/12222] explicit initialization of static template members seems ignored
2003-09-09 10:16 [Bug c++/12222] New: explicit initialization of static template members seems ignored stefaandr at hotmail dot com
` (3 preceding siblings ...)
2003-12-26 23:36 ` pinskia at gcc dot gnu dot org
@ 2004-08-16 18:37 ` bangerth at dealii dot org
4 siblings, 0 replies; 7+ messages in thread
From: bangerth at dealii dot org @ 2004-08-16 18:37 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From bangerth at dealii dot org 2004-08-16 18:37 -------
gcc's behavior actually makes a lot more sense than anyone seems to
have noticed: with this code
----------------
template <typename T>
struct a { static int b1; };
template struct a<float>;
template <> int a<float>::b1;
int x = a<float>::b1;
-----------------
we indeed get no warning that a specialization is declared after
instantiating the template. However, that's about ok: we haven't
provided a definition of the static member, so it isn't instantiated
and the declaration of the specialization doesn't come too late.
On the other hand, for this code (not the presence of the definition)
------------------
template <typename T>
struct a { static int b1; };
template <typename T> int a<T>::b1;
template struct a<float>;
template <> int a<float>::b1;
int x = a<float>::b1;
------------------
we _do_ get an error:
g/x> /home/bangerth/bin/gcc-3.5-pre/bin/c++ -Wall -c x.cc
x.cc:6: error: redefinition of `int a<float>::b1'
x.cc:3: error: `int a<float>::b1' previously declared here
I think gcc is correct here. So closing.
W.
--
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |INVALID
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12222
^ permalink raw reply [flat|nested] 7+ messages in thread
[parent not found: <bug-12222-4@http.gcc.gnu.org/bugzilla/>]
end of thread, other threads:[~2012-02-01 3:07 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2003-09-09 10:16 [Bug c++/12222] New: explicit initialization of static template members seems ignored stefaandr at hotmail dot com
2003-09-09 14:08 ` [Bug c++/12222] " bangerth at dealii dot org
2003-09-09 17:53 ` stefaandr at hotmail dot com
2003-09-09 18:57 ` bangerth at dealii dot org
2003-12-26 23:36 ` pinskia at gcc dot gnu dot org
2004-08-16 18:37 ` bangerth at dealii dot org
[not found] <bug-12222-4@http.gcc.gnu.org/bugzilla/>
2012-02-01 3:07 ` pinskia at gcc dot gnu.org
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