[Bug c++/51494] Legal program rejection - capturing "this" when using static method inside lambda
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51494
Arthur O'Dwyer changed:
What|Removed |Added
CC||arthur.j.odwyer at gmail dot
com
--- Comment #11 from Arthur O'Dwyer ---
Is there a workaround available for GCC 4.6.3?
That is, I have some code that looks like
class A {
static A *unwrap(void *p);
static void api_helper(void *p) { A *a = unwrap(p); ... }
void init() { register_with_api(_helper); }
};
where "api_helper" exists only to conform to the requirements of the external
API.
To reduce the surface area of the class, I'd like to refactor this into
something like
class A {
static A *unwrap(void *p);
void init() {
auto api_helper = [](void *a) { A *a = unwrap(p); ... };
register_with_api(api_helper);
}
};
but at the moment I'm hitting this bug in gcc (Ubuntu/Linaro 4.6.3-1ubuntu5)
4.6.3 because "api_helper" happens to also want to use some static members of
A.
I understand if there's no workaround (beyond "upgrade to gcc 4.8"), but if
there IS one, I'd like to know it!
[Bug c++/51494] Legal program rejection - capturing this when using static method inside lambda
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51494 --- Comment #9 from Jason Merrill jason at gcc dot gnu.org 2013-03-08 16:03:57 UTC --- Author: jason Date: Fri Mar 8 16:03:48 2013 New Revision: 196549 URL: http://gcc.gnu.org/viewcvs?root=gccview=revrev=196549 Log: PR c++/51494 PR c++/51884 PR c++/56222 * tree.c (maybe_dummy_object): Don't capture 'this'. * semantics.c (maybe_resolve_dummy): New. (finish_non_static_data_member): Use it. (finish_qualified_id_expr): Don't test is_dummy_object. * cp-tree.h: Declare maybe_resolve_dummy. * call.c (build_new_method_call_1): Use it. Added: trunk/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-this11.C Modified: trunk/gcc/cp/ChangeLog trunk/gcc/cp/call.c trunk/gcc/cp/cp-tree.h trunk/gcc/cp/semantics.c trunk/gcc/cp/tree.c
[Bug c++/51494] Legal program rejection - capturing this when using static method inside lambda
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51494 Jason Merrill jason at gcc dot gnu.org changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution||FIXED Target Milestone|--- |4.8.0 --- Comment #10 from Jason Merrill jason at gcc dot gnu.org 2013-03-08 16:10:48 UTC --- Fixed for 4.8.
[Bug c++/51494] Legal program rejection - capturing this when using static method inside lambda
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51494 Jason Merrill jason at gcc dot gnu.org changed: What|Removed |Added Status|NEW |ASSIGNED AssignedTo|unassigned at gcc dot |jason at gcc dot gnu.org |gnu.org |
[Bug c++/51494] Legal program rejection - capturing this when using static method inside lambda
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51494 Jason Merrill jason at gcc dot gnu.org changed: What|Removed |Added CC||vladimir.bayda at gmail dot ||com --- Comment #8 from Jason Merrill jason at gcc dot gnu.org 2013-03-04 18:15:08 UTC --- *** Bug 55828 has been marked as a duplicate of this bug. ***
[Bug c++/51494] Legal program rejection - capturing this when using static method inside lambda
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51494
kpx1894 kpx1894 at gmail dot com changed:
What|Removed |Added
CC||kpx1894 at gmail dot com
--- Comment #7 from kpx1894 kpx1894 at gmail dot com 2012-12-07 15:18:03 UTC
---
This bug is still present in GCC 4.7.2. There are cases where capturing this
(as a workaround) is not possible:
--
#include iostream
struct Test
{
void (*get())()
{
return [](){ Test::sf(); };
}
static void sf()
{
std::cout Test::sf std::endl;
}
};
int main()
{
Test test;
auto f = test.get();
(*f)();
}
--
[Bug c++/51494] Legal program rejection - capturing this when using static method inside lambda
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51494 Paolo Carlini paolo.carlini at oracle dot com changed: What|Removed |Added Status|ASSIGNED|NEW AssignedTo|paolo.carlini at oracle dot |unassigned at gcc dot |com |gnu.org --- Comment #6 from Paolo Carlini paolo.carlini at oracle dot com 2012-08-16 09:53:36 UTC --- Not actively working on this.
[Bug c++/51494] Legal program rejection - capturing this when using static method inside lambda
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51494
gcc-bugx at mailinator dot com changed:
What|Removed |Added
CC||gcc-bugx at mailinator dot
||com
--- Comment #4 from gcc-bugx at mailinator dot com 2012-06-04 08:21:54 UTC ---
Probably related error: this capture ignored on explicit instantiation.
8---
struct A
{
static void f() {}
template typename T
void foo()
{
[this] () { f(); };
}
};
template void A::fooint();
8---
Compiler version output:
$ g++ -std=c++11 -c -v y.cc
Using built-in specs.
COLLECT_GCC=g++
Target: x86_64-unknown-linux-gnu
Configured with: ./configure --enable-languages=c,c++ --prefix=/home/x
Thread model: posix
gcc version 4.7.0 (GCC)
COLLECT_GCC_OPTIONS='-std=c++11' '-c' '-v' '-shared-libgcc' '-mtune=generic'
'-march=x86-64'
/home/x/libexec/gcc/x86_64-unknown-linux-gnu/4.7.0/cc1plus -quiet -v
-D_GNU_SOURCE y.cc -quiet -dumpbase y.cc -mtune=generic -march=x86-64 -auxbase
y -std=c++11 -version -o /tmp/ccdFvfri.s
GNU C++ (GCC) version 4.7.0 (x86_64-unknown-linux-gnu)
compiled by GNU C version 4.7.0, GMP version 4.3.2, MPFR version
3.0.0-p8, MPC version 0.9
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
ignoring nonexistent directory
/home/x/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../x86_64-unknown-linux-gnu/include
#include ... search starts here:
#include ... search starts here:
/home/x/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../include/c++/4.7.0
/home/x/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../include/c++/4.7.0/x86_64-unknown-linux-gnu
/home/x/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../include/c++/4.7.0/backward
/home/x/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/include
/usr/local/include
/home/x/include
/home/x/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/include-fixed
/usr/include
End of search list.
GNU C++ (GCC) version 4.7.0 (x86_64-unknown-linux-gnu)
compiled by GNU C version 4.7.0, GMP version 4.3.2, MPFR version
3.0.0-p8, MPC version 0.9
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: ...
y.cc: In instantiation of ‘A::foo() [with T = int]::lambda()’:
y.cc:8:4: required from ‘struct A::foo() [with T = int]::lambda()’
y.cc:8:3: required from ‘void A::foo() [with T = int]’
y.cc:11:27: required from here
y.cc:8:17: error: ‘this’ was not captured for this lambda function
[Bug c++/51494] Legal program rejection - capturing this when using static method inside lambda
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51494 --- Comment #5 from Jason Merrill jason at gcc dot gnu.org 2012-06-04 19:35:40 UTC --- The testcases in comments 2 and 4 are PR 53137, which is fixed for 4.7.1.
[Bug c++/51494] Legal program rejection - capturing this when using static method inside lambda
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51494
Andy Lutomirski luto at mit dot edu changed:
What|Removed |Added
CC||luto at mit dot edu
--- Comment #2 from Andy Lutomirski luto at mit dot edu 2012-05-03 21:53:18
UTC ---
This seems to have gotten worse in gcc 4.7. This code is now rejected as well:
This code:
struct A
{
static void func1() {}
};
templatetypename T
struct B : public A
{
void func2() const
{
func3([]{ func1(); });
}
templatetypename Func
void func3(Func f) const
{
}
};
template class Bint;
The error is:
template_bug.cc: In instantiation of ‘BT::func2() const [with T =
int]::lambda()’:
template_bug.cc:11:22: required from ‘struct BT::func2() const [with T =
int]::lambda()’
template_bug.cc:11:5: required from ‘void BT::func2() const [with T = int]’
template_bug.cc:20:16: required from here
template_bug.cc:11:16: error: redeclaration of ‘const Bint* const
BT::func2() const [with T = int]::lambda()::__this’
template_bug.cc:11:22: note: previous declaration ‘const Bint* const
BT::func2() const [with T = int]::lambda()::__this’
template_bug.cc:11:16: error: redeclaration of ‘const Bint* const this’
template_bug.cc:11:22: error: ‘const Bint* const this’ previously declared
here
template_bug.cc:15:8: error: ‘void BT::func3(Func) const [with Func =
BT::func2() const [with T = int]::lambda(); T = int]’, declared using local
type ‘BT::func2() const [with T = int]::lambda()’, is used but never
defined [-fpermissive]
Your patch fixes this test case, too.
[Bug c++/51494] Legal program rejection - capturing this when using static method inside lambda
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51494 --- Comment #3 from Paolo Carlini paolo.carlini at oracle dot com 2012-05-03 23:04:35 UTC --- A slightly improved patch is available here: http://gcc.gnu.org/ml/gcc-patches/2012-02/msg00429.html but see the comments. I'm not sure I will be able soon enough to address the non-trivial comments and post a new version.
[Bug c++/51494] Legal program rejection - capturing this when using static method inside lambda
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51494 Paolo Carlini paolo.carlini at oracle dot com changed: What|Removed |Added Status|UNCONFIRMED |ASSIGNED Last reconfirmed||2011-12-22 CC|ulidtko at gmail dot com| AssignedTo|unassigned at gcc dot |paolo.carlini at oracle dot |gnu.org |com Ever Confirmed|0 |1 --- Comment #1 from Paolo Carlini paolo.carlini at oracle dot com 2011-12-22 01:38:46 UTC --- On it.
