[Bug c++/53619] New: [c++11, regression] wrong capture of "this" in lambda in case of polymorphism

[Bug c++/53619] New: [c++11, regression] wrong capture of "this" in lambda in case of polymorphism

[vincenzo.innocente at cern dot ch]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53619

             Bug #: 53619
           Summary: [c++11, regression] wrong capture of "this" in lambda
                    in case of polymorphism
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: vincenzo.innocente@cern.ch


in this example "x" is wrongly captured
./a.out 
in foo 1
in lambda 4203472
Segmentation fault (core dumped)

removing the inheritance from B works "as expected"

It starts at the same time I had to capture "this" explicitly…
(sorry, only now had the time to debug it fully and reduce it some how)

#include<iostream>
struct CA {
  const int x;
  constexpr CA(int i) : x(i){}
};
struct B {
  virtual ~B(){}
};

struct A : public B, private CA {
  A(CA const c) : CA(c){}
  int foo(int *, int);
};


int A::foo(int * h, int l) {
  std::cout << "in foo " << x << std::endl;
  int a=0;
  auto k = [&a, &h ,this](int i) {
    std::cout << "in lambda " << x << std::endl;
    a+=h[x+i];
  };
  for (int i=0; i!=l; ++i)
     k(i);
  return a;
}



int main(int l, char **) {
  CA ca(1);
  A a(ca);
  int h[l+2]; h[0]=l;
  std::cout << a.foo(h,l) << std::endl;
}

[Bug c++/53619] [c++11, regression] wrong capture of "this" in lambda in case of polymorphism

[vincenzo.innocente at cern dot ch]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53619

--- Comment #1 from vincenzo Innocente <vincenzo.innocente at cern dot ch> 2012-06-09 16:16:32 UTC ---
reduced a bit showing how the offset is wrongly computed

struct CA {
  int x;
};
struct B {
  virtual ~B(){}
};

struct A : public B , CA  {
  int foo(int);
};


int A::foo(int l) {
  std::cout << "in foo " << x << " " << (void *)(&x) << std::endl;
  auto k = [this](int i) {
    std::cout << "in lambda " << x << " " << (void *)(&x) << std::endl;
    return x+i;
  };
  return k(l); 
}



int main(int l, char **) {
  A a; a.x=1;
  std::cout << a.foo(l) << std::endl;
}

 c++ -O2 -std=gnu++11 lambda_this2.cpp
 ./a.out 
in foo 1 0x7fff6c4de178
in lambda 4198320 0x7fff6c4de170
4198321

[Bug c++/53619] [c++11, regression] wrong capture of "this" in lambda in case of multiple inheritance

[vincenzo.innocente at cern dot ch]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53619

--- Comment #2 from vincenzo Innocente <vincenzo.innocente at cern dot ch> 2012-06-09 17:04:10 UTC ---
an even simpler test

 cat lambda_this2.cpp 
#include<cassert>
struct C {
  int x;
};
struct B {
  int q;
};
struct A : public B , C  {
  void foo();
};

void A::foo() {
  auto k = [this]() {return (void *)(&x);};
  assert(k()==(void *)(&x)); 
}

int main(int l, char **) {
  A a; a.foo();
}

c++ -std=gnu++11 lambda_this2.cpp; ./a.out
a.out: lambda_this2.cpp:14: void A::foo(): Assertion `k()==(void *)(&x)'
failed.
Aborted (core dumped)

[Bug c++/53619] [c++11, regression] wrong capture of "this" in lambda in case of multiple inheritance

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53619

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-06-09
                 CC|                            |jason at gcc dot gnu.org
     Ever Confirmed|0                           |1

--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> 2012-06-09 22:36:39 UTC ---
It is caused by revision 185768:

http://gcc.gnu.org/ml/gcc-cvs/2012-03/msg01099.html

[Bug c++/53619] [4.8 regression] [C++11] wrong capture of "this" in lambda in case of multiple inheritance

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53619

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++/53619] [4.8 regression] [C++11] wrong capture of "this" in lambda in case of multiple inheritance

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53619

--- Comment #4 from Jason Merrill <jason at gcc dot gnu.org> 2012-07-03 05:03:45 UTC ---
Author: jason
Date: Tue Jul  3 05:03:34 2012
New Revision: 189191

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=189191
Log:
    PR c++/53619
    * pt.c (in_template_function): New.
    * cp-tree.h: Declare it.
    * class.c (build_base_path, resolves_to_fixed_type_p): Use it.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-this5.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/class.c
    trunk/gcc/cp/cp-tree.h
    trunk/gcc/cp/pt.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/53619] [4.8 regression] [C++11] wrong capture of "this" in lambda in case of multiple inheritance

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53619

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.8.0

--- Comment #5 from Jason Merrill <jason at gcc dot gnu.org> 2012-07-03 05:06:17 UTC ---
Fixed.