http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57958
Bug ID: 57958
Summary: Incorrect code generation in lambda with argument of
type reference to template class
Product: gcc
Version: 4.7.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: tudorb at fb dot com
Created attachment 30538
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30538&action=edit
Source file that exhibits broken behavior
gcc (tested in 4.6.2 and 4.7.1) generates incorrect code for the "fn" lambda,
resulting in an extraneous destructor call. Compiler with -O0 (this is reduced
from a more complex example involving shared_ptr which exhibited the bug with
-O3 as well).
Source attached. The bug remains without #include <cstdio> and without the
call to printf, which are there just for exposition.
x86_64 disassembly (from gcc 4.7.1):
Dump of assembler code for function operator()(Foo<Data> const&) const:
0x00000000004006ec <+0>: push %rbp
0x00000000004006ed <+1>: mov %rsp,%rbp
0x00000000004006f0 <+4>: sub $0x30,%rsp
0x00000000004006f4 <+8>: mov %rdi,-0x18(%rbp)
0x00000000004006f8 <+12>: mov %rsi,-0x20(%rbp)
0x00000000004006fc <+16>: mov %rdx,-0x28(%rbp)
=> 0x0000000000400700 <+20>: mov -0x28(%rbp),%rdx
0x0000000000400704 <+24>: lea -0x1(%rbp),%rax
0x0000000000400708 <+28>: mov %rdx,%rsi
0x000000000040070b <+31>: mov %rax,%rdi
0x000000000040070e <+34>: callq 0x400794 <Foo<Data>::Foo(Foo<Data>
const&)>
0x0000000000400713 <+39>: lea -0x1(%rbp),%rax
0x0000000000400717 <+43>: mov %rax,%rdi
0x000000000040071a <+46>: callq 0x4007b2 <Foo<Data>::~Foo()>
0x000000000040071f <+51>: leaveq
0x0000000000400720 <+52>: retq
End of assembler dump.
The bug only happens if Foo is a template. If Foo is not a template, the code
is correct:
Dump of assembler code for function operator()(Foo const&) const:
0x00000000004006ec <+0>: push %rbp
0x00000000004006ed <+1>: mov %rsp,%rbp
0x00000000004006f0 <+4>: sub $0x20,%rsp
0x00000000004006f4 <+8>: mov %rdi,-0x8(%rbp)
0x00000000004006f8 <+12>: mov %rsi,-0x10(%rbp)
0x00000000004006fc <+16>: mov %rdx,-0x18(%rbp)
=> 0x0000000000400700 <+20>: mov -0x18(%rbp),%rdx
0x0000000000400704 <+24>: mov -0x8(%rbp),%rax
0x0000000000400708 <+28>: mov %rdx,%rsi
0x000000000040070b <+31>: mov %rax,%rdi
0x000000000040070e <+34>: callq 0x4007a6 <Foo::Foo(Foo const&)>
0x0000000000400713 <+39>: mov -0x8(%rbp),%rax
0x0000000000400717 <+43>: leaveq
0x0000000000400718 <+44>: retq
End of assembler dump.
