[Bug c++/78986] [7/8/9 Regression] template inner classes are not affected by access specifiers
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78986
Balakrishnan B changed:
What|Removed |Added
CC||balakrishnan.erode at gmail
dot co
||m
--- Comment #2 from Balakrishnan B ---
This has nothing to do with inheritance. If the inner class is template, access
specifiers are ignored. Simpler example:
class A {
struct B1 {};
template
struct B2 {};
};
void foo() {
//A::B1 b1; //This doesn't compile (GOOD)
A::B2 b2; // This compiles (BAD)
}
Explorer: https://gcc.godbolt.org/z/S0YBPu
Bug is present in all versions between GCC 6.1 to trunk. GCC5 and earlier are
good.
[Bug c++/65143] [C++11] missing devirtualization for virtual base in "final" classes
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65143 Balakrishnan B changed: What|Removed |Added Version|4.9.2 |5.3.0 Known to fail||5.3.0 Severity|normal |major
[Bug c++/53792] [C++11] improving compiler-time constexpr evaluation
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53792
Balakrishnan B balakrishnan.erode at gmail dot com changed:
What|Removed |Added
CC||balakrishnan.erode at gmail
dot co
||m
--- Comment #8 from Balakrishnan B balakrishnan.erode at gmail dot com ---
Another testcase with c++14 extended constexpr (i.e supports loops and more
than one statement).
Code:
templateclass T
void sink(T);
constexpr unsigned foo(){
unsigned i = 1;
while((i1) i){
i = i1;
}
return i;
}
templateunsigned i
struct Foo
{
};
void bar(){
sink(foo());
sink(Foofoo(){});
}
Assembly for bar:
clang3.5.1 -O3 -std=c++14
bar():# @bar()
pushq %rax
movl$-2147483648, %edi # imm = 0x8000
callq void sinkunsigned int(unsigned int)
popq%rax
jmp void sinkFoo2147483648u (Foo2147483648u) # TAILCALL
gcc5.1.0 -O3 -std=c++14
bar():
movl$32, %eax
movl$1, %edi
jmp .L2
.L3:
movl%edx, %edi
.L2:
subl$1, %eax
leal(%rdi,%rdi), %edx
jne .L3
subq$8, %rsp
callvoid sinkunsigned int(unsigned int)
subq$8, %rsp
pushq $0
callvoid sinkFoo2147483648u (Foo2147483648u)
addq$24, %rsp
ret
Live demo: http://goo.gl/b56Q5k
[Bug c++/65143] [C++11] missing devirtualization for virtual base in final classes
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65143 --- Comment #4 from Balakrishnan B balakrishnan.erode at gmail dot com --- Thanks for confirming!
[Bug c++/65143] [C++11] missing devirtualization for virtual base in final classes
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65143 --- Comment #2 from Balakrishnan B balakrishnan.erode at gmail dot com --- Can someone please confirm the bug?
[Bug c++/65143] New: [C++11] missing devirtualization for virtual base in final classes
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65143
Bug ID: 65143
Summary: [C++11] missing devirtualization for virtual base in
final classes
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: balakrishnan.erode at gmail dot com
When a class is marked final, it can devirtualize access to all base classes as
its layout is known. This is missing in gcc.
struct A
{
int i();
};
struct B : public virtual A
{
int get()
{
return A::i() + 1;
}
};
struct C final : public B
{
int get()
{
return A::i() + 2;
}
};
int foo(C c)
{
return c.get(); // Need not go via vtable pointer as class C is final
}
int foo(B b2)
{
return b2.get(); // This has to go via vtable as most derived class can
change the location of A
}
Assembly: Both do virtual dispatch
foo(C):
subq$8, %rsp
movq(%rdi), %rax
addq-24(%rax), %rdi
callone::A::i()
addq$8, %rsp
addl$2, %eax
ret
foo(B):
subq$8, %rsp
movq(%rdi), %rax
addq-24(%rax), %rdi
callone::A::i()
addq$8, %rsp
addl$1, %eax
ret
Complete example:
gcc: http://goo.gl/U4KEvj
clang: http://goo.gl/PpQCkd -- Clang does this optimization
[Bug c++/65143] [C++11] missing devirtualization for virtual base in final classes
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65143 Balakrishnan B balakrishnan.erode at gmail dot com changed: What|Removed |Added CC||balakrishnan.erode at gmail dot co ||m See Also||https://gcc.gnu.org/bugzill ||a/show_bug.cgi?id=49488 --- Comment #1 from Balakrishnan B balakrishnan.erode at gmail dot com --- I mean access to A::i() can be devirtualized in C::get().
[Bug c++/55914] [C++11] Pack expansion fails in lambda expressions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55914 Balakrishnan B balakrishnan.erode at gmail dot com changed: What|Removed |Added CC||balakrishnan.erode at gmail dot co ||m --- Comment #8 from Balakrishnan B balakrishnan.erode at gmail dot com --- Is this bug fixed in 4.8.3? I don't find here Known to work:4.9.0 Known to fail:4.7.2, 4.8.0
[Bug libstdc++/53631] [C++11] regex is unimplemented
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53631 Balakrishnan B balakrishnan.erode at gmail dot com changed: What|Removed |Added CC||balakrishnan.erode at gmail ||dot com --- Comment #5 from Balakrishnan B balakrishnan.erode at gmail dot com 2013-03-28 15:17:16 UTC --- Why is the priority just normal? I think its very much needed. I wish there was a vote button for the issues.
[Bug c++/11750] class scope using-declaration lookup not implemented
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11750
Balakrishnan B balakrishnan.erode at gmail dot com changed:
What|Removed |Added
CC||balakrishnan.erode at gmail
||dot com
--- Comment #6 from Balakrishnan B balakrishnan.erode at gmail dot com
2011-01-12 16:57:07 UTC ---
(In reply to comment #0)
Paragraph 10.3/2 in the C++ standard [ISO/IEC 14882:1998] provides the
following
code example:
quote
struct A {
virtual void f();
};
struct B : virtual A {
virtual void f();
};
struct C : B , virtual A {
using A::f;
};
void foo() {
C c;
c.f(); // calls B::f, the final overrider
c.C::f(); // calls A::f because of the using-declaration
}
/quote
When a similar program is compiled using G++ 3.3, the method call 'c.f()' in
function foo() incorrectly invokes A::f and not B::f as specified in the
standard.
example
code main.cpp
#include iostream
struct A {
virtual void f() { std::cout A::f()\n; }
};
struct B : virtual A {
virtual void f() { std::cout B::f()\n; }
};
struct C : B, virtual A {
using A::f;
};
int main()
{
C c;
c.f(); // ERROR - Incorrectly invokes A::f
c.C::f(); // OK - Invokes A::f
}
/code
build
$ g++ main.cpp
$ ldd a.out
libstdc++.so.5 =
/usr/local/gcc/3.3/lib/gcc-lib/i686-pc-linux-gnu/3.3/libstdc++.so.5
(0x40017000)
libm.so.6 = /lib/tls/libm.so.6 (0x400e4000)
libgcc_s.so.1 =
/usr/local/gcc/3.3/lib/gcc-lib/i686-pc-linux-gnu/3.3/libgcc_s.so.1
(0x40106000)
libc.so.6 = /lib/tls/libc.so.6 (0x4200)
/lib/ld-linux.so.2 = /lib/ld-linux.so.2 (0x4000)
/build
output
$ ./a.out
A::f()
A::f()
/output
/example
Im using g++ 4.4.5
With the same example with my main function as below,
int main()
{
C c;
c.f() // Calls A::f
C* pc = c;
pc-f() // Calls B::f
}
With the same object when accessed directly produces different results and when
accessed using a pointer of same type produces a different result. Even if gcc
violates standard, there has to be some proper explanation.
