http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53157
Bug #: 53157
Summary: within lambda, error: lvalue required as unary ‘&’
operand
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: [email protected]
ReportedBy: [email protected]
the following code failed to compile with g++-4.7.0
------------------- BEGIN -------------------
void f(const int*) { }
void g() {
const int N = 10;
[=] {
int arr[N]; // OK: not an odr-use, refers to automatic variable
f(&N); // OK: causes N to be captured; &N points to the
// corresponding member of the closure type
}
}
int main ()
{
return 0;
}
------------------- BEGIN -------------------
the f and g are copied from c++11 5.1.2/17.
compiled with :
~/gcc/4.7.0/bin/c++ --std=c++11 -Wall t1.cc
g++-4.7.0 gives me two errors :
(1) for the call to f(&N); : error: lvalue required as unary ‘&’ operand
(2) at the end of the lambda : error: expected ‘;’ before ‘}’ token
the standard says that the use of f(&N) is valid because the N is odr-used and
should be implicitly captured by value, so &N returns a pointer to the data
member of the closure type that is a copy of the original N.
my g++ -v is :
Reading specs from
/home/meng/gcc/4.7.0/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/specs
COLLECT_GCC=/home/meng/gcc/4.7.0/bin/c++
COLLECT_LTO_WRAPPER=/home/meng/gcc/4.7.0/libexec/gcc/x86_64-unknown-linux-gnu/4.7.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ./configure --prefix=/home/meng/gcc/4.7.0
--enable-languages=c,c++ -disable-multilib
Thread model: posix
gcc version 4.7.0 (GCC)
my uname -a is :
Linux meng-laptop 2.6.32-38-generic #83-Ubuntu SMP Wed Jan 4 11:12:07 UTC 2012
x86_64 GNU/Linux
