http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54905
Bug #: 54905
Summary: invalid use of qualified-name 'std::cout'
Classification: Unclassified
Product: gcc
Version: 4.6.4
Status: UNCONFIRMED
Severity: blocker
Priority: P3
Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: ace.of.zeros...@gmail.com
The code below builds fine with any version of GCC 4.x
########
#include <iostream>
void Test(std::ostream &stream) {
stream << "Hello, World!" << std::endl;
}
int main() {
Test(std::cout);
return 0;
}
########
But
GCC 4.2.1, 4.4.0, 4.6.4 and 4.7.3 refuse to build the below code while VC++10,
VC++11 and both CLANG 3.0 and 3.1 are building it without any issue or warning.
[ I got it from here:
http://stackoverflow.com/questions/8629382/debug-macro-for-c-with-variable-arguments-without-the-format-string
]
########
#include <iostream>
#include <string>
class VariadicToOutputStream
{
public:
VariadicToOutputStream(std::ostream& s, const std::string& separator = " ")
: m_stream(s), m_hasEntries(false), m_separator(separator) {}
template<typename ObjectType>
VariadicToOutputStream& operator , (const ObjectType& v)
{
if (m_hasEntries) m_stream << m_separator;
m_stream << v;
m_hasEntries=true;
return *this;
}
~VariadicToOutputStream()
{
m_stream << std::endl;
}
private:
std::ostream& m_stream;
bool m_hasEntries;
std::string m_separator;
};
#define VARIADIC_TO_STDOUT(...) \
VariadicToOutputStream(std::cout),__VA_ARGS__;
int main() {
VARIADIC_TO_STDOUT(1, 0.5f, "a string");
return 0;
}
########
The error produced by GCC:
########
main.cpp: In function 'int main()':
main.cpp:31:2: error: invalid use of qualified-name 'std::cout'
main.cpp:31:2: error: expected unqualified-id before numeric constant
########
Versions of GCC that I've used:
g++ (GCC) 4.2.1 20070831 patched [FreeBSD]
g++46 (FreeBSD Ports Collection) 4.6.4 20120928 (prerelease)
g++47 (FreeBSD Ports Collection) 4.7.3 20120929 (prerelease)
MinGW g++ (GCC) 4.4.0
