Given:
MY_CLASS* ptr = MY_CLASS::GetSomeInstance();
What is the correct way to output ptr to std::cerr, so I can log its value? Note I don't want to write the class, just the address.
views:
56answers:
3
+7
A:
operator<< is overloaded to take a const void*, so you can simply insert the pointer into the stream:
std::cerr << ptr;
The exception is that if the pointer is a const char*, it will be interpreted as a pointer to a C string. To print the pointer, you need to cast it explicitly to a const void*:
std::cerr << static_cast<const void*>(ptr);
James McNellis
2010-07-14 22:53:19
Except for the stupid `::std::endl` this is an excellent answer. You should use `'\n'` instead, especially for `::std::cerr`.
Omnifarious
2010-07-14 23:20:01
@Omnifarious: I just removed it altogether since it's not important to the answer anyway.
James McNellis
2010-07-14 23:21:23
@Omnifarious, what's the beef with endl? Is it the flush?
David Gladfelter
2010-07-14 23:24:20
@David - That, and the fact that it's used so often people get the bizarre idea that `'\n'` isn't platform independent and `::std::endl` __has__ to be used. 95% of the time I see `::std::endl` used the flush is totally unnecessary. Flushing is very expensive, and in the case of `::std::cerr` completely superfluous.
Omnifarious
2010-07-14 23:28:42
+1
A:
You can leverage boost format for printf like formatting:
std::cerr << format("%p", ptr) << endl;
%p formats pointer - should be portable between x86 and x64.
Igor Zevaka
2010-07-14 22:56:22
+1
A:
While using operator<< works, you could also use <cstdio>:
#include <cstdio>
...
MY_CLASS* ptr = MY_CLASS::GetSomeInstance();
fprintf(std::stderr, "Pointer address: %p", ptr);
tjko
2010-07-14 22:57:39