On Nov 15, 2006, at 9:30 AM, Ian Lance Taylor wrote:
Wai-chung Poon <tsdmilan@xxxxxxxxxxxx> writes:I encountered compilation problems with the following code: << A.h >> #include <vector> namespace Ser { template <class T> size_t StreamSize(const std::vector<T> &v) { size_t Result = 0; for (int i = 0; i < v.size(); ++i) Result += StreamSize(v[i]); return Result; } } << B.h >> #include "cx.h" // defines CCX namespace Ser { size_t StreamSize(const CCX *p); // definition in B.cpp } << C.cpp >> #include "A.h" // Line (1) #include "B.h" // Line (2) using namespace Ser; using namespace std; int main(int argc, char *argv[]) { vector<CCX *> v; size_t Size = StreamSize(v); } ------ The returned error is "No matching function for call to StreamSize(CCX *const&). If I swap line (1) with line (2) in C.cpp, or remove the namespace definition in B.cpp, the code compiles without any problem. Besides, the above code used to work fine with gcc 2.96 but no longer works once I upgraded the gcc to 4.1.1. If I don't swap the two lines in C.cpp, is there any other way to resolve this? Thanks.Names which are not dependent on template parameters, such as, in this case, StreamSize, are looked up at template definition time, not at template instantiation time. This is known as two-phase lookup.
Sorry to be such a pest about this. I still don't understand this two phase lookup. Here is my logic:
StreamSize(v[i]) depends upon v[i] which depends upon std::vector<V> which depends upon V. So, StreamSize does (according to my logic) depend upon the template argument. Where did I go wrong?
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