string redeclaration in function, why is required?

Code:

int main(int argc, char* argv[]){
	argc--;
	if ( argc < 1){
		cout << "Usage:" << endl << "h5inspect file.h5" << endl;
		return 0;
	}
	//iterate *.h5 in ascending order
	for (int count = 1; count <= argc; count ++){ 
		
		char iterchar; 
		string filename = argv[count]; 
		cout << "HDF5 \"" << filename << "\" { "<< endl;
		dataset_loader dset(string(filename));

The last line of code is of interest. The string filename is already declared as a string, but the function only works when the parameter is given as "string(filename)" or "string& filename". But filename is already defined as a string; why does it still required the string 'filename' to be made a string, again?!

Originally Posted by elninio

Code:

int main(int argc, char* argv[]){
	argc--;
	if ( argc < 1){
		cout << "Usage:" << endl << "h5inspect file.h5" << endl;
		return 0;
	}
	//iterate *.h5 in ascending order
	for (int count = 1; count <= argc; count ++){ 
		
		char iterchar; 
		string filename = argv[count]; 
		cout << "HDF5 \"" << filename << "\" { "<< endl;
		dataset_loader dset(string(filename));

The last line of code is of interest. The string filename is already declared as a string, but the function only works when the parameter is given as "string(filename)" or "string& filename". But filename is already defined as a string; why does it still required the string 'filename' to be made a string, again?!

I doubt it does. Do you get an error if you remove it?

--
Mats

of course I do!

Code:

/tmp/cc6ghKxc.o: In function `main':
h5inspect.cpp:(.text+0x125): undefined reference to `H5check_version'
h5inspect.cpp:(.text+0x12c): undefined reference to `H5::FileAccPropList::DEFAULT'
h5inspect.cpp:(.text+0x131): undefined reference to `H5::FileCreatPropList::DEFAULT'
h5inspect.cpp:(.text+0x13d): undefined reference to `H5::H5File::H5File(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned int, H5::FileCreatPropList const&, H5::FileAccPropList const&)'
h5inspect.cpp:(.text+0x1f1): undefined reference to `H5::H5File::close()'
h5inspect.cpp:(.text+0x201): undefined reference to `H5::H5File::close()'
h5inspect.cpp:(.text+0x237): undefined reference to `H5::H5File::~H5File()'
h5inspect.cpp:(.text+0x247): undefined reference to `H5::H5File::~H5File()'
h5inspect.cpp:(.text+0x283): undefined reference to `H5::H5File::~H5File()'
h5inspect.cpp:(.text+0x291): undefined reference to `H5::H5File::~H5File()'
collect2: ld returned 1 exit status

What are the constructors of dataset_loader? Is dataset_loader a typedef for a template?

I can imagine something like this happening if the string constructor call causes a different template constructor be called. Using a string constructor like that actually evaluates to a const string. If there are a different template constructors for const and non const strings, then there will be a difference in which constructor is called. But to make undefined references to appear just by calling the constructor requires that the constructor or it's class be a template.

But that would be a very obscure occurrence.

dataset_loader is neither a namespace or a template

You are hiding information about your code. Provide a small but complete example that exhibits the behaviours of interest.

My bet is that dset is a macro. I wouldn't be surprised if dataset_loader and string are also macros with different meanings from what people would normally assume by looking at your code.

The only other explanation for getting linker errors is that you are linking against different libraries or objects when you change the code.

Either way, you are providing information that is incomplete, but just enough to deceive.

Got it, added debug flag to g++. Turns out I was missing libs, the includes were there but the lib directory was wrong. Sorry if I wasn't providing enough information, I would have to send you the files to tell more! I did not write these files, I have received them from a colleague, so I do not know much about them.