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problem with fprintf [message #29217]

Mon, 11 October 2010 14:08

o_wild
Messages: 28
Registered: December 2008
Location: Urmqi

Promising Member

The following code is excerpt of an opensource software, but there is error when compiled.

fprintf(ofp,"%s\n",mes1); // mes1 is of type String

The error message is
cannot pass objects of non-trivially-copyable type 'class Upp::String' through '...'

The software can be compiled with both mingw and MSVC as the developer says. Since I have problem using MSVC due to C2001 error(new line in constant), I choose MingGW 4.5.0.

Is their any substitute for 'fprintf'? by the way, i tested 'printf' and found the same problem.

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Re: problem with fprintf [message #29218 is a reply to message #29217]

Mon, 11 October 2010 14:26

cbpporter
Messages: 1427
Registered: September 2007

Ultimate Contributor

The problem is that when trying to pass your string as an argument ta a variable argument function the compiler has no means of knowing that you are trying to pass a C string. In such cases you must explicitly specify that you want to convert from String to C string. Try ~mes1, mes1.Begin() or casting to (char*).

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Re: problem with fprintf [message #29256 is a reply to message #29218]

Wed, 13 October 2010 12:54

o_wild
Messages: 28
Registered: December 2008
Location: Urmqi

Promising Member

Thanks. Both will do.

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Re: problem with fprintf [message #29332 is a reply to message #29217]

Fri, 15 October 2010 14:44

mirek
Messages: 14265
Registered: November 2005

Ultimate Member

o_wild wrote on Mon, 11 October 2010 08:08

The following code is excerpt of an opensource software, but there is error when compiled.

fprintf(ofp,"%s\n",mes1); // mes1 is of type String

Is their any substitute for 'fprintf'? by the way, i tested 'printf' and found the same problem.

Yes, Format. It is typesafe - you would not encounter above kind of problem there.

So in "true" U++ the code would look like this:

FileOut ofp;
....
ofp.Put(Format("%d\n", mes1);

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