Re: Temporary Objects as reference argument in functions

[Saravanan T S <saravanan at k dot st>]

>> Sun
>> Workshop and Dev Studio have no problems with it,
>> why not gcc?

Tried enabling "/Za" option in devstudio (ANSI Strict compilation) and it did give an error 
(compiled without the const qualifier as suggested by Long):

"test1\test1.cpp(19) : error C2665: 'test' : none of the 2 overloads can convert parameter 1 from type 'class MyClass'"

With Level 4 compilation without /Za in devstudio, warning:
"d:\vctests\test1\test1.cpp(19) : warning C4239: nonstandard extension used : 'argument' : conversion from 'class MyClass' to 'class MyClass &'"

So why gcc shouldn't...

#Sar

--- Long Li <long21st@yahoo.com> wrote:
>In C++, temporary objects are treated as const, so one
>way to solve the problem is to change 
>
>void test(MyClass & rTest)
>{
>}
>
>to
>
>void test(const MyClass &rTest)
>{
>}
>
>
>Best,
>
>
>
>Long
>
>--- Dirk Volkmar <Dirk.Volkmar@deutsche-boerse.com>
>wrote:
>> Hi!
>> 
>> We are porting some software to linux, that runs
>> under solaris and windows.  On
>> these plattforms we use the native compilers
>> (workshop/devstudio).
>> We have a problem with temporary objects that are
>> passes to functions with
>> reference parameters. I stripped the code down to an
>> example that looks like the
>> following code:
>> 
>> class MyClass
>> {
>>      public:
>>           MyClass(long lLong) : m_lLong(lLong) {};
>>      protected:
>>           long m_lLong;
>> };
>> 
>> void test(MyClass & rTest)
>> {
>> }
>> void test(const char * szTest)
>> {
>> }
>> int main()
>> {
>>      test(MyClass(1));
>>      return 0;
>> }
>> 
>> The compiler gives the following output:
>> g++ -c main.cpp
>> main.cpp: In function `int main()':
>> main.cpp:17: error: no matching function for call to
>> `test(MyClass)'
>> main.cpp:10: error: candidates are: void
>> test(MyClass&)
>> main.cpp:13: error:                 void test(const
>> char*)
>> 
>> If I delete the second test function I get the
>> following
>> g++ -c main.cpp
>> main.cpp: In function `int main()':
>> main.cpp:17: error: could not convert `MyClass(1)'
>> to `MyClass&'
>> main.cpp:10: error: in passing argument 1 of `void
>> test(MyClass&)'
>> 
>> If I declare a local object  instead using a
>> temporary object, it works:
>> int main()
>> {
>>      MyClass aObject(1);
>>      test(aObject);
>>      return 0;
>> }
>> 
>> Looking into the ansi standard I couldn't find that
>> the code is illeagal. Sun
>> Workshop and Dev Studio have no problems with it,
>> why not gcc?
>> O.K. I can use the upper workaround, but it is
>> anoying to change hundreds of
>> lines and don't know  why.
>> If someone has an explanation for this I would be
>> very happy.
>> 
>> Bye Dirk
>> 
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>> 
>
>
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