Get the 'L' out of here!

  • Thread starter Thread starter Peter Oliphant
  • Start date Start date
P

Peter Oliphant

The following line of code:

m_Font = gcnew System::Drawing::Font( L"Arial", 10 ) ;

also works like this:

m_Font = gcnew System::Drawing::Font( "Arial", 10 ) ;

Note that the 'L' in front of "Arial" is missing in the second version. What
is the difference, if any, between L"string" and "string"?

[==P==]
 
Hi Peter,
The following line of code:

m_Font = gcnew System::Drawing::Font( L"Arial", 10 ) ;

also works like this:

m_Font = gcnew System::Drawing::Font( "Arial", 10 ) ;

Note that the 'L' in front of "Arial" is missing in the second version.
What is the difference, if any, between L"string" and "string"?
Click to expand...

Well, the "L" represents a unicode string to the compiler, so it saves a bit
of work. However, neither is optimal in this case. From what I seem to
remember, both will invoke a System::String conversion that converts from an
unmanaged char/wchar_t pointer to a System::String instance (possibly
invoking an encoding conversion), which is totally unnecessary.

Managed C++ actually includes a syntax to ensure you define a literal that
is already a System::String instance and that is subject to all the
interning the runtime uses for this, via de 'S' prefix. So the correct way
really is:

m_Font = gcnew System::Drawing::Font( S"Arial", 10 ) ;

That said, this is unnecessary in C++/CLI, because the compiler can
distinguish the kind of literal from context, I believe, and use a managed
string literal when necessary.
 
Hi Tomas!
Managed C++ actually includes a syntax to ensure you define a literal that
is already a System::String instance and that is subject to all the
interning the runtime uses for this, via de 'S' prefix. So the correct way
really is:
Click to expand...

Yes. This cas the case in VC7(.1) (managed C++) but in C++/CLI MS
changed this behaviour and now completely ignores the prefix for string
literals in conjunction with System::String

See: Porting and Upgrading: String Literal
http://msdn2.microsoft.com/ms235263

The compiler just converts the string literal to an System::String,
regardless of the prefix.

See: System::String Handling in Visual C++
http://msdn2.microsoft.com/ms177218

--
Greetings
Jochen

My blog about Win32 and .NET
http://blog.kalmbachnet.de/
 
Hi Jochen,
Yes. This cas the case in VC7(.1) (managed C++) but in C++/CLI MS changed
this behaviour and now completely ignores the prefix for string literals
in conjunction with System::String
Click to expand...

I think that was what I meant when I said "That said, this is unnecessary in
C++/CLI, because the compiler can
distinguish the kind of literal from context, I believe, and use a managed
string literal when necessary." :)

The reason I mentioned the 'S' was because I got confused thinking the user
was still doing MC++ development. too much language dyslexia :)

Thanks for pointing it out
 
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