A mysterious undocumented keyword?

  • Thread starter Thread starter gil
  • Start date Start date
G

gil

Hi,

In VS 2005 (SP1), the following code does not compile:

=============
typedef int _sptr ;
_sptr p = 1;
=============

the compiler emits the following:

source1.cpp(1) : warning C4091: 'typedef ' : ignored on left of 'int'
when no variable is declared
source1.cpp(2) : error C4430: missing type specifier - int assumed.
Note: C++ does not support default-int

After pulling half my hair out, I found that changing _sptr to almost
anything else (e.g. _sptr1), makes the code compile. Note that:
1. _sptr is not mentioned anywhere in the MSDN database.
2. I suspect that this didn't happen to me before upgrading my VS2005
to SP1.
3. Removing the '_' made the word 'sptr' change to blue as if a
keyword, again, sptr isn't mentioned in MSDN. (this happened on one
PC, on another it didn't).

Can anyone please help, what is _sptr?

Thanks,
Gil Moses.
 
typedef int _sptr ;
Click to expand...

Anything starting with an _ is reserved for the compiler. See
http://www.mail-archive.com/[email protected]/msg78723.html , or
http://www.mozilla.org/hacking/portable-cpp.html#no_reserved_names
which quotes the C++ spec, section 17.4.3.1.2. Yes, a whole lot of
existing code violates this. No, this is not flagged as a warning,
though I think it should.

Short summary: you're violating C++ standards with your code
above. As you've already discovered, other names work. Use them.
Don't try to cry conspiracy or "hidden keyword" about _sptr, just do
the right thing and avoid leading underscores.

Nathan Mates
 
Nathan Mates said:
Anything starting with an _ is reserved for the compiler. See
http://www.mail-archive.com/[email protected]/msg78723.html , or
http://www.mozilla.org/hacking/portable-cpp.html#no_reserved_names
which quotes the C++ spec, section 17.4.3.1.2. Yes, a whole lot of
existing code violates this. No, this is not flagged as a warning,
though I think it should.

Short summary: you're violating C++ standards with your code
above. As you've already discovered, other names work. Use them.
Don't try to cry conspiracy or "hidden keyword" about _sptr, just do
the right thing and avoid leading underscores.
Click to expand...

It's still reasonable to ask what the keyword does, especially if the editor
is highlighting "sptr" (no underscore) as a keyword.
 
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