[vtkusers] " " vs < > for includes

[Francois Bertel]

<> :  the compiler looks for header file in the INCLUDE path
"":  the compiler looks in the current directory first, then in the
INCLUDE path.

But this is actually compiler specific. The norm says:

WG14/N843, Committee Draft, section 6.10.2 Source file inclusion, page 136:
ref: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n843.pdf

2 A preprocessing directive of the form
     # include <h-char-sequence> new-line
  searches a sequence of implementation-defined places for a header
identified uniquely by
  the specified sequence between the < and > delimiters, and causes
the replacement of that
  directive by the entire contents of the header. How the places are
specified or the header
  identified is implementation-defined.

3 A preprocessing directive of the form
     # include "q-char-sequence" new-line
  causes the replacement of that directive by the entire contents of
the source file identified
  by the specified sequence between the " delimiters. The named source
file is searched
for in an implementation-defined manner. If this search is not
supported, or if the search
fails, the directive is reprocessed as if it read
    # include <h-char-sequence> new-line
with the identical contained sequence (including > characters, if any)
from the original
directive.


On Thu, Nov 19, 2009 at 10:22 AM, David Doria <daviddoria+vtk at gmail.com> wrote:
> I noticed that most of the includes are done like this:
> #include "vtkPolyData.h"
>
> Don't the quotes mean "look in the current directory", where
> #include <vtkPolyData.h>
>
> means "look on the PATH"?
>
> If this is correct, shouldn't they all use <> since we want to find
> headers in all of the subdirectories (VTK/Graphics, VTK/Filtering,
> etc), which I assume have been put on a header_path type variable by
> cmake?
>
> It clearly works the way it is and I'm sure it is "correct" since the
> whole project does it like this, I was just curious.
>
> David
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-- 
François Bertel, PhD  | Kitware Inc. Suite 204
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