[fpc-pascal] Re: [Bulk] Re: Namespaces Support

[Marcos Douglas]

On Fri, Nov 1, 2013 at 11:54 PM, Dmitry Boyarintsev
<skalogryz.lists at gmail.com> wrote:
> Technical problem:
> * a unit name collision of two independent library code. Either library are
> using unit with the same name. The code in the conflicting units is
> different. Thus one library should use its own unit, the other should use
> its own.
> Since FPC allows to specify the search path for the whole compiled program,
> the second library used, will be using a wrong unit (from the first
> library), causing either compilation to fail or wrong code generated;
>
> Can anyone think of any logical problems with this feature:
> * allow any unit (or units under specified directories) to use their own
> "unit-search" paths, than defined for the project. In that case if a library
> has its own unit, the compiler will be using the library specific unit (by
> finding it in the library specific search path).
>
> From compiler point of view - it's only a matter of where to find the source
> code for the unit and how to name the resulting objects and object file.
> (names must not conflict, in case some units of a compiler project match);
> Linker, shouldn't have any issues as long as objects files were created
> properly;
> Debugging information - no problems here, since the source file name is
> specified explicitly and is typically full path;
>
> Limitations:
> * two units with the same name are not allowed to be used by any other unit
> at the same time
> uses unitA (from pathA), unitA (from pathB)  - not allowed;
> * RTTI collisions are not to be resolved by this feature;

Complex...

Think this:
/project/unit1.pas
/project/StrUtils.pas
/lib/StrUtils.pas

===code===
unit unit1;

uses StrUtils; // local or Lib???
===code===

To compile the unit1.pas the compiler need to know where is
StrUtils.pas and whether to use /lib/StrUtils or /project/StrUtils,
right?
So, if we could to set a parameter to compiler saying:
fpc -ALIAS /lib/* TheLib

Of course I invented the "-ALIAS" parameter.
So, returning to unit1, if we want to use the "local" StrUtils unit,
just use the name "StrUtils". But if we want to use the Lib's
StrUtils, then:

===code===
unit unit1;

uses TheLib.StrUtils;
===code===

What do you think?

Best regards,
Marcos Douglas