[pgrouting-dev] duplicate function names in core

[Stephen Woodbridge]

Hello Mario,

On 7/11/2012 3:25 AM, Mario Basa wrote:
> Hello Steve,
>
> With the problem I am encountering when I brought the driving_distance
> into core, both boost_drivedist.cpp and astar_boost_wrapper.cpp have
> graph_add_edge() function and Edge and Vertex structs.
>
> The offending components here are the structs I think since they have
> different values even if they have the same name in the c++ files. So,
> whichever you compile first (astar or drivedist) in the CMAKE file
> will work while the other will core dump. For fun, I made a different
> library in the CMAKE for drivedist, and it still dumped core.

Yes, this could be a problem. I think that this is not a problem if each 
algorithm has its own directory because then the includes and code that 
uses them are all local to the directory. And this eliminates the cross 
contamination.

You still need to public interfaces to be consistent and not 
conflicting. For example, you would not want astar_sp() and drivedist() 
to return different structs using the same name, And you would not want 
to pass a struct or array of struct the is called the same thing but has 
different definitions BECAUSE these are public (ie: global) interfaces 
and redefinition in the global space will break things.

> It was only after I renamed everything (Edge_dd,Vertex_dd, etc.) did
> it work. Again, this is so difficult to debug, well time consuming
> anyway. I am not so familiar with the recent gcc compiler, but I'll
> try look if there is a compile time option to give out warnings for
> similar function names.

Yes, this is very tricky to debug. Great work figuring this out.

> I'll move the common functions into a pgr_utils.h file to take out
> redundancy in core.

Excellent! Thanks for all your time and effort on this.

-Steve

> Mario.
>
>
> On Wed, Jul 11, 2012 at 8:38 AM, Stephen Woodbridge
> <woodbri at swoodbridge.com> wrote:
>> On 7/10/2012 5:23 AM, Mario Basa wrote:
>>>
>>> Hello,
>>>
>>> I am encountering problems placing the drivedist.c and
>>> boost_drivedist.cpp into core (everything compiles, drivedist works
>>> but astar searches dumps core. If I take out drivedist, astar works
>>> like normal.), so I decided to poke around the source. I just found
>>> out that there are so many duplicate functions (i.e.
>>> finish(),text2char(),etc.) and struct names (edge_column,etc.) in each
>>> of the C files.
>>>
>>> Since C does not have any namespace functionality nor function
>>> overloading, I don't have any idea which one will be called whenever
>>> there is a library call. Scary since this will be difficult to debug.
>>>
>>> Now that pgRouting is getting source contributions, I think this will
>>> be a good time that we start discussing function naming conventions to
>>> avoid duplicates as well as directory (core and extensions)
>>> structures.
>>
>>
>> Mario,
>>
>> UGH! Ideally one of two things should happen:
>>
>> 1. common functions with compatible signatures should be extracted into a
>> common.c common.h or utils.c utils.h and get shared by all algorithms that
>> need them.
>>
>> 2. local functions should all be declares "static" which means they are not
>> visible or callable from references outside the file they are declared in.
>>
>> So, if you have a C wrapper and it needs functions and no other files need
>> to use these functions then they should be declared as static and placed in
>> the C wrapper file.
>>
>> If you have some function that multiple C files need to call or you C++ also
>> needs to call, then it needs to go into a file like <namespace>_utils.c and
>> all the functions in this file need to have a unique
>> <namespace>_functionname() like signature.
>>
>> I think this will minimize the changes we need to make to the existing code
>> using "static" declarations for most things, and then moving the others into
>> some namespace'd set of files.
>>
>> How does this sound?
>>
>> I like the idea of having multiple library .so files rather than one huge
>> file because it keeps things separated but more so because it makes it easy
>> to rebuild one library without effecting any of the others. I would like to
>> know that if I change TRSP that there is little to zero change that I can
>> impact the other algorithms.
>>
>> Thank about a production environment where you have pgrouting running on
>> lots of databases and in one database you want to add TRSP. By making it one
>> big library you force a change on all the databases that did not need that
>> change, but if TRSP is in a separate library then all the database that are
>> not using it can be assured to be stable because they did not change. The
>> worsted cases is that the new database with TRSP added to it might be
>> unstable and if there is a collision of files like you describe the cases
>> crashes, it only happens in the new database. Hmmm, maybe it doesn't work
>> this way once the postgresql loads the library. But I don't remember having
>> problems loading multiple libraries.
>>
>> Thoughts?
>>
>> -Steve
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