[fpc-devel] Circular references and forward declarations

[Florian Klaempfl]

Jonas Maebe schrieb:
> 
> On 06 Jan 2010, at 13:04, Florian Klaempfl wrote:
> 
>> Jonas Maebe schrieb:
>>>
>>> Another reason is probably to speed up the compilation:
>>> * (re)compiling huge source files can be slow and/or require lots of
>>> memory, depending on the used compiler (and debug information or
>>> optimization settings)
>>
>> For single class c++ files, imo most of the time is spent into reading
>> the huge headers which are often even not needed and a complete mess
>> because nobody has an overview which classes are used and which not.
> 
> It depends. Since these compilers only see whatever is in the current
> source file (and its header files), putting more code in the same source
> file can significantly slow down interprocedural optimizations (as soon
> as one algorithm with quadratic complexity is involved). And inlining
> can significantly increase the complexity of single routines as well,
> making stuff such as register allocation much slower :)

On the other hand keeping things in different files avoids these
optimizations. And being honest: I think using a debug switch set
without any optimization and with maximum checks and fast compilation
should be used for developer builds while wpo, inlining etc. is switched
on during relese builds.