[Patch,Fortran] PR39427/37829 - implement F2003's constructors

[Tobias Burnus]

I would like to *ping*.

Additionally, I attached an updated patch as the tree-walking patch is 
now in. The updated patch is also available at 
https://userpage.physik.fu-berlin.de/~tburnus/tmp/constructor.diff


On 11/06/2011 04:29 PM, Tobias Burnus wrote:
> this patch fixes as collateral effect PR 37829 (alias PR 45190) where 
> C_PTR/C_FUNPTR occurred when use associating a module using them, if 
> one additionally uses iso_fc_binding directly.
>
> The main part of this patch, however, is for PR 39427 (alias 45190): 
> Allowing generic functions to have the same name as a derived type, 
> which is a Fortran 2003 feature. In expressions, the generic functions 
> have a higher precedence then the structure constructor. Note that the 
> functions are not required to return the derived type.
>
> This feature allows one to create something which looks similar to 
> constructors in other OOP languages, except that static constructor 
> functions do not exist.
>
> This patch implements them by creating for each derived type two 
> symbols (symtrees): One for the derived type and one for the generic 
> function, which links to the derived type. To distinguish them, the 
> derived type starts with a capital letter in the symtree. In order to 
> facilitate the error-message handling, the symbol itself remains in 
> lower case.
>
> The main challenges were to ensure that one gets the derived type when 
> needed and to store them properly in the module. The most time 
> consuming part was to find all the places one had to change that 
> issues with module reading could turn up much later; for instance at 
> resolution time of a scope which had read that module. In total, it 
> took 18 months between the first draft patch (cf. PR39427 comment 6, 
> 12-14) and the final patch. Although, the patch looked almost working 
> by then, it took many, many, many hours to fix the issues. Also the 
> RFC patch, posted 6 days ago, had more issues than I had hoped for.
>
> The attached patch had been build on x86-64-linux and successfully 
> regtested (gfortran and libgomp). (A full bootstrap of an almost-ready 
> version was done as well; I had to rebuild because I found some 
> left-over commented code blocks.)
>
> Additionally, I tried the previous patches with several programs to 
> reduce the likelihood that it breaks real-world code. In particular, 
> the very latest version of the patch was used to compile FLEUR, Elk, 
> Octopus and the Polyhedron benchmark. Yesterday evening's version was 
> used to compile the Exciting code (which includes the sensitive FoX 
> Fortran XML library), CP2K, PSBLAS and FGSL. With a slightly older 
> version, I also successfully compiled Tonto, Quantum Espresso and Abinit.
>
> OK for the trunk?
>
> Tobias
>
> PS: I have also included a patch for the website, i.e. 
> http://gcc.gnu.org/gcc-4.7/changes.html#fortran
>
> PPS: As mentioned in the attachment, the patch includes the 
> tree-walking patch, which was posted before. It's a really an 
> independent bug, even if it only exposed with the constructor patch. I 
> can either commit it before or as part of this patch. See also 
> http://gcc.gnu.org/ml/fortran/2011-11/msg00026.html
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