Re: [PATCH] C++ API database

[Ulrich Drepper <drepper@redhat.com>]

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Ping.  Anyone having problems with this?  And the governance of the file?

On Mon, Sep 12, 2022 at 1:51 PM Ulrich Drepper <drepper@redhat.com> wrote:

> After my prior inquiry into the use of python as a build tool for
> maintainers didn't produce any negative comments and several active and
> even enthusiastic support message I'm going forward with submitting the
> patch.
>
> To repeat the detail, for the generation of the upcoming C++ standard
> library module and the hints for missing definitions/declarations in the
> std:: namespace we need a list of standard C++ APIs.  The information
> needed for the two use cases is different but the actual APIs overlap
> almost completely and therefore it would be a bad idea to have the data
> separated.
>
> We could opt for a file format that is easy to read in awk and writing the
> appropriate scripts to transform the data into the appropriate output
> format but this looks ugly, is hard to understand, and a nightmare to
> maintain.  On the other hand, writing the code in Python is simple and
> clean.
>
>
> Therefore, Jonathan and I worked on a CSV file which contains the
> necessary information and a Python to create the gperf input file to
> generate std-name-hint.h and also, in future, the complete source of the
> export interface description for the standard library module.  This mode is
> not yet used because the module support isn't ready yet.  The output file
> corresponds to the hand-coded version of the export code Jonathan uses
> right now.
>
> Note that in both of these cases the generated files are static, they
> don't depend on the local configuration and therefore are checked into the
> source code repository.  The script only has to run if the generated files
> are explicitly removed or, in maintainer mode, if the CSV file has
> changed.  For normal compilation from a healthy source code tree the tool
> is not needed.
>
>
> One remaining issue is the responsibility for the CSV file.  The file
> needs to live in the directory of the frontend and therefore nominally
> changes need to be approved by the frontend maintainers.  The content
> entirely consists of information from the standard library, though.  Any
> change that doesn't break the build on one machine (i.e., the Python script
> doesn't fail) will not course any problem because the output format of the
> script is correct.  Therefore we have been wondering whether the CSV file
> should at least have shared ownership between the frontend maintainers and
> the libstdc++ maintainers.
>
> The CSV file contain more hint information than the old hand-coded .gperf
> file.  So, an additional effect of this patch is the extension of the hints
> that are provided but given that the lookup is now fast this shouldn't have
> any negative impact.  The file is not complete, though, this will come over
> time and definitely before the module support is done.
>
> I build my complete set of compilers with this patch without problems.
>
> Any comments?
>
> 2022-09-12  Jonathan Wakely  <jwakely@redhat.com>
>             Ulrich Drepper  <drepper@redhat.com>
>
> contrib/ChangeLog
>         * gcc_update: Add rule to generate gcc/cp/std-name-hint.gperf.
>
> gcc/cp/ChangeLog
>         * Make-lang.in: Add rule to generate gcc/cp/std-name-hint.gperf.
>         Adjust rule to generate $(srcdir)/cp/std-name-hint.h.
>         Add explicit rule to depend cp/name-lookup.o on
>         $(srcdir)/cp/std-name-hint.h.
>         * cxxapi-data.csv: New file.  Database of C++ APIs.
>         * gen-cxxapi-file.py: New file.  Script to generate source code for
>         C++ standard library exports and to generate C++ std:: namespace
>         fix hints.
>         * std-name-hint.gperf: Regenerated.
>         * std-name-hint.h: Regenerated.
>