Re: [Opencxx-users] Use OpenC++ with autoconf / configure

[Grzegorz J. <ja...@ac...>]

Marc Waeckerlin wrote:
> Now I have a C++ compiler executable named "trace", which 
> changes all classes by adding function trace to all member 
> functions.
> 
> If I compile with
>   trace -I /path/to/fntrace -d-include -dfntrace.hxx \
>         -- -o x x.cpp
> instead of
>   g++ -o x x.cpp
> 
> Then my classes in x.cpp print a very verbose function 
> trace.
> 
> Now I have created a huge project with GNU Autotools, so to 
> build it, simply call:
>   ./configure && make
> 
> Question:
> 
> Can I exchange the GNU g++ by my own "trace" without 
> changing a single line in my project?
> 
> Approach:
> 
> The first approach is:
>   CXX="trace -I <path> -d-include -dfntrace.hxx --" \
>     ./configure && make
> 
> But unfortunately configure fails because link options are 
> not passed to the linker, i.e. The following does not work:
>   trace <as-above> -- -o x x.cpp -liberty
> 
> But I get the error message:
>   [MetaclassRegistration...]
>   EXECUTING g++ g++ -I <path> -include fntrace.hxx \
>             -liberty -D__opencxx -E -o conftest.occ \
>             -x c++ conftest.cc
>   g++: -liberty: linker input file unused because \
>                  linking not done
>   EXECUTING g++ g++ -o conftest -g -O2 conftest.ii
> 
>   -> Link errors, because the second, not the first call,
>      must be with -liberty, but the second call is missing
>      the link option. Why?
> 
> Is this a bug or missing feature in OpenC++? I think so.

This is missing feature of Autoconf that does not recognize compilers 
generated by OpenC++ :-)

Seriously, AFAIK OpenC++ was not designed with a goal of being a drop-in 
replacement for any particular compiler.

However, one of goals of OpenC++Core project is to make OpenC++ more 
modular, so that you can seamlesly reuse parts you need (lexer, parser, 
analyzer, translator, metaobject protocol, driver), but replace the one 
that does not suit you (command-line options interpretter).

You may also want to have a look at occ2 script, which duplicates 
funcionality of driver and command-line line options interpretter in 
Python. It should be easier to modify this script than C++ driver to 
obtain drop-in replacement.

Yet another solution is to ./configure with genuine compiler, but later 
use "make CXX='trace ...'".

> Other question:
>   How do I split my homebrew enhanced compiler "trace" into 
> the three common steps: Preprocessing, compiling, linking? 
> I suppose, I only need my own compiler for preprocessing, 
> i.e. to generate x.ii, then for compiling and linking, I 
> can use the normal g++?

Right. Use '-E' command-line option to generated compiler. 'occ2' works 
like this --- the generated compiler is used only for translation, all 
other tasks are run from occ2 script using genuine preproc, genuing 
compiler and genuine linker.

BR
Grzegorz

> 
> Thank you
> Regards
> Marc
> 
> 
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