Style of libstdc++ header files

[Wolfgang Bangerth <bangerth@ices.utexas.edu>]

libstdc++ and other compiler library header file writers,

the other day I again ploughed for several hours through libstdc++ headers 
trying to reduce a testcase and it occurred to me again that I had always 
meant to share some piece of experience:

When we try to reduce a testcase, we try to strip away large chunks of code. 
This is fairly straightforward for code like this:
  class X {
    void method1 ();
    //...
    void method100 ();
  };

  void X::method1 () {...}
  //...
  void X::method100 () {...}

The reason is this: we try to remove all the definitions of X::method1...100. 
If this succeeds, then fine. If not, then we remove 50-100 and see whether 
the bug is still there, and so on. Note in particular that removing the 
_definition_ of a function can _never_ introduce a new compile-time error, 
since the declaration is still there. Thus, if only method63 is necessary to 
show a particular ICE or compiler error, we're there relatively quickly by 
bisection of the whole block of function definitions.

method63 will then only call a very small number of functions in class X, so 
that I can also bulk delete the declarations of the other methods.

Unfortunately, libstdc++ is, mostly, not written that way: there are a lot of 
definitions of member functions inlined into the class declaration. Now 
consider what happens here:
  class X {
    void method1 () {}
    void method2 () { method1(); }
    void method3 () { method2(); something_else(); }
  };
Assume that the problem happens because method3 tries to do something in 
something_else(). method[12] are not involved at all, and I would like to 
delete their definitions because they use other stuff that I'd like to remove 
as well. Alas, I can't: I can't just bulk delete the entire block 
method1--method2, since method3 calls method2 which in turn calls method2. 
What I need to do is painstakingly edit the contents of the inlined 
definitions of these functions because I can't just delete the entire block 
without also removing the necessary declarations. 

In effect, the work I will have to do is more like linear in the number of 
functions in a class, rather than the previous logarithmic complexity. This 
can be all the difference between a quick 15 minute reduction of a 50kloc 
testcase, or, like yesterday, one that takes the better part of a football 
game transmission (i.e. 2-3 hours).


My request therefore would be if the libstdc++ people could comment if it is 
possible to gradually move away from their style of using inlined function 
definitions, and towards a style where function declarations and definitions 
are always clearly separated. I understand that this is a huge change, but 
one that could make the life of us bugmasters so much easier!

Thanks
 Wolfgang
 
-------------------------------------------------------------------------
Wolfgang Bangerth              email:            bangerth@ices.utexas.edu
                               www: http://www.ices.utexas.edu/~bangerth/