Re: dump-translation-unit format

[Ian Lance Taylor <iant at google dot com>]

"Sascha Alexander Jopen" <jopen@gmx.net> writes:

> I'm currently working on the output of gcc/g++ -fdump-translation-unit to do
> source code analysis. I found several references that the internal ast
> should include nodes for for, while and do constructs. But I can't find
> those nodes in the dumped files. Sometimes there are such FOR_STMT nodes
> when I compile large units, but when compiling a small test unit containing
> not much more than a for loop, this loop isn't included in the dump. Instead
> there is a GOTO_EXPR where I would expect the for loop. This holds for other
> loops and conditional expressions as well. All FOR_STMT nodes I encountered
> where not from my custom code, but from templates from system includes.
> 
> Are there any optimizations done on the tree before dumping it, and how can
> I prevent this to get an unoptimized tree? Are there other possibilities to
> get those loop nodes? I need them to check whether function calls are done
> in loops or not. Without the bodies of loops I can get information about
> functions called from other functions using the chain links, but not whether
> they are called within loops.

Which version of gcc are you using?  In mainline
-fdump-translation-unit just dumps the global declarations.  If you
want to see FOR_STMT nodes, you need -fdump-tree-original.  But that
is pretty unsatisfactory these days since for_stmt nodes are not
dumped in a useful way.  And that only happens for C++; for C FOR_STMT
nodes are never generated.


> Another thing I don't understand is the following. This dumped function node
> contains two body definitions, one undefined and one with a proper node
> chain. Is this a dump error or has it special meaning?
> 
> @1639   function_decl    name: @2001    mngl: @2002    type: @2003   
>                          scpe: @812     srcp: char_traits.h:322    
>                          chan: @2004    note: member   accs: pub     
>                          args: @2005    body: undefined 
>                          link: extern   body: @2006
> 
> Maybe someone could help me or point me to other resources.

The tree dump code prints out "body: undefined" for an external
function which is not to be compiled by itself.  But such a function
can still have a body; this will be the case for a C++ inline
function.  This is somewhat confusing.

Ian