Studio 10 cannot display lex code?

Question

I am evaluating Studio 10 for a large C/C++ application which contains some scanners written with lex. I noticed that the debugger refuses to show code in lex sourcefiles (i.e. files with extension .l which are processed with lex to produce, for example, C files like lex.yy.c).
When I try to step from C code into a function defined in a lex source file, the stack display shows the function, but the source pane stays at the line where the function is invoked. This makes debugging lex generated scanners almost impossible.
This definitely works with Forte 6 Update 2 (I just checked).
Any idea how to make this work again?
I can, if necessary, provide a small example which shows the
problem.

Answer 1

Thanks for the clarification. In the meantime, I found out that this boils
down to the fact that the IDE only accepts a certain list of file extensions for C/C++ files. Because ".lex" is not among these, the editor apparently refuses to display the code.
Unfortunately, this list is fixed and can not be extended (although the
documentation suggests that it is possible to change lists of "mime types and edxtensions").
I renamed a lex testfile to have extension ".c", and then the code displays. This is, however, no viable solution (users don't want to rename large numbers of files because a IDE is , well, restricted).
I doublechecked with another situation: we have also include files with inline definitions, and these files have the extension ".icc", and this poses the same problems: I can't step through these functions. A mechanism to extend this builtin extension list is definitely needed for us.