[Bug c/38397] New: gcc -E -dD changes the meaning of source

["algrant at acm dot org" <gcc-bugzilla at gcc dot gnu dot org>]

compile with -E -dD:

  enum { A, B };
  #define B A
  #define A B+1
  int x = A;

This will print something like

  enum { A, B };
  #define B A
  #define A B+1
  int x = A+1;

This defines x as 2 instead of 1.  Recycle the output bad in and
x gets bigger and bigger.

Although it doesn't seem to be formally defined that the output
of -E -dD is valid source code equivalent to the original,
the output is presented as if it is.  There are at least two
solutions:

- present the #define and #undef as comments

- suppress macro expansion when -dD is used

The ability to suppress macro expansion is a useful feature in
its own right and could make some sources more readable, when the
intention of -E is simply to flatten the input.


-- 
           Summary: gcc -E -dD changes the meaning of source
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: algrant at acm dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38397