as pointed out by Tom Fredrik Blenning Klaussen in Gentoo Bug 109792, there is a
minor whitespace error in /usr/include/gnu/stubs.h

simple fix for libc/include/stubs-prologue.h:
 #ifdef _LIBC
- #error Applications may not define the macro _LIBC
+# error Applications may not define the macro _LIBC
 #endif

------- Additional Comment #1 From Roland McGrath 2005-10-23 00:48 -------

That line is not unintentional.  That syntax hides #error from pre-C89 compilers.
There is no bug here.

------- Additional Comment #2 From Tom Fredrik Blenning Klaussen 2005-11-14 09:47 -------

For cases which are willfully non-portable wouldn't it be apropriate to add a
comment line saying so?

The only reason I ever came across this issue was when I was trying to fix some
compiler warnings in a build, and makedepend complained. Had I seen such a
comment when I tried to investigate, there would never have been a bug report.

------- Additional Comment #3 From Ulrich Drepper 2005-12-23 04:09 -------

Those who are qualified to change the files know the reason.