[Bug c/42439] Linux kernel BUILD_BUG_ON() broke

[joseph at codesourcery dot com]

------- Comment #2 from joseph at codesourcery dot com  2009-12-20 01:16 -------
Subject: Re:   New: Linux kernel BUILD_BUG_ON() broke

This is a different sort of not-an-integer-constant-expression from the 
previous cases the kernel was found to use with invalid unevaluated 
operands (I asked in <http://gcc.gnu.org/ml/gcc/2009-04/msg00678.html> if 
it was being used for bit-field widths).

 const int max = [valid expression];
 ((void)(sizeof(struct { int:-!!(max >= (1 << 16)); })));

Here, you are using a const variable in what's meant to be an integer 
constant expression, which is only valid for C++ not C.  Much the same 
workaround as applied for enums in 
<http://gcc.gnu.org/ml/gcc-patches/2009-04/msg02022.html> would probably 
work for this, but it's clearly a different undocumented extension being 
used.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42439