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SubjectRe: [PATCH] compiler.h: fix error in BUILD_BUG_ON() reporting
On 3/31/20 5:36 PM, Nathan Chancellor wrote:
> On Tue, Mar 31, 2020 at 05:25:38PM -0500, Daniel Santos wrote:
>> This will break builds using gcc 4.2 and earlier and the expectation was
>> that you don't put two of them on the same line -- not helpful in macros
>> where it all must be on the same line.  Is gcc 4.2 still supported?  If
>> so, I recommend using another macro for the unique number that uses
>> __COUNTER__ if available and __LINE__ otherwise.  This was the decision
>> for using __LINE__ when I wrote the original anyway.
>> Also note that this construct:
>> BUILD_BUG_ON_MSG(0, "I like chicken"); BUILD_BUG_ON_MSG(1, "I don't like
>> chicken");
>> will incorrectly claim that I like chicken.  This is because of how
>> __attribute__((error)) works -- gcc will use the first declaration to
>> define the error message.
>> I couple of years ago, I almost wrote a gcc extension to get rid of this
>> whole mess and just __builtin_const_assert(cond, msg).  Maybe I'll
>> finish that this year.
>> Daniel
> No, GCC 4.6 is the minimum required version and it is highly likely that
> the minimum version of GCC will be raised to 4.8 soon:
> Cheers,
> Nathan

Thank you Nathan.  In that case this is definitely what we want now.

Reviewed-by: Daniel Santos <>


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