Messages in this thread |  | | | Date | Wed, 23 Nov 2011 16:37:56 -0800 | | From | David Daney <> | | Subject | Re: [PATCH v3 0/2] Stop some of the abuse of BUG() where compile time checks should be used. |
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On 11/23/2011 03:57 PM, Linus Torvalds wrote: > Btw, would it possibly make sense to make the string more useful? > > For example using __FILE__ and __LINE__, or possibly letting the user > of the BUILD_BUG() give a string ("Using HMASK without > CONFIG_HUGEPAGE").
We thought about doing that, but without doing some complex preprocessor fu, the GCC attribute ((error())) thing doesn't do what we want.
It appears that if more than a single instance of the construct is used in a compilation unit, the string emitted by the compiler for any of the violations will be the last string encountered.
So if you did something like:
. . . Line 99: BUILD_BUG("You failed on line 99"); . . . . Line 666: BUILD_BUG("You failed on line 666"); . . .
The message emitted for a failure at line 99 would be "You failed on line 666". Which is probably worse than no message at all.
It may be possible to do something like:
#define _LINENAME_CONCAT( _name_, _line_ ) _name_##_line_ #define _LINENAME(_name_, _line_) _LINENAME_CONCAT(_name_,_line_)
#define _BUILD_BUG(MSG,FUBAR) \ do { \ extern void FUBAR (void) \ __linktime_error("BUILD_BUG failed: " MSG); \ FUBAR (); \ } while (0) #define BUILD_BUG(M,A) _BUILD_BUG(M, _LINENAME(__build_bug_failed,__LINE__))
But it didn't seem worth it.
> > Whatever. It's bikeshedding - what would probably be more important > would be to get this into linux-next so that we find out whether there > are any compile issues with it on other platforms or compiler > versions. > > Linus >
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