Am 25.09.2018 um 14:06 schrieb Arnd Bergmann: > On Tue, Sep 25, 2018 at 1:35 PM Alexander Lochmann > <alexander.lochmann@xxxxxxxxxxxxxx> wrote: >> >> Hi Arnd, >> >> I recently tried to disable the BUG macros on x86-32. I disabled the >> config item in 'General Setup -> Configure standard kernel features >> (expert users) -> BUG() support'. >> However, BUG/BUG_ON is still defined. In the !CONFIG_BUG branch in >> include/asm-generic/bug.h (line 181) the code checks for the existence >> of architecture-specific variants of those macros. >> Since x86 defines its own version of BUG(), line 182 is *not* used. >> In the following, the x86 variant of BUG() is then used to define the >> BUG_ON() macro. >> >> I propose a patch that really disables both macros if the developer >> wants it. >> It undefines the respective x86 variants, and defines both macros as >> 'empty' macros. > > Maybe we should update the documentation instead. Note that the > generic version is using 'while (1)' rather than 'while (0)', so this is > not an empty macro but rather one that does more than the > arch-specific one-instruction version does. > > We don't really want an empty macro any more, this was used in > the past, but causes compile-time warnings and undefined behavior > for no good reason I see. So the documentation of the CONFIG_BUG option is wrong? It currently states that 'Disabling this option eliminates support for BUG and WARN'. Is the current implemention (an endless loop) desired behavior? - Alex > > Arnd > -- Technische Universität Dortmund Alexander Lochmann PGP key: 0xBC3EF6FD Otto-Hahn-Str. 16 phone: +49.231.7556141 D-44227 Dortmund fax: +49.231.7556116 http://ess.cs.tu-dortmund.de/Staff/al
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