Date: Fri, 28 Mar 2008 17:07:31 +0200 From: Andriy Gapon <avg@icyb.net.ua> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-hackers@freebsd.org, Nate Lawson <nate@root.org> Subject: Re: kobj method signature checking Message-ID: <47ED09B3.9010309@icyb.net.ua> In-Reply-To: <47ED02C5.5090804@icyb.net.ua> References: <47B96989.6070008@icyb.net.ua> <47C918B7.9040504@icyb.net.ua> <47EBCF32.9000705@icyb.net.ua> <200803271408.24684.jhb@freebsd.org> <47ED02C5.5090804@icyb.net.ua>
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on 28/03/2008 16:37 Andriy Gapon said the following: > on 27/03/2008 20:08 John Baldwin said the following: >> On Thursday 27 March 2008 12:45:38 pm Andriy Gapon wrote: >>> on 01/03/2008 10:49 Andriy Gapon said the following: >>>> Here's one strange thing - in your patch you accidentally have >>>> parameters of device_identify switched, I initially inherited that bug >>>> too. I got no error/warning from compiler whatsoever. It wasn't until I >>>> saw that device_get_unit(parent) returned garbage that I my untrained >>>> eye noticed the mistake. >>> As this thread died off I just want to make sure that the above issue is >>> not lost. >>> Maybe we should modify KOBJMETHOD(NAME, FUNC) macro to somehow check >>> FUNC signature/type against the expected signature/type (which is >>> available as NAME##_t)? >> It would be nice if we could do that, yes. >> >>> Maybe something like the following (a bit ugly but I couldn't think of >>> anything better and syntactically correct): >>> { &NAME##_desc, (kobjop_t) (FUNC != (NAME##_t *)NULL ? FUNC : NULL) } >>> >>> This is supposed to produce the following warning if FUNC and NAME##_t >>> have different types: >>> warning: comparison of distinct pointer types lacks a cast >>> >>> The message is also not very descriptive. >> A compile warning/error would be nice though. > > Then the proposed code should be good enough. > That is: > #define KOBJMETHOD(NAME, FUNC) \ > { &NAME##_desc, (kobjop_t) (FUNC != (NAME##_t *)NULL ? FUNC : NULL) } > > BTW, the expression is an obvious NOP and I think that the compiler is > required to calculate constant initializer expressions at compile time, > so binary wise there should not be any incompatibilities too. And the demonstration of the code in work – the following is from 6.3 RELEASE kernel build (plus the above change): /usr/src/sys/dev/acpica/acpi_pcib_acpi.c:109: warning: comparison of distinct pointer types lacks a cast /usr/src/sys/dev/acpica/acpi_pcib_acpi.c:110: warning: comparison of distinct pointer types lacks a cast *** Error code 1 This is because pcib_read_config_t is defined to have several parameters of "u_int" type and acpi_pcib_read_config has "int" for them. Ditto for acpi_pcib_write_config and pcib_write_config_t. -- Andriy Gapon
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