Messages in this thread |  | | Subject | Re: [BUG] Bad #define, nonportable C, missing {} | From | Andreas Schwab <> | Date | 21 Nov 2001 12:10:17 +0100 |
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vda <vda@port.imtp.ilyichevsk.odessa.ua> writes:
|> Upon random browsing in the kernel tree I noticed in accel.c: |> *a++ = byte_rev[*a] |> which isn't 100% correct C AFAIK. At least Stroustrup in his C++ book |> warns that this kind of code has to be avoided.
This is definitely causing undefined behaviour. AFAIK, gcc 3.1 (current CVS version) can warn about such errors (-Wsequence-point).
|> ======= bad_c.diff ======= |> diff -u --recursive linux-2.4.13-old/arch/mips/lib/tinycon.c |> linux-2.4.13-new/arch/mips/lib/tinycon.c |> --- linux-2.4.13-old/arch/mips/lib/tinycon.c Thu Jun 26 17:33:37 1997 |> +++ linux-2.4.13-new/arch/mips/lib/tinycon.c Wed Nov 21 00:54:05 2001 |> @@ -83,14 +83,18 @@ |> register int i; |> |> caddr = vram_addr; |> - for(i=0; i<size_x * (size_y-1); i++) |> - *(caddr++) = *(caddr + size_x); |> + for(i=0; i<size_x * (size_y-1); i++) { |> + *caddr = *(caddr + size_x); |> + caddr++; |> + }
Alternatively you can write:
for(i=0; i<size_x * (size_y-1); i++, caddr++) *caddr = *(caddr + size_x);
or even:
for(i=0; i<size_x * (size_y-1); i++, caddr++) *caddr = caddr[size_x];
Andreas.
-- Andreas Schwab "And now for something Andreas.Schwab@suse.de completely different." SuSE Labs, SuSE GmbH, Schanzäckerstr. 10, D-90443 Nürnberg Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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