From: Linus Torvalds Date: Wed, 22 Jul 2009 15:49:22 +0000 (-0700) Subject: fbmon: work around compiler bug in gcc-2.4.2 X-Git-Tag: accepted/tizen/common/20141203.182822~15203 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=3730793d457fed79a6d49bae72996d458c8e4f2d;p=platform%2Fkernel%2Flinux-arm64.git fbmon: work around compiler bug in gcc-2.4.2 There's some odd bug in gcc-4.2 where it miscompiles a simple loop whent he loop counter is of type 'unsigned char' and it should count to 128. The compiler will incorrectly decide that a trivial loop like this: unsigned char i, ... for (i = 0; i < 128; i++) { .. is endless, and will compile it to a single instruction that just branches to itself. This was triggered by the addition of '-fno-strict-overflow', and we could play games with compiler versions and go back to '-fwrapv' instead, but the trivial way to avoid it is to just make the loop induction variable be an 'int' instead. Thanks to Krzysztof Oledzki for reporting and testing and to Troy Moure for digging through assembler differences and finding it. Reported-and-tested-by: Krzysztof Oledzki Found-by: Troy Moure Gcc-bug-acked-by: Ian Lance Taylor Cc: stable@kernel.org Signed-off-by: Linus Torvalds --- diff --git a/drivers/video/fbmon.c b/drivers/video/fbmon.c index 5c1a2c0..9ae9cd3 100644 --- a/drivers/video/fbmon.c +++ b/drivers/video/fbmon.c @@ -256,8 +256,8 @@ static void fix_edid(unsigned char *edid, int fix) static int edid_checksum(unsigned char *edid) { - unsigned char i, csum = 0, all_null = 0; - int err = 0, fix = check_edid(edid); + unsigned char csum = 0, all_null = 0; + int i, err = 0, fix = check_edid(edid); if (fix) fix_edid(edid, fix);