Date: Tue, 18 Apr 1995 15:08:34 -0400 From: Garrett Wollman <wollman@halloran-eldar.lcs.mit.edu> To: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com> Cc: current@FreeBSD.org Subject: Memory fill patterns Message-ID: <9504181908.AA00747@halloran-eldar.lcs.mit.edu> In-Reply-To: <199504152313.QAA05625@gndrsh.aac.dev.com> References: <636.797979286@freefall.cdrom.com> <199504152313.QAA05625@gndrsh.aac.dev.com>
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<<On Sat, 15 Apr 1995 16:13:00 -0700 (PDT), "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com> said: > We have lots of choices, a grep of /usr/share/dict/words turns > up 64 words that are 8 characters long using the letters [a-filo]. You > use 1 for i and l and 0 for o: [list deleted] Unfortunately, Rod missed the point, or rather, he saw one of them and missed the rest. Here is the rationale for the choice of 0xdeadbeef (or 0xdeadbee1): 1) When printed in decimal, it's obnoxiously large and negative. 2) When printed in hex, It's recognizable. 3) When printed as a float, it's either invalid or at least obnoxiously large. 4) When used as an address, it's unlikely to be mapped. 5) When used as an address, it will cause an unaligned-access trap. This is from memory after someone posted in alt.folklore.computers three or four years ago about the origin of 0xdeadbee1. -GAWollman -- Garrett A. Wollman | Shashish is simple, it's discreet, it's brief. ... wollman@lcs.mit.edu | Shashish is the bonding of hearts in spite of distance. Opinions not those of| It is a bond more powerful than absence. We like people MIT, LCS, ANA, or NSA| who like Shashish. - Claude McKenzie + Florent Vollant
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