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<body class='hmmessage'><div dir='ltr'>Hm, bug in the C backend maybe? I'll have to compare against m3cg.<BR> <BR> - Jay<br><br> <BR><div><hr id="stopSpelling">From: jay.krell@cornell.edu<br>To: m3devel@elegosoft.com<br>Date: Sun, 22 Sep 2013 03:58:34 +0000<br>Subject: [M3devel] what does it mean to read a UINT8?<br><br>
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<div dir="ltr">It appears that this code:<br><br><br>b := LOOPHOLE(used + info.RegionSize - 1, UNTRACED REF UINT8)^;<br><br><br>generates a read of a full INTEGER, in this case 8 bytes.<br><br><br>Now, I know, I could change it to:<br><br><br>b := LOOPHOLE(used + info.RegionSize - BYTESIZE(INTEGER), UNTRACED REF INTEGER)^;<br><br><br>What were my expectations wrong in the first place?<br><br><br>This code was part of getting stack bounds and it'd read<br>the end of the stack to try to ensure it was correct.<br><br><br>I removed it.<br><br><br>0:000> g<br>(15bc.116c): Access violation - code c0000005 (first chance)<br>First chance exceptions are reported before any exception handling.<br>This exception may be expected and handled.<br>*** WARNING: Unable to verify checksum for cm3.exe<br>cm3!ThreadWin32__GetStackBounds+0x1e8:<br>00000001`3fdf1a78 488b48ff mov rcx,qword ptr [rax-1] ds:00000000`0028<br>ffff=????????????????<br>0:000> r rax<br>rax=0000000000290000<br>0:000> r rsp<br>rsp=000000000028fb60<br>0:000> dv<br> start_L_275 = 0x00000000`00338de0<br> end_L_276 = 0x00000000`00338de8<br> L_501_L_502 = 0n48<br> used_L_272 = 0x00000000`0028f000<br>available_L_273 = 0x00000000`00190000 "--- memory read error at address 0x000000<br>00`00190000 ---"<br> b_L_274 = 0x30 '0'<br> a_L_271 = 0n48<br> info_L_270 = struct TA669C7A1<br> _frame = struct ThreadWin32__GetStackBounds_Frame_t<br>0:000> ?? info_L_270<br>struct TA669C7A1<br> +0x000 BaseAddress : 0x00000000`0028f000 "0???"<br> +0x008 AllocationBase : 0x00000000`00190000 "--- memory read error at addr<br>ess 0x00000000`00190000 ---"<br> +0x010 AllocationProtect : 4<br> +0x014 L_7 : [4] ""<br> +0x018 RegionSize : 0n4096<br> +0x020 State : 0x1000<br> +0x024 Protect : 4<br> +0x028 Type : 0x20000<br> +0x02c L_8 : [4] ""<br>0:000> q<br>quit:<br><br><br> - Jay<br> </div></div> </div></body>
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