Segfault on GCC 6 release builds

Miss · 2016-12-01T22:01:37

Judging by the disassembly, it seems like it completely excludes this part of the code from the binary and crashes when trying to access member variables. (Because optimization says this can never be nullptr, I suppose?) // Allow call on null pointer if (this == 0) return 0; Crash is on the first mov instruction here: (gdb) disas Dump of assembler code for function asCTypeInfo::CastToObjectType(): => 0x00005555557acc80 <+0>: mov eax,DWORD PTR [rdi+0x30] 0x00005555557acc83 <+3>: test eax,0x2000003 0x00005555557acc88 <+8>: je 0x5555557acca0 <asCTypeInfo::CastToObjectType()+32> 0x00005555557acc8a <+10>: test eax,0x1000000 0x00005555557acc8f <+15>: mov eax,0x0 0x00005555557acc94 <+20>: cmove rax,rdi 0x00005555557acc98 <+24>: ret 0x00005555557acc99 <+25>: nop DWORD PTR [rax+0x0] 0x00005555557acca0 <+32>: xor eax,eax 0x00005555557acca2 <+34>: ret GCC 6 changelist mentions this: Value range propagation now assumes that the this pointer of C++ member functions is non-null. This eliminates common null pointer checks but also breaks some non-conforming code-bases (such as Qt-5, Chromium, KDevelop). As a temporary work-around -fno-delete-null-pointer-checks can be used. Wrong code can be identified by using -fsanitize=undefined.

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Started by Miss November 25, 2016 09:43 AM

10 comments, last by WitchLord 7 years, 11 months ago

dkrusu

386

December 01, 2016 07:29 PM

The changes you made now cause the following error when building on GCC 6.2.0:


../../source/as_callfunc.cpp: In function ‘int PrepareSystemFunction(asCScriptFunction*, asSSystemFunctionInterface*, asCScriptEngine*)’:
../../source/as_callfunc.cpp:489:47: error: ‘class asCTypeInfo’ has no member named ‘CastToObjectType’
    asSTypeBehaviour *beh = &dt.GetTypeInfo()->CastToObjectType()->beh;

Edit: Changing line 489 to the following fixes it


asSTypeBehaviour *beh = &CastToObjectType(dt.GetTypeInfo())->beh;

WitchLord

4,860

December 01, 2016 10:01 PM

Thanks. I'll have it fixed.

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Segfault on GCC 6 release builds

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