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所以我正在調試我的DPLL實現，它不是很好，所以我在調試器中逐行執行代碼，它得到一個返回語句，但事情是它不會返回，它只是繼續執行相同的功能。 WTF我想，我真的看到了嗎？所以我看了一下disassembly，肯定有一個返回語句跳到了錯誤的地方。從來沒有見過VS生成不正確的代碼，所以我想知道如果我搞砸了某處，但我找不到任何東西。即使在關閉所有優化的情況下編譯，跳轉也不正確。是Visual C++實際上生成公然不正確的代碼？
這說明發生了什麼。
bool dpll(std::vector<clause> f)
{
unitPropagate(f);
if(checkFalseClause(f))
{
return false; //je dpll+5Fh (0C01D1Fh) <-- Totally wrong jump adress
}
else if(checkAllClausesTrue(f))
{
return true; //jmp dpll+206h (0C01EC6h) <-- this is fine
}
else
{
atom l = chooseLiteral(f); //this is where the jump ends up (0C01D1Fh)
std::vector<clause> a = makeDuplicate(f);
replaceInstancesOf(a, l, true);
std::vector<clause> b = makeDuplicate(f);
replaceInstancesOf(b, l, false);
return dpll(a) | dpll(b);
}
//this is where the jump is supposed to go (0C01EC6h)
}
所以我的問題是，Visual Studio是真的打破了還是我誤解了一些東西？有沒有人遇到過這樣的事情？
該版本是Visual Studio Enterprise 2015，如果這有所作爲，代碼將爲x86_32生成。
下面是完整的dissasembly如果任何人的興趣：
00C01CC0 push ebp
00C01CC1 mov ebp,esp
00C01CC3 push 0FFFFFFFFh
00C01CC5 push 0C08FF0h
00C01CCA mov eax,dword ptr fs:[00000000h]
00C01CD0 push eax
00C01CD1 sub esp,40h
00C01CD4 mov eax,dword ptr [__security_cookie (0C0D008h)]
00C01CD9 xor eax,ebp
00C01CDB mov dword ptr [ebp-10h],eax
00C01CDE push ebx
00C01CDF push esi
00C01CE0 push eax
00C01CE1 lea eax,[ebp-0Ch]
00C01CE4 mov dword ptr fs:[00000000h],eax
bool dpll(std::vector<clause> f)
00C01CEA lea ecx,[f]
00C01CED mov dword ptr [ebp-4],0
00C01CF4 call unitPropagate (0C01950h)
{
unitPropagate(f);
00C01CF9 lea ecx,[f]
00C01CFC call checkFalseClause (0C01660h)
00C01D01 test al,al
00C01D03 je dpll+4Ch (0C01D0Ch)
00C01D05 xor bh,bh
00C01D07 jmp dpll+206h (0C01EC6h)
if(checkFalseClause(f))
{
return false;
00C01D0C lea ecx,[f]
00C01D0F call checkAllClausesTrue (0C014F0h)
00C01D14 test al,al
00C01D16 je dpll+5Fh (0C01D1Fh)
}
else if(checkAllClausesTrue(f))
00C01D18 mov bh,1
00C01D1A jmp dpll+206h (0C01EC6h)
{
return true;
}
else
00C01D1F lea edx,[f]
00C01D22 lea ecx,[l]
00C01D25 call chooseLiteral (0C013D0h)
00C01D2A mov byte ptr [ebp-4],1
{
atom l = chooseLiteral(f);
00C01D2E lea edx,[f]
00C01D31 xorps xmm0,xmm0
00C01D34 mov dword ptr [ebp-20h],0
00C01D3B lea ecx,[a]
00C01D3E movq mmword ptr [a],xmm0
00C01D43 call makeDuplicate (0C01A30h)
00C01D48 mov byte ptr [ebp-4],2
00C01D4C sub esp,20h
00C01D4F mov esi,esp
00C01D51 mov bl,1
00C01D53 mov dword ptr [ebp-4Ch],esi
00C01D56 lea ecx,[esi+4]
00C01D59 mov al,byte ptr [l]
00C01D5C mov byte ptr [esi],al
00C01D5E mov dword ptr [ecx+14h],0Fh
00C01D65 mov dword ptr [ecx+10h],0
00C01D6C cmp dword ptr [ecx+14h],10h
00C01D70 jb dpll+0B6h (0C01D76h)
00C01D72 mov eax,dword ptr [ecx]
00C01D74 jmp dpll+0B8h (0C01D78h)
00C01D76 mov eax,ecx
00C01D78 push 0FFFFFFFFh
00C01D7A mov byte ptr [eax],0
00C01D7D lea eax,[ebp-44h]
00C01D80 push 0
00C01D82 push eax
00C01D83 call std::basic_string<char,std::char_traits<char>,std::allocator<char> >::assign (0C02A80h)
00C01D88 mov al,byte ptr [ebp-2Ch]
00C01D8B lea ecx,[a]
00C01D8E mov byte ptr [esi+1Ch],al
00C01D91 mov dl,bl
00C01D93 mov al,byte ptr [ebp-2Bh]
00C01D96 mov byte ptr [esi+1Dh],al
00C01D99 call replaceInstancesOf (0C017D0h)
00C01D9E xorps xmm0,xmm0
00C01DA1 mov dword ptr [ebp-14h],0
std::vector<clause> a = makeDuplicate(f);
replaceInstancesOf(a, l, true);
00C01DA8 lea edx,[f]
std::vector<clause> a = makeDuplicate(f);
replaceInstancesOf(a, l, true);
00C01DAB movq mmword ptr [b],xmm0
00C01DB0 lea ecx,[b]
00C01DB3 call makeDuplicate (0C01A30h)
00C01DB8 mov esi,esp
00C01DBA mov byte ptr [ebp-4],3
00C01DBE mov dword ptr [ebp-4Ch],esi
00C01DC1 lea ecx,[esi+4]
00C01DC4 mov al,byte ptr [l]
00C01DC7 xor bl,bl
00C01DC9 push 0FFFFFFFFh
00C01DCB mov byte ptr [esi],al
00C01DCD lea eax,[ebp-44h]
00C01DD0 push 0
00C01DD2 mov dword ptr [ecx+14h],0Fh
00C01DD9 mov dword ptr [ecx+10h],0
00C01DE0 push eax
00C01DE1 mov byte ptr [ecx],bl
00C01DE3 call std::basic_string<char,std::char_traits<char>,std::allocator<char> >::assign (0C02A80h)
00C01DE8 mov al,byte ptr [ebp-2Ch]
00C01DEB lea ecx,[b]
00C01DEE mov byte ptr [esi+1Ch],al
00C01DF1 mov dl,bl
00C01DF3 mov al,byte ptr [ebp-2Bh]
00C01DF6 mov byte ptr [esi+1Dh],al
00C01DF9 call replaceInstancesOf (0C017D0h)
std::vector<clause> b = makeDuplicate(f);
replaceInstancesOf(b, l, false);
00C01DFE add esp,14h
00C01E01 lea eax,[a]
00C01E04 mov ecx,esp
00C01E06 push eax
00C01E07 call std::vector<std::vector<atom,std::allocator<atom> >,std::allocator<std::vector<atom,std::allocator<atom> > > >::vector<std::vector<atom,std::allocator<atom> >,std::allocator<std::vector<atom,std::allocator<atom> > > > (0C02420h)
00C01E0C call dpll (0C01CC0h)
00C01E11 mov bl,al
00C01E13 mov ecx,esp
00C01E15 lea eax,[b]
00C01E18 push eax
00C01E19 call std::vector<std::vector<atom,std::allocator<atom> >,std::allocator<std::vector<atom,std::allocator<atom> > > >::vector<std::vector<atom,std::allocator<atom> >,std::allocator<std::vector<atom,std::allocator<atom> > > > (0C02420h)
00C01E1E call dpll (0C01CC0h)
00C01E23 mov ecx,dword ptr [b]
00C01E26 mov bh,al
00C01E28 add esp,0Ch
00C01E2B or bh,bl
00C01E2D test ecx,ecx
00C01E2F je dpll+1B4h (0C01E74h)
00C01E31 push dword ptr [ebp-4Ch]
00C01E34 mov edx,dword ptr [ebp-18h]
00C01E37 push ecx
00C01E38 call std::_Destroy_range1<std::allocator<std::vector<atom,std::allocator<atom> > >,std::vector<atom,std::allocator<atom> > *> (0C035E0h)
00C01E3D mov ecx,dword ptr [ebp-14h]
00C01E40 mov eax,2AAAAAABh
00C01E45 mov esi,dword ptr [b]
00C01E48 add esp,8
00C01E4B sub ecx,esi
00C01E4D imul ecx
00C01E4F sar edx,1
00C01E51 mov eax,edx
00C01E53 shr eax,1Fh
00C01E56 add eax,edx
00C01E58 push eax
00C01E59 push esi
00C01E5A call std::_Wrap_alloc<std::allocator<std::vector<atom,std::allocator<atom> > > >::deallocate (0C02D20h)
00C01E5F mov dword ptr [b],0
00C01E66 mov dword ptr [ebp-18h],0
00C01E6D mov dword ptr [ebp-14h],0
00C01E74 mov ecx,dword ptr [a]
00C01E77 test ecx,ecx
00C01E79 je dpll+1FEh (0C01EBEh)
00C01E7B push dword ptr [ebp-4Ch]
00C01E7E mov edx,dword ptr [ebp-24h]
00C01E81 push ecx
00C01E82 call std::_Destroy_range1<std::allocator<std::vector<atom,std::allocator<atom> > >,std::vector<atom,std::allocator<atom> > *> (0C035E0h)
00C01E87 mov ecx,dword ptr [ebp-20h]
00C01E8A mov eax,2AAAAAABh
00C01E8F mov esi,dword ptr [a]
00C01E92 add esp,8
00C01E95 sub ecx,esi
00C01E97 imul ecx
00C01E99 sar edx,1
00C01E9B mov eax,edx
00C01E9D shr eax,1Fh
00C01EA0 add eax,edx
00C01EA2 push eax
00C01EA3 push esi
00C01EA4 call std::_Wrap_alloc<std::allocator<std::vector<atom,std::allocator<atom> > > >::deallocate (0C02D20h)
00C01EA9 mov dword ptr [a],0
00C01EB0 mov dword ptr [ebp-24h],0
00C01EB7 mov dword ptr [ebp-20h],0
00C01EBE lea ecx,[ebp-44h]
00C01EC1 call std::basic_string<char,std::char_traits<char>,std::allocator<char> >::~basic_string<char,std::char_traits<char>,std::allocator<char> > (0C027A0h)
00C01EC6 mov ecx,dword ptr [f]
00C01EC9 test ecx,ecx
00C01ECB je dpll+23Bh (0C01EFBh)
00C01ECD push dword ptr [ebp-4Ch]
00C01ED0 mov edx,dword ptr [ebp+0Ch]
00C01ED3 push ecx
00C01ED4 call std::_Destroy_range1<std::allocator<std::vector<atom,std::allocator<atom> > >,std::vector<atom,std::allocator<atom> > *> (0C035E0h)
00C01ED9 mov ecx,dword ptr [ebp+10h]
00C01EDC mov eax,2AAAAAABh
00C01EE1 mov esi,dword ptr [f]
00C01EE4 add esp,8
00C01EE7 sub ecx,esi
00C01EE9 imul ecx
00C01EEB sar edx,1
00C01EED mov ecx,edx
00C01EEF shr ecx,1Fh
00C01EF2 add ecx,edx
00C01EF4 push ecx
00C01EF5 push esi
00C01EF6 call std::_Wrap_alloc<std::allocator<std::vector<atom,std::allocator<atom> > > >::deallocate (0C02D20h)
00C01EFB mov al,bh
00C01EFD mov ecx,dword ptr [ebp-0Ch]
00C01F00 mov dword ptr fs:[0],ecx
00C01F07 pop ecx
00C01F08 pop esi
00C01F09 pop ebx
00C01F0A mov ecx,dword ptr [ebp-10h]
00C01F0D xor ecx,ebp
00C01F0F call __security_check_cookie (0C080CCh)
00C01F14 mov esp,ebp
00C01F16 pop ebp
00C01F17 ret
神祕縮寫？ DPLL？ – zipzit
可能是未定義的行爲。允許編譯器進行優化，假設未定義的東西不會發生，從而可能導致各種瘋狂的事情。 – NathanOliver
0C01D1Fh實際上是在'if（checkAllClausesTrue（f））'之前。如果只是源與組件錯誤交錯。 – Groo