[Issue 2318] New: flaw code generation building a function pointer table

[Sivo Schilling]

If you declare FnPtr as  void delegate() then these issues are gone.
This works with both DMD 1.034 and DMD 2.018 on Win XP SP3 but
using phobos instead of Tango/tangobos.


d-bugmail at puremagic.com Wrote:

> http://d.puremagic.com/issues/show_bug.cgi?id=2318
> 
>            Summary: flaw code generation building a function pointer table
>            Product: D
>            Version: 1.034
>           Platform: PC
>         OS/Version: Windows
>             Status: NEW
>           Severity: normal
>           Priority: P2
>          Component: DMD
>         AssignedTo: bugzilla at digitalmars.com
>         ReportedBy: enzo.petrelli at fastwebnet.it
> 
> 
> /***************************
>         OS:                                     Vista SP1
>         Compiler/linker:        Digital Mars D Compiler v1.034
>         Tango/tangobos Lib:     tango-0.99.7-bin-win32-dmd.1.033
>         Compiled with:          dmd -g -debug epfuntbl.d
> 
>         Debug version:
>         Trying to build a table of 5 function pointers out of
>         5 struct members, 1st and 3rd items are uncorrectly
>         asssigned values
> 
>         Release version:
>         A similar but slightly different behaviour is shown.
>         Further, an "Access violation" is raised
> 
>  ***************************/
> 
> import std.cstream;
> 
> alias void function()   FnPtr;
> 
> void initTTest(TTest * pTst)
> {
> //      pTst.pVtbl = cast(void*) pTst.apFnc.ptr;
>         pTst.apFnc[0] = cast(FnPtr) &pTst.func0;
>         pTst.apFnc[1] = cast(FnPtr) &pTst.func1;
>         pTst.apFnc[2] = cast(FnPtr) &pTst.func2;
>         pTst.apFnc[3] = cast(FnPtr) &pTst.func3;
>         pTst.apFnc[4] = cast(FnPtr) &pTst.func4;
> }
> 
> struct TTest
> {
>         void *          pVtbl;
>         FnPtr[5]        apFnc;
> 
>         void func0()
>         {
>                 dout.writefln("func0");
>         }
>         void func1()
>         {
>                 dout.writefln("func1");
>         }
>         void func2()
>         {
>                 dout.writefln("func2");
>         }
>         void func3()
>         {
>                 dout.writefln("func3");
>         }
>         void func4()
>         {
>                 dout.writefln("func4");
>         }
> }
> 
> void main()
> {
>         TTest * pTst = new TTest;
>         initTTest(pTst);
>         for (int iIdx = 0; iIdx < pTst.apFnc.length; ++iIdx)
>                 dout.writefln("item#%d:0x%08X", iIdx, cast(int)
> pTst.apFnc[iIdx]);
>         pTst.apFnc[1]();
>         pTst.apFnc[3]();
>         pTst.apFnc[4]();
> }
> 
> /*
> execution produces:
> 
> item#0:0x019F3FE0
> item#1:0x004020AC
> item#2:0x019F3FE0
> item#3:0x0040215C
> item#4:0x004021B4
> func1
> func3
> func4
> */
> 
> /*
> disassembly shows that wrong code is generated for the 1st and 3rd
> function pointer assignments:
> function address is loaded into a register but the destination is
> written from another one
> 
> 5:    void initTTest(TTest * pTst)
> 00402010   enter       4,0
> 00402014   push        ebx
> 00402015   push        esi
> 00402016   mov         dword ptr [ebp-4],eax
> 6:    {
> 7:    //  pTst.pVtbl = cast(void*) pTst.apFnc.ptr;
> 8:        pTst.apFnc[0] = cast(FnPtr) &pTst.func0;
> 00402019   mov         eax,dword ptr [pTst]
> 0040201C   mov         ecx,offset _D8epfuntbl5TTest5func0MFZv (00402054)
> 00402021   mov         edx,dword ptr [pTst]
> 00402024   mov         dword ptr [edx+4],eax
> 9:        pTst.apFnc[1] = cast(FnPtr) &pTst.func1;
> 00402027   mov         ebx,edx
> 00402029   mov         ecx,offset _D8epfuntbl5TTest5func1MFZv (004020ac)
> 0040202E   mov         dword ptr [edx+8],ecx
> 10:       pTst.apFnc[2] = cast(FnPtr) &pTst.func2;
> 00402031   mov         eax,edx
> 00402033   mov         ecx,offset _D8epfuntbl5TTest5func2MFZv (00402104)
> 00402038   mov         dword ptr [edx+0Ch],eax
> 11:       pTst.apFnc[3] = cast(FnPtr) &pTst.func3;
> 0040203B   mov         esi,edx
> 0040203D   mov         ecx,offset _D8epfuntbl5TTest5func3MFZv (0040215c)
> 00402042   mov         dword ptr [edx+10h],ecx
> 12:       pTst.apFnc[4] = cast(FnPtr) &pTst.func4;
> 00402045   mov         ebx,edx
> 00402047   mov         ecx,offset _D8epfuntbl5TTest5func4MFZv (004021b4)
> 0040204C   mov         dword ptr [edx+14h],ecx
> 13:   }
> 0040204F   pop         esi
> 00402050   pop         ebx
> 00402051   leave
> 00402052   ret
> 00402053   int         3
> */
> 
> 
> -- 
>