Page Heap doesn't record useful stack infomation?


I'm trying to test a crash scenario (in an isolated test-app) with normal page heap (not full).

I have set up the flags with

gflags /p /enable Test.exe

and I'm overwriting an integer buffer by one element

const size_t s = 100;
vector<int> v1(s, 0);
int* v1_base = &v1[0];
write_to_memory_int(v1_base, s+1);

and indeed when the block is freed in the vectors d'tor, I get a break. The callstack for the break is reported correctly:

0:005> kp
  *** Stack trace for last set context - .thread/.cxr resets it
ChildEBP RetAddr  
0785faa4 11229df2 verifier!VerifierStopMessage+0x1f8
0785fb08 1122a22a verifier!AVrfpDphReportCorruptedBlock+0x1c2
0785fb64 1122a742 verifier!AVrfpDphCheckNormalHeapBlock+0x11a
0785fb84 112290d3 verifier!AVrfpDphNormalHeapFree+0x22
0785fba8 77951564 verifier!AVrfDebugPageHeapFree+0xe3
0785fbf0 7790ac29 ntdll!RtlDebugFreeHeap+0x2f
0785fce4 778b34a2 ntdll!RtlpFreeHeap+0x5d
0785fd04 750c14dd ntdll!RtlFreeHeap+0x142
0785fd18 71fc4c39 kernel32!HeapFree+0x14
0785fd64 00404b0a msvcr80!free(void * pBlock = 0x0726f7b8)+0xcd [f:\dd\vctools\crt_bld\self_x86\crt\src\free.c @ 110]
0785fd90 00402ac7 Test!std::vector<int,std::allocator<int> >::_Tidy

However, when I look at the faulting allocation, I only get this:

0:005> !heap -p -a 0x0726f7b8
    address 0726f7b8 found in
    _HEAP @ 30000
      HEAP_ENTRY Size Prev Flags    UserPtr UserSize - state
        0726f790 0039 0000  [00]   0726f7b8    00190 - (busy)
        1122a6a7 verifier!AVrfpDphNormalHeapAllocate+0x000000d7
        11228f6e verifier!AVrfDebugPageHeapAllocate+0x0000030e
        77950d96 ntdll!RtlDebugAllocateHeap+0x00000030
        7790af0d ntdll!RtlpAllocateHeap+0x000000c4
        778b3cfe ntdll!RtlAllocateHeap+0x0000023a

that is, there is an allocation stack trace, but it stops at RtlAllocateHeap which is oviously totally useless.

Looking at the stack trace in memory:



0:005> dds 0x03e556f4
03e556f4  00000000
03e556f8  00002050
03e556fc  00050000
03e55700  1122a6a7 verifier!AVrfpDphNormalHeapAllocate+0xd7
03e55704  11228f6e verifier!AVrfDebugPageHeapAllocate+0x30e
03e55708  77950d96 ntdll!RtlDebugAllocateHeap+0x30
03e5570c  7790af0d ntdll!RtlpAllocateHeap+0xc4
03e55710  778b3cfe ntdll!RtlAllocateHeap+0x23a
03e55714  00000000
03e55718  00003001
03e5571c  0004005e

It appears that there isn't in fact anything more recorded.

How can I fix Page Heap to record useful stack traces?

Note that the Test project is not compiled with FPO (/Oy), and I would not have expected to have RtlAllocateHeapbe affected by FPO?

Update: I checked the FPO-ness of the call in question by stepping into the allocation manually (see below) and it would appear that both malloc as well as op new of the VC80(VS2005) runtime libs have some form of FPO enabled ... so maybe that's messing up the stack trace for the stack DB of page heap.

0:004> kv
ChildEBP RetAddr  Args to Child              
077efa7c 77c8af0d 05290000 01001002 00000190 ntdll!RtlDebugAllocateHeap+0x16 (FPO: [Non-Fpo])
077efb60 77c33cfe 00000190 00000000 00000000 ntdll!RtlpAllocateHeap+0xc4 (FPO: [Non-Fpo])
077efbe4 72344d83 05290000 01001002 00000190 ntdll!RtlAllocateHeap+0x23a (FPO: [Non-Fpo])
077efc04 62f595ee 00000190 00000000 00000000 MSVCR80!malloc+0x7a (FPO: [1,0,0]) (CONV: cdecl) 
077efc1c 00406a44 00000190 ebecf74f 00000001 MFC80U!operator new+0x2f (FPO: [Uses EBP] [1,0,0]) (CONV: cdecl)
077efc48 00405479 00000064 00000000 3fffffff Test!std::_Allocate<ATL::CStringT<wchar_t,StrTraitMFC_DLL<wchar_t,ATL::ChTraitsCRT<wchar_t> > > >+0x84 (FPO: [Non-Fpo]) (CONV: cdecl)
077efcb8 004049f4 00000064 ebecf68f 00000000 Test!std::vector<unsigned int,std::allocator<unsigned int> >::_Buy+0x69 (FPO: [Non-Fpo]) (CONV: thiscall)
077efd88 00402a4f 00000064 077efdc0 ebecf44b Test!std::vector<int,std::allocator<int> >::_Construct_n+0x44 (FPO: [Non-Fpo]) (CONV: thiscall)
077eff4c 72342848 00000000 ebec8474 00000000 Test!crashFN+0x35f (FPO: [Non-Fpo]) (CONV: cdecl) 
077eff84 723428c8 75da33aa 072ab3d8 077effd4 MSVCR80!_callthreadstart+0x1b (FPO: [Non-Fpo]) (CONV: cdecl)
077eff88 75da33aa 072ab3d8 077effd4 77c39f72 MSVCR80!_threadstart+0x5a (FPO: [1,0,0]) (CONV: stdcall)
077eff94 77c39f72 072ab3d8 70fca8b2 00000000 kernel32!BaseThreadInitThunk+0xe (FPO: [Non-Fpo])
077effd4 77c39f45 7234286e 072ab3d8 00000000 ntdll!__RtlUserThreadStart+0x70 (FPO: [Non-Fpo])
077effec 00000000 7234286e 072ab3d8 00000000 ntdll!_RtlUserThreadStart+0x1b (FPO: [Non-Fpo])

asked on Stack Overflow Sep 26, 2013 by Martin Ba • edited Sep 27, 2013 by Martin Ba

1 Answer


Thanks to @Marc Sherman for pointing out in the comments that I should check out the real allocation stack trace.

As already edited into the question, VC80(VS2005) is the problem here, as it's CRT has FPO enabled, as seen in the stack trace:

MSVCR80!malloc+0x7a (FPO: [1,0,0]) (CONV: cdecl) 
MFC80U!operator new+0x2f (FPO: [Uses EBP] [1,0,0]) (CONV: cdecl)

Now, having an anchor to search, we find the following:

Why does every heap trace in UMDH get stuck at “malloc”?

Adding a few quotes:

In particular, it would appear that the default malloc implementation on the static link CRT on Visual C++ 2005 not only doesn’t use a frame pointer, but it trashes ebp as a scratch register ...

What does this all mean? Well, anything using malloc that’s built with Visual C++ 2005 won’t be diagnosable with UMDH or anything else that relies on ebp-based stack traces, at least not on x86 builds.

There is also a reply in the comments that's got nice info:

Mark Roberts [MSFT] says: February 25, 2008 at 3:03 pm


Enabling FPO for the 8.0 CRT was not deliberate. The Visual Studio 2008 CRT (9.0) does NOT have FPO enabled, and UMDH should function normally.

For 8.0, an alternative to UMDH would be to use LeakDiag. LeakDiag will actually instrument memory allocators to obtain stack traces. This makes it more versatile than UMDH as it can hook several different allocator types at different granularities (Ranging from the c runtime to raw virtual memory allocations).

By default, LeakDiag simply walks the stack base pointers, but it can be modified to use the Dbghlp StackWalkAPI to resolve FPO data. This will produce full stacks, though the performance penalty is higher. On the flip side, you can customize the stack walking behavior to only go to a certain depth, etc to minimize the perf penalty.

Please find LeakDiag here:

answered on Stack Overflow Sep 27, 2013 by Martin Ba • edited Sep 27, 2013 by EdChum

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