为什么在下面详述的场景中，堆栈空间在x64中增加但在x32中使用相同的代码减少？
背景
我们的客户可以使用域语言编写脚本，该语言在运行时使用递归技术解释并在Web服务器上执行。它们可能会在引发异常的脚本中出错，此异常会被捕获并记录。
由于这种递归技术，我们通过检查在解释器执行脚本时使用的堆栈空间来防止堆栈溢出异常，并在我们实际耗尽堆栈之前终止脚本。
在32位模式下，一切运行良好，当脚本编写程序发生错误时生成Exception，记录，堆栈展开，堆栈中剩余的空间增加和脚本很好地终止了。
在64位模式下，一切都不太好，当脚本编写器生成错误Exception时，会记录，堆栈展开，堆栈中剩余的空间减少。这是非常糟糕的，因为如果脚本碰巧使用了大量的堆栈空间并抛出，那么解除堆栈并记录错误本身的行为会导致StackOverflowException隐藏原始异常，软管IIS，并杀死所有的飞行请求（糟糕，非常糟糕，非常糟糕）。
重新创建问题：
这是一个控制台应用程序，它模拟我在生产中使用的代码，并在设置为x64时重新创建问题，并在x32中正常工作。
using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
namespace ConsoleApplication16
{
class Program
{
const Int32 MaxNumberRecursions = 10;
static Int32 _currentRecursionDepth;
static UInt64 _lastSpaceUsed;
static void Main(string[] args)
{
System.Diagnostics.Debug.WriteLine(String.Format("Is64BitProcess = {0}", System.Environment.Is64BitProcess));
try
{
_lastSpaceUsed = GetStackBytesLeft();
RecurseXTimes();
}
catch (Exception e)
{
System.Diagnostics.Debug.WriteLine(e);
}
}
unsafe static void RecurseXTimes()
{
System.Diagnostics.Debug.WriteLine("--> RecurseXTimes()");
ReportStackSpaceUsage();
try
{
_currentRecursionDepth++;
if (_currentRecursionDepth > MaxNumberRecursions)
{
throw new Exception("Please unwind my stack");
}
System.Diagnostics.Debug.WriteLine(String.Format("Adding {0} bytes to stack.", sizeof(SomeDataToUseUpSomeStackSpace)));
SomeDataToUseUpSomeStackSpace someDataToUseUpSomeStackSpace = new SomeDataToUseUpSomeStackSpace();
RecurseXTimes();
}
catch(Exception e)
{
//Do some logging. NOTE taking this "catch" out "fixes" the problem, but I can't do this in prod.
System.Diagnostics.Debug.WriteLine(e.Message);
throw;
}
finally
{
ReportStackSpaceUsage();
System.Diagnostics.Debug.WriteLine("<-- RecurseXTimes()");
}
}
private static void ReportStackSpaceUsage()
{
UInt64 stackUsed = GetStackBytesLeft();
Int64 stackSpaceDelta = (Int64) stackUsed - (Int64) _lastSpaceUsed;
Int64 stackSpaceDeltaAbs = Math.Abs(stackSpaceDelta);
System.Diagnostics.Debug.WriteLine(
String.Format("Stack space left: {0}. Stack Space Delta: {1} {2}",
stackUsed,
stackSpaceDeltaAbs,
stackSpaceDelta < 0 ? "Allocated On Stack" : "Freed from Stack"));
_lastSpaceUsed = stackUsed;
}
static unsafe ulong GetStackBytesLeft()
{
MEMORY_BASIC_INFORMATION stackInfo = new MEMORY_BASIC_INFORMATION();
UIntPtr currentAddr = new UIntPtr(&stackInfo);
int sizeT = VirtualQuery(currentAddr, ref stackInfo, sizeof(MEMORY_BASIC_INFORMATION));
if (sizeT == 0)
{
//No Data Returned
int lastError = Marshal.GetLastWin32Error();
throw new Win32Exception(lastError);
}
UInt64 stackBytesLeft = currentAddr.ToUInt64() - stackInfo.AllocationBase.ToUInt64();
return stackBytesLeft;
}
[DllImport("kernel32.dll", SetLastError = true)]
static extern int VirtualQuery(UIntPtr lpAddress, ref MEMORY_BASIC_INFORMATION lpBuffer, int dwLength);
[StructLayout(LayoutKind.Sequential)]
struct MEMORY_BASIC_INFORMATION
{
public UIntPtr BaseAddress;
public UIntPtr AllocationBase;
public uint AllocationProtect;
public UIntPtr RegionSize;
public uint State;
public uint Protect;
public uint Type;
};
private struct SomeDataToUseUpSomeStackSpace
{
public Int64 a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, a21, a22, a23, a24, a25;
public Int64 b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b11, b12, b13, b14, b15, b16, b17, b18, b19, b20, b21, b22, b23, b24, b25;
public Int64 c0, c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12, c13, c14, c15, c16, c17, c18, c19, c20, c21, c22, c23, c24, c25;
public Int64 d0, d1, d2, d3, d4, d5, d6, d7, d8, d9, d10, d11, d12, d13, d14, d15, d16, d17, d18, d19, d20, d21, d22, d23, d24, d25;
public Int64 e0, e1, e2, e3, e4, e5, e6, e7, e8, e9, e10, e11, e12, e13, e14, e15, e16, e17, e18, e19, e20, e21, e22, e23, e24, e25;
public Int64 f0, f1, f2, f3, f4, f5, f6, f7, f8, f9, f10, f11, f12, f13, f14, f15, f16, f17, f18, f19, f20, f21, f22, f23, f24, f25;
public Int64 g0, g1, g2, g3, g4, g5, g6, g7, g8, g9, g10, g11, g12, g13, g14, g15, g16, g17, g18, g19, g20, g21, g22, g23, g24, g25;
public Int64 h0, h1, h2, h3, h4, h5, h6, h7, h8, h9, h10, h11, h12, h13, h14, h15, h16, h17, h18, h19, h20, h21, h22, h23, h24, h25;
public Int64 i0, i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, i14, i15, i16, i17, i18, i19, i20, i21, i22, i23, i24, i25;
public Int64 j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15, j16, j17, j18, j19, j20, j21, j22, j23, j24, j25;
public Int64 k0, k1, k2, k3, k4, k5, k6, k7, k8, k9, k10, k11, k12, k13, k14, k15, k16, k17, k18, k19, k20, k21, k22, k23, k24, k25;
public Int64 l0, l1, l2, l3, l4, l5, l6, l7, l8, l9, l10, l11, l12, l13, l14, l15, l16, l17, l18, l19, l20, l21, l22, l23, l24, l25;
public Int64 m0, m1, m2, m3, m4, m5, m6, m7, m8, m9, m10, m11, m12, m13, m14, m15, m16, m17, m18, m19, m20, m21, m22, m23, m24, m25;
public Int64 n0, n1, n2, n3, n4, n5, n6, n7, n8, n9, n10, n11, n12, n13, n14, n15, n16, n17, n18, n19, n20, n21, n22, n23, n24, n25;
public Int64 o0, o1, o2, o3, o4, o5, o6, o7, o8, o9, o10, o11, o12, o13, o14, o15, o16, o17, o18, o19, o20, o21, o22, o23, o24, o25;
public Int64 p0, p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12, p13, p14, p15, p16, p17, p18, p19, p20, p21, p22, p23, p24, p25;
public Int64 q0, q1, q2, q3, q4, q5, q6, q7, q8, q9, q10, q11, q12, q13, q14, q15, q16, q17, q18, q19, q20, q21, q22, q23, q24, q25;
public Int64 r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15, r16, r17, r18, r19, r20, r21, r22, r23, r24, r25;
public Int64 s0, s1, s2, s3, s4, s5, s6, s7, s8, s9, s10, s11, s12, s13, s14, s15, s16, s17, s18, s19, s20, s21, s22, s23, s24, s25;
public Int64 t0, t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16, t17, t18, t19, t20, t21, t22, t23, t24, t25;
public Int64 u0, u1, u2, u3, u4, u5, u6, u7, u8, u9, u10, u11, u12, u13, u14, u15, u16, u17, u18, u19, u20, u21, u22, u23, u24, u25;
public Int64 v0, v1, v2, v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14, v15, v16, v17, v18, v19, v20, v21, v22, v23, v24, v25;
public Int64 w0, w1, w2, w3, w4, w5, w6, w7, w8, w9, w10, w11, w12, w13, w14, w15, w16, w17, w18, w19, w20, w21, w22, w23, w24, w25;
public Int64 x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15, x16, x17, x18, x19, x20, x21, x22, x23, x24, x25;
public Int64 y0, y1, y2, y3, y4, y5, y6, y7, y8, y9, y10, y11, y12, y13, y14, y15, y16, y17, y18, y19, y20, y21, y22, y23, y24, y25;
public Int64 z0, z1, z2, z3, z4, z5, z6, z7, z8, z9, z10, z11, z12, z13, z14, z15, z16, z17, z18, z19, z20, z21, z22, z23, z24, z25;
}
}
}
示例输出：
x32 - 一切都很花哨，堆栈空间减少，下降，并在展开时增加。
Is64BitProcess = False
--> RecurseXTimes()
Stack space left: 1036512. Stack Space Delta: 5652 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 1031004. Stack Space Delta: 5508 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 1025496. Stack Space Delta: 5508 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 1019988. Stack Space Delta: 5508 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 1014480. Stack Space Delta: 5508 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 1008972. Stack Space Delta: 5508 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 1003464. Stack Space Delta: 5508 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 997956. Stack Space Delta: 5508 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 992448. Stack Space Delta: 5508 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 986940. Stack Space Delta: 5508 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 981432. Stack Space Delta: 5508 Allocated On Stack
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
Please unwind my stack
Stack space left: 976816. Stack Space Delta: 4616 Allocated On Stack
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
<-- RecurseXTimes()
Please unwind my stack
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
Stack space left: 982328. Stack Space Delta: 5512 Freed from Stack
<-- RecurseXTimes()
Please unwind my stack
Stack space left: 987832. Stack Space Delta: 5504 Freed from Stack
<-- RecurseXTimes()
Please unwind my stack
Stack space left: 993344. Stack Space Delta: 5512 Freed from Stack
<-- RecurseXTimes()
Please unwind my stack
Stack space left: 998848. Stack Space Delta: 5504 Freed from Stack
<-- RecurseXTimes()
Please unwind my stack
Stack space left: 1004360. Stack Space Delta: 5512 Freed from Stack
<-- RecurseXTimes()
Please unwind my stack
Stack space left: 1009864. Stack Space Delta: 5504 Freed from Stack
<-- RecurseXTimes()
Please unwind my stack
Stack space left: 1015376. Stack Space Delta: 5512 Freed from Stack
<-- RecurseXTimes()
Please unwind my stack
Stack space left: 1020880. Stack Space Delta: 5504 Freed from Stack
<-- RecurseXTimes()
Please unwind my stack
Stack space left: 1026392. Stack Space Delta: 5512 Freed from Stack
<-- RecurseXTimes()
Please unwind my stack
Stack space left: 1031896. Stack Space Delta: 5504 Freed from Stack
<-- RecurseXTimes()
System.Exception: Please unwind my stack
这是x64中完全相同代码的输出，堆栈空间随着下降而增加，但在展开期间继续减少：
Is64BitProcess = True
--> RecurseXTimes()
Stack space left: 1034256. Stack Space Delta: 5696 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 1028704. Stack Space Delta: 5552 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 1023152. Stack Space Delta: 5552 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 1017600. Stack Space Delta: 5552 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 1012048. Stack Space Delta: 5552 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 1006496. Stack Space Delta: 5552 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 1000944. Stack Space Delta: 5552 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 995392. Stack Space Delta: 5552 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 989840. Stack Space Delta: 5552 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 984288. Stack Space Delta: 5552 Allocated On Stack
Adding 5408 bytes to stack.
--> RecurseXTimes()
Stack space left: 978736. Stack Space Delta: 5552 Allocated On Stack
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
Please unwind my stack
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
Stack space left: 957392. Stack Space Delta: 21344 Allocated On Stack
<-- RecurseXTimes()
Please unwind my stack
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
Stack space left: 948880. Stack Space Delta: 8512 Allocated On Stack
<-- RecurseXTimes()
Please unwind my stack
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
Stack space left: 940368. Stack Space Delta: 8512 Allocated On Stack
<-- RecurseXTimes()
Please unwind my stack
Stack space left: 931856. Stack Space Delta: 8512 Allocated On Stack
<-- RecurseXTimes()
Please unwind my stack
Stack space left: 923344. Stack Space Delta: 8512 Allocated On Stack
<-- RecurseXTimes()
Please unwind my stack
Stack space left: 914832. Stack Space Delta: 8512 Allocated On Stack
<-- RecurseXTimes()
Please unwind my stack
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
Stack space left: 906320. Stack Space Delta: 8512 Allocated On Stack
<-- RecurseXTimes()
Please unwind my stack
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
Stack space left: 897808. Stack Space Delta: 8512 Allocated On Stack
<-- RecurseXTimes()
Please unwind my stack
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
Stack space left: 889296. Stack Space Delta: 8512 Allocated On Stack
<-- RecurseXTimes()
Please unwind my stack
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
Stack space left: 880784. Stack Space Delta: 8512 Allocated On Stack
<-- RecurseXTimes()
Please unwind my stack
A first chance exception of type 'System.Exception' occurred in ConsoleApplication16.exe
Stack space left: 872272. Stack Space Delta: 8512 Allocated On Stack
<-- RecurseXTimes()
System.Exception: Please unwind my stack
奇怪的是，如果我删除“Catch”然后在64位下它保持堆栈使用相同 - 但我不能在产品中执行此操作，因为我需要记录捕获。
答案 0 :(得分：1)
当您重新抛出异常时，似乎正在分配额外的内存块。因此，您仍然可以在生产代码中捕获它。
广泛的研究（谷歌确实如此）表明x64 stack unwind metadata可能是x64模式中额外分配的杯子。
我在示例代码中更改了RecurseXTimes中的异常catch，以便它：
并在接下来的最后Deserialze并抛出它。现在，堆栈展开跟踪在32位和64位模式之间看起来非常相似。
好的，所以你失去了异常网站的可见性，但它的递归仍然是至少，所以至少函数名是正确的..你可能需要理清你如何分配足够的内存来序列化它！
[编辑] 这是我做的调整：
catch (Exception e)
{
//Do some logging. NOTE taking this "catch" out "fixes" the problem, but I can't do this in prod.
System.Diagnostics.Debug.WriteLine(e.Message);
caughtException = new MemoryStream();
BinaryFormatter exceptionFormatter = new BinaryFormatter(); // Exception raised on this line
exceptionFormatter.Serialize(caughtException, e);
caughtException.Seek(0, SeekOrigin.Begin);
}
finally
{
ReportStackSpaceUsage();
System.Diagnostics.Debug.WriteLine("<-- RecurseXTimes()");
if (caughtException != null)
{
BinaryFormatter exceptionFormatter = new BinaryFormatter();
Exception e = (Exception)exceptionFormatter.Deserialize(caughtException);
throw e;
}
}
希望在您的真实应用程序中有足够的空间来执行此操作，而不会出现辅助OutOfMemoryException。
答案 1 :(得分：-2)
使用大量内存的递归，可以通过使用Stack对象在堆中执行。您可以自己增加/减少它，并获得更大的内存空间。