请教一个诡异的问题:

[askeying]

我用vb调用c DLL的函数，DLL的两个出口函数如下：
bool _stdcall cleanuparray(char InBuffer[],int MaxSize)
{
int i;
memset(InBuffer,0,MaxSize);
for(i = 0; i < MaxSize; i++)
InBuffer[i] = 'a';
return false;

}

bool _stdcall mytest(char InBuffer[],int MaxSize)
{
return false;
}
vb的声明：
Declare Function cleanuparray Lib "mydll.dll" (InBuffer As Byte, ByVal MaxSize As Long) As Boolean
Declare Function mytest Lib "mydll.dll" (InBuffer As Byte, ByVal MaxSize As Long) As Boolean

vb程序如下：
x = cleanuparray(ab(0), MaxSize)
If x Then
MsgBox "x is true"
Else
MsgBox "x is false"
End If
y = mytest(ab(0), MaxSize)
If y Then
MsgBox "y is true"
Else
MsgBox "y is false"
End If
很奇怪的问题就是，“x is false”“y is true”,从DLL函数可以看出，两个函数不管什么情况下都返回false的。
而改用这种表达方式：
x = cleanuparray(ab(0), MaxSize)
If x = True Then
MsgBox "x is true"
Else
MsgBox "x is false"
End If
y = mytest(ab(0), MaxSize)
If y = True Then
MsgBox "y is true"
Else
MsgBox "y is false"
End If
结果却正确了："x is false"，"y is false"
if x then
跟if x=true then两者有这么大的区别吗？！

更诡异的是
我把vb声明改为：
Declare Function cleanuparray Lib "mydll.dll" (InBuffer As Byte, ByVal MaxSize As Long) As Long
Declare Function mytest Lib "mydll.dll" (InBuffer As Byte, ByVal MaxSize As Long) As Long
的时候，
昨天晚上用if y then，if y=true then（包括x）判断都正确，
今天早上起来，同样的情况下，if y then 却判断失常了，y好像总是true（其实肯定返回false）。

我不明白，为什么if x then总能判断正确，而if y then却会失常？

高手指点，谢谢！！

[XunBaian]

VC中的bool或BOOL函数，在VB中声明，般都是用Long的，VB返回非零即VC的true或TRUE，零为false或FALSE，所以你应如下：
Declare Function cleanuparray Lib "mydll.dll" (InBuffer As Byte, ByVal MaxSize As Long) As Long
Declare Function mytest Lib "mydll.dll" (InBuffer As Byte, ByVal MaxSize As Long) As Long


x = cleanuparray(ab(0), MaxSize)
If x <> 0 Then
MsgBox "x is true"
Else
MsgBox "x is false"
End If
y = mytest(ab(0), MaxSize)
If y <> 0 Then
MsgBox "y is true"
Else
MsgBox "y is false"
End If

[XunBaian]

对于这种调试，你应如下使用：
x = cleanuparray(ab(0), MaxSize)
MsgBox "x is " & x

y = mytest(ab(0), MaxSize)
MsgBox "y is " & y

[XunBaian]

另外，VB中的True其实为-1，当你的VB返回TRUE或true时，其值不一定是-1，可能其它非0的数，你可以在VB的立即窗口试试：

?3=true 回车(这里的3可换成其它非-1的数测试)

得到False

[askeying]

照你的第一个方法，y还是很奇怪的是true..
照你的
x = cleanuparray(ab(0), MaxSize)
MsgBox "x is " & x

y = mytest(ab(0), MaxSize)
MsgBox "y is " & y
改动后，
总是y is true

难道是我dll的函数总是返回true了？！

但是我用If y = True Then的表达方式，
y是false的

怎么解释？

[askeying]

加我qq4170227，好吗？仔细跟你谈谈

[askeying]

明白了,谢谢.