我正在使用Visual Studio 2005中的DLL和EXE项目。在DLL的代码中，有一个可扩展数组类的模板：
template <class Type>
class GArray
{
Type *p;
uint32 len;
uint32 alloc;
protected:
bool fixed;
public:
/// Constructor
GArray(int PreAlloc = 0)
{
p = 0;
len = 0;
fixed = false;
alloc = PreAlloc;
if (alloc)
{
int Bytes = sizeof(Type) * alloc;
p = (Type*) malloc(Bytes);
if (p)
{
memset(p, 0, Bytes);
}
else
{
alloc = 0;
}
}
}
/// Destructor
~GArray()
{
Length(0);
}
/// Returns the number of used entries
uint32 Length() const
{
return len;
}
/// Sets the length of available entries
bool Length(uint32 i)
{
if (i > 0)
{
if (i > len && fixed)
return false;
uint nalloc = alloc;
if (i < len)
{
// Shrinking
}
else
{
// Expanding
int b;
for (b = 4; (1 << b) < i; b++)
;
nalloc = 1 << b;
LgiAssert(nalloc >= i);
}
if (nalloc != alloc)
{
Type *np = (Type*)malloc(sizeof(Type) * nalloc);
if (!np)
{
return false;
}
if (p)
{
// copy across common elements
memcpy(np, p, min(len, i) * sizeof(Type));
free(p);
}
p = np;
alloc = nalloc;
}
if (i > len)
{
// zero new elements
memset(p + len, 0, sizeof(Type) * (i - len));
}
len = i;
}
else
{
if (p)
{
int Length = len;
for (uint i=0; i<Length; i++)
{
p[i].~Type();
}
free(p);
p = 0;
}
len = alloc = 0;
}
return true;
}
GArray<Type> &operator =(const GArray<Type> &a)
{
Length(a.Length());
if (p && a.p)
{
for (int i=0; i<len; i++)
{
p[i] = a.p[i];
}
}
return *this;
}
/// \brief Returns a reference a given entry.
///
/// If the entry is off the end of the array and "fixed" is false,
/// it will grow to make it valid.
Type &operator [](uint32 i)
{
static Type t;
if
(
i < 0
||
(fixed && i >= len)
)
{
ZeroObj(t);
return t;
}
#if 0
if (i > 15000000)
{
#if defined(_DEBUG) && defined(_MSC_VER)
LgiAssert(0);
#endif
ZeroObj(t);
return t;
}
#endif
if (i >= alloc)
{
// increase array length
uint nalloc = max(alloc, GARRAY_MIN_SIZE);
while (nalloc <= i)
{
nalloc <<= 1;
}
// alloc new array
Type *np = (Type*) malloc(sizeof(Type) * nalloc);
if (np)
{
// clear new cells
memset(np + len, 0, (nalloc - len) * sizeof(Type));
if (p)
{
// copy across old cells
memcpy(np, p, len * sizeof(Type));
// clear old array
free(p);
}
// new values
p = np;
alloc = nalloc;
}
else
{
static Type *t = 0;
return *t;
}
}
// adjust length of the the array
if (i + 1 > len)
{
len = i + 1;
}
return p[i];
}
/// Delete all the entries as if they are pointers to objects
void DeleteObjects()
{
for (uint i=0; i<len; i++)
{
DeleteObj(p[i]);
}
Length(0);
}
/// Delete all the entries as if they are pointers to arrays
void DeleteArrays()
{
for (int i=0; i<len; i++)
{
DeleteArray(p[i]);
}
Length(0);
}
/// Find the index of entry 'n'
int IndexOf(Type n)
{
for (uint i=0; i<len; i++)
{
if (p[i] == n) return i;
}
return -1;
}
/// Returns true if the item 'n' is in the array
bool HasItem(Type n)
{
return IndexOf(n) >= 0;
}
/// Deletes an entry
bool DeleteAt
(
/// The index of the entry to delete
uint Index,
/// true if the order of the array matters, otherwise false.
bool Ordered = false
)
{
if (p && Index >= 0 && Index < len)
{
// Delete the object
p[Index].~Type();
// Move the memory up
if (Index < len - 1)
{
if (Ordered)
{
memmove(p + Index, p + Index + 1, (len - Index - 1) * sizeof(Type) );
}
else
{
p[Index] = p[len-1];
}
}
// Adjust length
len--;
return true;
}
return false;
}
/// Deletes the entry 'n'
bool Delete
(
/// The value of the entry to delete
Type n,
/// true if the order of the array matters, otherwise false.
bool Ordered = false
)
{
int i = IndexOf(n);
if (p && i >= 0)
{
return DeleteAt(i, Ordered);
}
return false;
}
/// Appends an element
void Add
(
/// Item to insert
const Type &n
)
{
(*this)[len] = n;
}
/// Appends multiple elements
void Add
(
/// Items to insert
Type *s,
/// Length of array
int count
)
{
if (!s || count < 1)
return;
int i = len;
Length(len + count);
Type *d = p + i;
while (count--)
{
*d++ = *s++;
}
}
/// Inserts an element into the array
bool AddAt
(
/// Item to insert before
int Index,
/// Item to insert
Type n
)
{
// Make room
if (Length(len + 1))
{
if (Index < len - 1)
{
// Shift elements after insert point up one
memmove(p + Index + 1, p + Index, (len - Index - 1) * sizeof(Type) );
}
else if (Index >= len)
{
// Add at the end, not after the end...
Index = len - 1;
}
// Insert item
p[Index] = n;
return true;
}
return false;
}
/// Sorts the array
void Sort(int (*Compare)(Type*, Type*))
{
typedef int (*qsort_compare)(const void *, const void *);
qsort(p, len, sizeof(Type), (qsort_compare)Compare);
}
/// \returns a reference to a new object on the end of the array
Type &New()
{
return (*this)[len];
}
/// Returns the memory held by the array and sets itself to empty
Type *Release()
{
Type *Ptr = p;
p = 0;
len = alloc = 0;
return Ptr;
}
};
我在几个地方的EXE中重用了这段代码。但是，当我在一个特定文件中使用它时，我开始收到重复的符号链接错误：
2>lgi8d.lib(Lgi8d.dll) : error LNK2005: "public: int __thiscall GArray<char *>::Length(void)" (?Length@?$GArray@PAD@@QAEHXZ) already defined in FrameStore.obj
2>D:\Home\matthew\network_camera\src\vod_test\Debug\vod_test.exe : fatal error LNK1169: one or more multiply defined symbols found
我在EXE中的其他文件中使用了相同的类而没有错误。例如在Camera.cpp我有：
void DeleteFromArray(GArray<char> &a, int Start, int Len)
{
assert(Len >= 0);
int64 StartTs = LgiCurrentTime();
int Del = min(Len, a.Length() - Start);
if (Del > 0)
{
int Remain = a.Length() - Start - Del;
if (Remain > 0)
{
memmove(&a[Start], &a[Start+Del], Remain);
MoveBytes += Remain;
a.Length(Start+Remain);
}
else a.Length(Start);
}
int64 End = LgiCurrentTime();
DeleteTime += End - StartTs;
}
编译并链接ok ...但在FrameStore.cpp中：
void Scan()
{
if (!Init)
{
Init = true;
GAutoString Path = FrameFile::GetPath();
GAutoPtr<GDirectory> Dir(FileDev->GetDir());
GArray<char*> k;
int64 Size = 0;
for (bool b = Dir->First(Path); b; b = Dir->Next())
{
if (!Dir->IsDir())
{
char *e = LgiGetExtension(Dir->GetName());
if (e && !stricmp(e, "mjv"))
{
char p[MAX_PATH];
Dir->Path(p, sizeof(p));
k.Add(NewStr(p));
Size += Dir->GetSize();
}
}
}
GAutoPtr<Prog> p(new Prog(Size));
for (int i=0; i<k.Length(); i++)
{
Files.Add(new FrameFile(k[i], p));
}
k.DeleteArrays();
}
}
在其中带有“k.Length（）”的行上导致链接错误...如果我注释掉它链接！然而，我在相同的代码中使用GArray类中的其他方法，它们不会导致问题。
为什么完全在标题中定义的模板类首先会出现此问题？
答案 0 :(得分：3)
问题：
Lgi.dll中定义了另一个导出GArray实例化的类。
#ifdef LGI_DLL
#define LgiClass __declspec(dllexport)
#else
#define LgiClass __declspec(dllimport)
#endif
class LgiClass GToken : public GArray<char*>
{
/// stuff...
};
解决方案：
在我的EXE中包含GToken标头，特别是使用GArray实现的FrameStore.cpp文件，然后编译将从DLL导入这些符号而不是重复它们。
如果编译器可以给我更多关于DLL定义符号的提示，那将是很好的。简单地说“某处有重复”并不是很有帮助。
答案 1 :(得分：0)
如果您使用的是Visual Studio 6，请确保设置了以下选项：
项目 - ＆GT;设置 - ＆GT; C / C ++ - ＆GT;代码生成 - ＆gt;使用运行时库===＆gt; Debug Multithreaded / Multithreaded
编辑： 在VS 2005中它基本相同。
项目 - ＆GT;属性 - ＆GT;配置属性 - ＆gt; C / C ++ - ＆gt;代码生成 - ＆gt;运行时库 - ＆gt;多线程/多线程调试
答案 2 :(得分：0)
作为旁注，你可能想要拆分你的声明和定义，所以它不是那么难看：
template <class Type>
class GArray
{
Type *p;
uint32 len;
uint32 alloc;
protected:
bool fixed;
public:
GArray(int PreAlloc = 0);
/// Destructor
~GArray() {Length(0);}
/// Returns the number of used entries
int Length() {return len;}
/// Sets the length of available entries
bool Length(uint32 i);
// etc...
};
template <class Type>
GArray<Type>::GArray(int PreAlloc = 0)
{
p = 0;
len = 0;
fixed = false;
alloc = PreAlloc;
if (alloc)
{
int Bytes = sizeof(Type) * alloc;
p = (Type*) malloc(Bytes);
if (p)
{
memset(p, 0, Bytes);
}
else
{
alloc = 0;
}
}
}
template <class Type>
bool GArray<Type>::Length(uint32 i);
{
if (i > 0)
{
if (i > len && fixed)
return false;
uint nalloc = alloc;
if (i < len)
{
// Shrinking
}
else
{
// Expanding
int b;
for (b = 4; (1 << b) < i; b++)
;
nalloc = 1 << b;
LgiAssert(nalloc >= i);
}
if (nalloc != alloc)
{
Type *np = (Type*)malloc(sizeof(Type) * nalloc);
if (!np)
{
return false;
}
if (p)
{
// copy across common elements
memcpy(np, p, min(len, i) * sizeof(Type));
free(p);
}
p = np;
alloc = nalloc;
}
if (i > len)
{
// zero new elements
memset(p + len, 0, sizeof(Type) * (i - len));
}
len = i;
}
else
{
if (p)
{
int Length = len;
for (uint i=0; i<Length; i++)
{
p[i].~Type();
}
free(p);
p = 0;
}
len = alloc = 0;
}
return true;
}
//你明白了
另外，operator=应该使用const GArray<Type>&表示右侧不会改变。
答案 3 :(得分：0)
2>lgi8d.lib(Lgi8d.dll) : error LNK2005: "public: int __thiscall GArray<char *>::Length(void)" (?Length@?$GArray@PAD@@QAEHXZ) already defined in FrameStore.obj
2>D:\Home\matthew\network_camera\src\vod_test\Debug\vod_test.exe : fatal error LNK1169: one or more multiply defined symbols found
lgi8d.lib和vod_test.exe是两个独立的二进制文件。问题可能在于.lib已经定义了.exe再次定义的符号。
答案 4 :(得分：0)
您可以尝试在DLL中的类中添加declspec（dllexport），在EXE中添加declspec（dllimport）。 E.g。
#if !defined(MYDLLEXPORT)
// We are users of, and *importing* the library routines...
#define MYLIB_SPEC __declspec(dllimport)
#else
// We are building and exporting the library routines...
#define MYLIB_SPEC __declspec(dllexport)
#endif
// ...
template<typename Type>
class MYLIB_SPEC GArray // ...
然后确保在构建DLL的项目中定义了MYDLLEXPORT，并且没有为EXE定义。
AFAIK，你通常不需要这个模板。
关于declspec的更多信息：http://msdn.microsoft.com/en-us/library/a90k134d(VS.80).aspx。
答案 5 :(得分：0)
为什么不使用std :: vector？