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我是mmap新手，仍然在學習它。根據我的理解，我已經創建了mmap類，它將用於映射內存中的文件。整個班級工作正常，但問題是當析構函數被調用時..問題是分段錯誤或無效指針錯誤是在主函數的末尾...我已經發布了我的類和主函數的代碼正在使用類...mmap錯誤：分段錯誤/無效指針錯誤
Map.h
class MapData
{
public :
MapData();
~MapData();
MapData(char []);
bool OPEN();
void fnClose();
long fnGetSize();
char * fnGetFileRef();
char * ReadNextData(int);
private :
char * ptrRecord;
char ptrFileNm[250+1];
int fd;
struct stat sbuf;
bool bSuccess;
long sTotalSize;
char acData[2000+1];
long lCurrRead;
};
MapData.cpp
MapData::MapData()
{
}
MapData::~MapData()
{
printf("Inside MADATA Destructor \n ");
}
MapData::MapData(char acInput[])
{
strcpy(ptrFileNm,acInput);
sTotalSize=0;
lCurrRead=0;
bSuccess=false;
}
bool MapData::OPEN()
{
// if failed return false flg
if ((fd = open(ptrFileNm, O_RDONLY)) == -1) {
return bSuccess;
}
if (stat(ptrFileNm, &sbuf) == -1) {
return bSuccess;
}
// copy in local variable
sTotalSize = sbuf.st_size;
ptrRecord = (char *)mmap((caddr_t)0, sTotalSize, PROT_READ, MAP_SHARED, fd, 0) ;
if (ptrRecord == (char *)(caddr_t)(-1)) {
perror("Fail to Map Data ");
return bSuccess;
}
else
{
printf("Successfully Map Data***[%ld] \n",sTotalSize);
bSuccess=true;
}
return bSuccess;
}
char * MapData::fnGetFileRef()
{
return ptrRecord;
}
char * MapData::ReadNextData(int iX)
{
if((lCurrRead+iX)<sTotalSize)
{
memset(acData,0x00,sizeof(acData));
strncpy(acData,ptrRecord+lCurrRead,iX);
acData[iX+1]='\0';
lCurrRead+=iX;
}else{
strcpy(acData,"ZZZ");
}
return acData;
}
long MapData::fnGetSize()
{
return sTotalSize;
}
void MapData::fnClose()
{
// Don't forget to free the mmapped memory
if(munmap(ptrRecord, sTotalSize) == -1)
{
close(fd);
perror("Error un-mmapping the file");
exit(EXIT_FAILURE);
}
// Un-mmaping doesn't close the file, so we still need to do that.
close(fd);
printf("CLOSED SUCCESSFULLY \n ");
}
Main.cpp的
int main()
{
char acFileNm[500+1];
MEMSET(acFileNm); // clean the variable
// file name to be read
strcpy(acFileNm,"ABDFILE.txt");
long lProcCnt=0; // no of byte read by program
char acLine[MAX_LINE_LENGTH+1]; // hold current read line
bool bFlag=true; // main flag
DEBUG_PRINT("File to be processed:%s \n",acFileNm);
// create object of mmap
MapData * pt1 = NULL;
pt1 = new MapData(acFileNm);
if(!pt1)
{
cout<<"Error creating object so quit ..."<<endl;
return 0 ;
}
auto_ptr<MapData> ptrMap(pt1); // pass ownership to auto deletor to delete memory
DEBUG_PRINT("STEP1:%s \n","OBJECT CREATION FOR FILE MAPPED IN MEMORY");
// try to open the file
if(ptrMap->OPEN())
{
// on success..get pointer to first char of file
char * ptrData = ptrMap->fnGetFileRef();
long lCompSize=ptrMap->fnGetSize(); // total no of bytes = fiexed line size * no of row + (no of row * EOL)
short int iEOL=0;
// logic to identify file generated on ewhich OS
if((*(ptrData+MAX_LINE_LENGTH) == '\r') && (*(ptrData+MAX_LINE_LENGTH+1) == '\n'))
{
// DOS format CRLF
iEOL = 2;
}else if(*(ptrData+MAX_LINE_LENGTH) == '\n'){
// Unix format LF
iEOL = 1;
}
DEBUG_PRINT("STEP2: SIZEOFFILE%ld FILESYSTEM FORMAT:%d \n",lCompSize,iEOL);
// here read till it reaches maximum limit of file
while(lProcCnt<lCompSize)
{
//DEBUG_PRINT("PROC COUNTER[%ld] MAX_COUNTER[%ld] \n",lProcCnt,lCompSize);
lProcCnt+=MAX_LINE_LENGTH+iEOL; // increement no of bytes read at initial
MEMSET(acLine);
strncpy(acLine,ptrData+lProcCnt,MAX_LINE_LENGTH); // read line
acLine[MAX_LINE_LENGTH+1]='\0';
// process the line :function is called here to process the line
}
}else{
DEBUG_PRINT("MAP DATA FAILED OF FILE[%s] \n",acFileNm);
bFlag=false;
}
// at the end check if all the controls are matched
if(bFlag)
DEBUG_PRINT("END OF FILE PROCESSING SUCCESS \n");
else
DEBUG_PRINT("END OF FILE PROCESSING FAILED \n");
// close the memory map
ptrMap->fnClose();
MapData * ptr5 = ptrMap.release(); // release the ownership
delete ptr5; **// segmentation fault comes here ...**
}
請建議我在哪裏，我錯了，因爲GDB也沒有幫助...詳細的解釋將是對我好明白......
Stacktrace generated by gdb:
*** glibc detected *** DemoMap: free(): invalid pointer: 0x0804c000 ***
======= Backtrace: =========
/lib/libc.so.6[0x9bbc81]
/lib/libc.so.6[0x9be562]
/usr/lib/libstdc++.so.6(_ZdlPv+0x22)[0x544552]
DemoMap[0x80491e6]
/lib/libc.so.6(__libc_start_main+0xe6)[0x961d36]
DemoMap[0x8048d91]
======= Memory map: ========
00110000-00111000 r-xp 00000000 00:00 0 [vdso]
0044c000-00469000 r-xp 00000000 08:03 1237 /lib/libgcc_s-4.4.7-20120601.so.1
00469000-0046a000 rw-p 0001d000 08:03 1237 /lib/libgcc_s-4.4.7-20120601.so.1
00495000-00576000 r-xp 00000000 08:02 132841 /usr/lib/libstdc++.so.6.0.13
00576000-0057a000 r--p 000e0000 08:02 132841 /usr/lib/libstdc++.so.6.0.13
0057a000-0057c000 rw-p 000e4000 08:02 132841 /usr/lib/libstdc++.so.6.0.13
0057c000-00582000 rw-p 00000000 00:00 0
00929000-00947000 r-xp 00000000 08:03 1065 /lib/ld-2.12.so
00947000-00948000 r--p 0001d000 08:03 1065 /lib/ld-2.12.so
00948000-00949000 rw-p 0001e000 08:03 1065 /lib/ld-2.12.so
0094b000-00adb000 r-xp 00000000 08:03 1067 /lib/libc-2.12.so
00adb000-00adc000 ---p 00190000 08:03 1067 /lib/libc-2.12.so
00adc000-00ade000 r--p 00190000 08:03 1067 /lib/libc-2.12.so
00ade000-00adf000 rw-p 00192000 08:03 1067 /lib/libc-2.12.so
00adf000-00ae2000 rw-p 00000000 00:00 0
00b29000-00b51000 r-xp 00000000 08:03 1211 /lib/libm-2.12.so
00b51000-00b52000 r--p 00027000 08:03 1211 /lib/libm-2.12.so
00b52000-00b53000 rw-p 00028000 08:03 1211 /lib/libm-2.12.so
08048000-0804b000 r-xp 00000000 08:08 2883976 DemoMap
0804b000-0804c000 rw-p 00002000 08:08 2883976 DemoMap
0804c000-0806d000 rw-p 00000000 00:00 0 [heap]
b7e00000-b7e21000 rw-p 00000000 00:00 0
b7e21000-b7f00000 ---p 00000000 00:00 0
b7f9b000-b7fe5000 r--s 00000000 08:08 4326707 ABCDEF.TXT
b7fe5000-b7fe8000 rw-p 00000000 00:00 0
b7ffd000-b8000000 rw-p 00000000 00:00 0
bffeb000-c0000000 rw-p 00000000 00:00 0 [stack]
編輯......此類我要去通過映射內存中的文件進行快速訪問用於文件處理... – macmore
請考慮增加調試輸出（如'printf's）熬下來到代碼中更具體的部分，這可能有助於確定問題。如果所有在那裏完成的都是'printf（「Inside MADATA Destructor \ n」）;那麼析構函數應該是什麼問題？ –
我試着用各種可能的方式使用gdb進行調試...程序得到執行正常，但在刪除調用Mmap指針析構函數被調用和程序停止..我在這裏張貼由gdb生成的堆棧跟蹤....... – macmore