From: <JC...@se...> - 2006-10-02 10:03:32
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Hi. I'm using Dev-C++ 4.9.9.2 with MinGW (gcc version 3.4.2). I'm writing an application for accessing Oracle database through ODBC. For the present I'm just learning methods to access database through ODBC API, but it's no important. Here is source code of sample application which uses ODBC (It's copied from Microsoft help): #include <windows.h> #include <sql.h> #include <sqlext.h> #include <stdlib.h> #include <mbstring.h> #define MAX_DATA 100 #define MYSQLSUCCESS(rc) ((rc==SQL_SUCCESS)||(rc==SQL_SUCCESS_WITH_ INFO)) class direxec { RETCODE rc; // ODBC return code HENV henv; // Environment HDBC hdbc; // Connection handle HSTMT hstmt; // Statement handle unsigned char szData[MAX_DATA]; // Returned data storage SDWORD cbData; // Output length of data unsigned char chr_ds_name[SQL_MAX_DSN_LENGTH]; // Data source name public: direxec(); // Constructor void sqlconn(); // Allocate env, stat, and conn void sqlexec(unsigned char *); // Execute SQL statement void sqldisconn(); // Free pointers to env, stat, conn, // and disconnect void error_out(); // Displays errors }; int WINAPI WinMain (HANDLE hInstance, HANDLE hPrevInstance, LPSTR lpszCmdLine, int nCmdShow) { // Declare an instance of the direxec object. direxec x; // Allocate handles, and connect. x.sqlconn(); // Execute SQL command "SELECT first name, last_name FROM employee". x.sqlexec((UCHAR FAR *)"SELECT first name, last_name FROM employee"); // Free handles, and disconnect. x.sqldisconn(); // Return success code; example executed successfully. return (TRUE); } // Constructor initializes the string chr_ds_name with the // data source name. direxec::direxec() { _mbscpy(chr_ds_name,(const unsigned char *)"Northwind"); } // Allocate environment handle, allocate connection handle, // connect to data source, and allocate statement handle. void direxec::sqlconn(void) { SQLAllocEnv(&henv); SQLAllocConnect(henv,&hdbc); rc=SQLConnect(hdbc,chr_ds_name,SQL_NTS,NULL,0,NULL,0); // Deallocate handles, display error message, and exit. if (!MYSQLSUCCESS(rc)) { SQLFreeEnv(henv); SQLFreeConnect(hdbc); error_out(); exit(-1); } rc=SQLAllocStmt(hdbc,&hstmt); } // Execute SQL command with SQLExecDirect() ODBC API. void direxec::sqlexec(unsigned char * cmdstr) { rc=SQLExecDirect(hstmt,cmdstr,SQL_NTS); if (!MYSQLSUCCESS(rc)) //Error { error_out(); // Deallocate handles and disconnect. SQLFreeStmt(hstmt,SQL_DROP); SQLDisconnect(hdbc); SQLFreeConnect(hdbc); SQLFreeEnv(henv); exit(-1); } else { for (rc=SQLFetch(hstmt); rc == SQL_SUCCESS; rc=SQLFetch(hstmt)) { SQLGetData(hstmt,1,SQL_C_CHAR,szData,sizeof(szData),& cbData); // In this example, the data is returned in a messagebox // for simplicity. However, normally the SQLBindCol() ODBC API // could be called to bind individual rows of data and assign // for a rowset. MessageBox(NULL,(const char *)szData,"ODBC",MB_OK); } } } // Free the statement handle, disconnect, free the connection handle, and // free the environment handle. void direxec::sqldisconn(void) { SQLFreeStmt(hstmt,SQL_DROP); SQLDisconnect(hdbc); SQLFreeConnect(hdbc); SQLFreeEnv(henv); } // Display error message in a message box that has an OK button. void direxec::error_out(void) { unsigned char szSQLSTATE[10]; SDWORD nErr; unsigned char msg[SQL_MAX_MESSAGE_LENGTH+1]; SWORD cbmsg; while(SQLError(0,0,hstmt,szSQLSTATE,&nErr,msg,sizeof(msg),&cbmsg)= = SQL_SUCCESS) { wsprintf((char *)szData,"Error:\nSQLSTATE=%s, Native error=%ld, msg='%s'",szSQLSTATE,nErr,msg); MessageBox(NULL,(const char *)szData,"ODBC Error",MB_OK); } } When I try to build this project (It's "Windows Application Project", defined in Dev-C++) with , I recive this: Compiler: Default compiler Building Makefile: "D:\Documents\to0745\Workspace\Makefile.win" Executing make clean rm -f main.o Project5.exe g++.exe -c main.cpp -o main.o -I"C:/Dev-Cpp/lib/gcc/mingw32/3.4.2/ include" -I"C:/Dev-Cpp/include/c++/3.4.2/backward" -I"C:/Dev-Cpp/ include/c++/3.4.2/mingw32" -I"C:/Dev-Cpp/include/c++/3.4.2" -I"C:/ Dev-Cpp/include" g++.exe main.o -o "Project5.exe" -L"C:/Dev-Cpp/lib" -mwindows odbc 32.lib C:/Dev-Cpp/lib/libmingw32.a(main.o)(.text+0x106):main.c: undefined reference to `WinMain@16' collect2: ld returned 1 exit status make.exe: *** [Project5.exe] Error 1 Execution terminated I searched Internet through the Google, but every issue concerning on "undefined reference to WinMain@16", was just a mistake in confusing main and WinMain. Here I'm adding Makefile: # Project: Project5 # Makefile created by Dev-C++ 4.9.9.2 CPP = g++.exe CC = gcc.exe WINDRES = windres.exe RES = OBJ = main.o $(RES) LINKOBJ = main.o $(RES) LIBS = -L"C:/Dev-Cpp/lib" -mwindows odbc32.lib INCS = -I"C:/Dev-Cpp/include" CXXINCS = -I"C:/Dev-Cpp/lib/gcc/mingw32/3.4.2/include" -I"C:/Dev-Cpp /include/c++/3.4.2/backward" -I"C:/Dev-Cpp/include/c++/3.4.2/mingw 32" -I"C:/Dev-Cpp/include/c++/3.4.2" -I"C:/Dev-Cpp/include" BIN = Project5.exe CXXFLAGS = $(CXXINCS) CFLAGS = $(INCS) RM = rm -f .PHONY: all all-before all-after clean clean-custom all: all-before Project5.exe all-after clean: clean-custom ${RM} $(OBJ) $(BIN) $(BIN): $(OBJ) $(CPP) $(LINKOBJ) -o "Project5.exe" $(LIBS) main.o: main.cpp $(CPP) -c main.cpp -o main.o $(CXXFLAGS) Thanks you very much for your advices... jcd |