PRB: _lseek() Fails on Different Offset Values |
Q135326
The information in this article applies to: - The C Run-time (CRT) included with: - Microsoft Visual C++ for Windows, versions 1.0, 1.5, 1.51, 1.52 --------------------------------------------------------------------------- SYMPTOMS ======== The Run-Time function _lseek() fails on different offset values (number of bytes from origin). For example, in the following sample code, _lseek() fails if it seeks to the offset positions 0x1ffff, 0x2ffff, 0x3ffff and so on in a file. CAUSE ===== This behavior occurs when you fail to include the required header file IO.H. This header file contains the prototype for the _lseek() function. RESOLUTION ========== Include the header file. STATUS ====== This behavior is by design. MORE INFORMATION ================ If the code is compiled with warning level 3 or higher, the compiler will indicate that the function is not defined. It is a good idea to compile all code with a high warning level to prevent problems like this from happening. Sample Code to Reproduce Behavior --------------------------------- /* Compile options needed: None */ #include #include #include #include #include // #include // Uncomment this line to fix the problem void main() { int File; long temp; if ((File = _open("test.dat", O_RDWR | O_BINARY, S_IWRITE)) == -1 ){ printf("File open error \n"); exit(1); } temp = 0x0001fffeL; // This read works if (_lseek(File, temp, SEEK_SET) == -1L) printf("Error reading from position: %lx\n", temp); else printf("Read OK from position: %lx\n",temp); temp = 0x0001ffffL; // This read fails if (_lseek(File, temp, SEEK_SET) == -1L) printf("Error reading from position: %lx\n", temp); else printf("Read OK from position: %lx\n",temp); _close(File); } Additional query words: 8.00 8.00c lseek
Keywords : kb16bitonly kbLangC kbVC
Issue type : kbprb
Technology : kbVCsearch kbAudDeveloper kbCRT
Last Reviewed: May 5, 2001 |
