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diff --git a/winsup/doc/how-api.texinfo b/winsup/doc/how-api.texinfo deleted file mode 100644 index 6272582ae..000000000 --- a/winsup/doc/how-api.texinfo +++ /dev/null @@ -1,275 +0,0 @@ -@section Cygwin API Questions - -@subsection How does everything work? - -There's a C library which provides a Unix-style API. The -applications are linked with it and voila - they run on Windows. - -The aim is to add all the goop necessary to make your apps run on -Windows into the C library. Then your apps should run on Unix and -Windows with no changes at the source level. - -The C library is in a DLL, which makes basic applications quite small. -And it allows relatively easy upgrades to the Win32/Unix translation -layer, providing that dll changes stay backward-compatible. - -For a good overview of Cygwin, you may want to read the paper on Cygwin -published by the Usenix Association in conjunction with the 2d Usenix NT -Symposium in August 1998. It is available in html format on the project -WWW site. - -@subsection Are development snapshots for the Cygwin library available? - -Yes. They're made whenever anything interesting happens inside the -Cygwin library (usually roughly on a nightly basis, depending on how much -is going on). They are only intended for those people who wish to -contribute code to the project. If you aren't going to be happy -debugging problems in a buggy snapshot, avoid these and wait for a real -release. The snapshots are available from -http://cygwin.com/snapshots/ - - -@subsection How is the DOS/Unix CR/LF thing handled? - -@strong{(Please note: This section has not yet been updated for the latest -net release.)} - -Let's start with some background. - -In UNIX, a file is a file and what the file contains is whatever the -program/programmer/user told it to put into it. In Windows, a file is -also a file and what the file contains depends not only on the -program/programmer/user but also the file processing mode. - -When processing in text mode, certain values of data are treated -specially. A \n (new line) written to the file will prepend a \r -(carriage return) so that if you `printf("Hello\n") you in fact get -"Hello\r\n". Upon reading this combination, the \r is removed and the -number of bytes returned by the read is 1 less than was actually read. -This tends to confuse programs dependant on ftell() and fseek(). A -Ctrl-Z encountered while reading a file sets the End Of File flags even -though it truly isn't the end of file. - -One of Cygwin's goals is to make it possible to easily mix Cygwin-ported -Unix programs with generic Windows programs. As a result, Cygwin opens -files in text mode as is normal under Windows. In the accompanying -tools, tools that deal with binaries (e.g. objdump) operate in unix -binary mode and tools that deal with text files (e.g. bash) operate in -text mode. - -Some people push the notion of globally setting the default processing -mode to binary via mount point options or by setting the CYGWIN32 -environment variable. But that creates a different problem. In -binary mode, the program receives all of the data in the file, including -a \r. Since the programs will no longer deal with these properly for -you, you would have to remove the \r from the relevant text files, -especially scripts and startup resource files. This is a porter "cop -out", forcing the user to deal with the \r for the porter. - -It is rather easy for the porter to fix the source code by supplying the -appropriate file processing mode switches to the open/fopen functions. -Treat all text files as text and treat all binary files as binary. -To be specific, you can select binary mode by adding @code{O_BINARY} to -the second argument of an @code{open} call, or @code{"b"} to second -argument of an @code{fopen} call. You can also call @code{setmode (fd, -O_BINARY)}. - -Note that because the open/fopen switches are defined by ANSI, they -exist under most flavors of Unix; open/fopen will just ignore the switch -since they have no meaning to UNIX. - -Also note that @code{lseek} only works in binary mode. - -Explanation adapted from mailing list email by Earnie Boyd -<earnie_boyd@@yahoo.com>. - -@subsection Is the Cygwin library multi-thread-safe? - -Multi-thread-safe support is turned on by default in 1.1.x releases -(i.e., in the latest net release). That does not mean that it is bug -free! - -There is also limited support for 'POSIX threads', see the file -@code{cygwin.din} for the list of POSIX thread functions provided. - -@subsection Why is some functionality only supported in Windows NT? - -Windows 9x: n. -32 bit extensions and a graphical shell for a 16 bit patch to an -8 bit operating system originally coded for a 4 bit microprocessor, -written by a 2 bit company that can't stand 1 bit of competition. - -But seriously, Windows 9x lacks most of the security-related calls and -has several other deficiencies with respect to its version of the Win32 -API. See the calls.texinfo document for more information as to what -is not supported in Win 9x. - -@subsection How is fork() implemented? - -Cygwin fork() essentially works like a non-copy on write version -of fork() (like old Unix versions used to do). Because of this it -can be a little slow. In most cases, you are better off using the -spawn family of calls if possible. - -Here's how it works: - -Parent initializes a space in the Cygwin process table for child. -Parent creates child suspended using Win32 CreateProcess call, giving -the same path it was invoked with itself. Parent calls setjmp to save -its own context and then sets a pointer to this in the Cygwin shared -memory area (shared among all Cygwin tasks). Parent fills in the childs -.data and .bss subsections by copying from its own address space into -the suspended child's address space. Parent then starts the child. -Parent waits on mutex for child to get to safe point. Child starts and -discovers if has been forked and then longjumps using the saved jump -buffer. Child sets mutex parent is waiting on and then blocks on -another mutex waiting for parent to fill in its stack and heap. Parent -notices child is in safe area, copies stack and heap from itself into -child, releases the mutex the child is waiting on and returns from the -fork call. Child wakes from blocking on mutex, recreates any mmapped -areas passed to it via shared area and then returns from fork itself. - -@subsection How does wildcarding (globbing) work? - -If the DLL thinks it was invoked from a DOS style prompt, it runs a -`globber' over the arguments provided on the command line. This means -that if you type @code{LS *.EXE} from DOS, it will do what you might -expect. - -Beware: globbing uses @code{malloc}. If your application defines -@code{malloc}, that will get used. This may do horrible things to you. - -@subsection How do symbolic links work? - -Cygwin generates link files with a magic header. When -you open a file or directory that is a link to somewhere else, it -opens the file or directory listed in the magic header. Because we -don't want to have to open every referenced file to check symlink -status, Cygwin marks symlinks with the system attribute. Files -without the system attribute are not checked. Because remote samba -filesystems do not enable the system attribute by default, symlinks do -not work on network drives unless you explicitly enable this -attribute. - -@subsection Why do some files, which are not executables have the 'x' type. - -When working out the unix-style attribute bits on a file, the library -has to fill out some information not provided by the WIN32 API. - -It guesses that files ending in .exe and .bat are executable, as are -ones which have a "#!" as their first characters. - -@subsection How secure is Cygwin in a multi-user environment? - -Cygwin is not secure in a multi-user environment. For -example if you have a long running daemon such as "inetd" -running as admin while ordinary users are logged in, or if -you have a user logged in remotely while another user is logged -into the console, one cygwin client can trick another into -running code for it. In this way one user may gain the -priveledge of another cygwin program running on the machine. -This is because cygwin has shared state that is accessible by -all processes. - -(Thanks to Tim Newsham (newsham@@lava.net) for this explanation). - -@subsection How do the net-related functions work? - -@strong{(Please note: This section has not yet been updated for the latest -net release.)} - -The network support in Cygwin is supposed to provide the Unix API, not -the Winsock API. - -There are differences between the semantics of functions with the same -name under the API. - -E.g., the select system call on Unix can wait on a standard file handles -and handles to sockets. The select call in winsock can only wait on -sockets. Because of this, cygwin.dll does a lot of nasty stuff behind -the scenes, trying to persuade various winsock/win32 functions to do what -a Unix select would do. - -If you are porting an application which already uses Winsock, then -using the net support in Cygwin is wrong. - -But you can still use native Winsock, and use Cygwin. The functions -which cygwin.dll exports are called 'cygwin_<name>'. There -are a load of defines which map the standard Unix names to the names -exported by the dll -- check out include/netdb.h: - -@example -..etc.. -void cygwin_setprotoent (int); -void cygwin_setservent (int); -void cygwin_setrpcent (int); -..etc.. -#ifndef __INSIDE_CYGWIN_NET__ -#define endprotoent cygwin_endprotoent -#define endservent cygwin_endservent -#define endrpcent cygwin_endrpcent -..etc.. -@end example - -The idea is that you'll get the Unix->Cygwin mapping if you include -the standard Unix header files. If you use this, you won't need to -link with libwinsock.a - all the net stuff is inside the dll. - -The mywinsock.h file is a standard winsock.h which has been hacked to -remove the bits which conflict with the standard Unix API, or are -defined in other headers. E.g., in mywinsock.h, the definition of -struct hostent is removed. This is because on a Unix box, it lives in -netdb. It isn't a good idea to use it in your applications. - -As of the b19 release, this information may be slightly out of date. - -@subsection I don't want Unix sockets, how do I use normal Win32 winsock? - -@strong{(Please note: This section has not yet been updated for the latest -net release.)} - -To use the vanilla Win32 winsock, you just need to #define Win32_Winsock -and #include "windows.h" at the top of your source file(s). You'll also -want to add -lwsock32 to the compiler's command line so you link against -libwsock32.a. - -@subsection What version numbers are associated with Cygwin? - -@strong{(Please note: This section has not yet been updated for the latest -net release.)} - -There is a cygwin.dll major version number that gets incremented -every time we make a new Cygwin release available. This -corresponds to the name of the release (e.g. beta 19's major -number is "19"). There is also a cygwin.dll minor version number. If -we release an update of the library for an existing release, the minor -number would be incremented. - -There are also Cygwin API major and minor numbers. The major number -tracks important non-backward-compatible interface changes to the API. -An executable linked with an earlier major number will not be compatible -with the latest DLL. The minor number tracks significant API additions -or changes that will not break older executables but may be required by -newly compiled ones. - -Then there is a shared memory region compatibity version number. It is -incremented when incompatible changes are made to the shared memory -region or to any named shared mutexes, semaphores, etc. - -Finally there is a mount point registry version number which keeps track -of non-backwards-compatible changes to the registry mount table layout. -This has been "B15.0" since the beta 15 release. - -@subsection Why isn't _timezone set correctly? - -@strong{(Please note: This section has not yet been updated for the latest -net release.)} - -Did you explicitly call tzset() before checking the value of _timezone? -If not, you must do so. - -@subsection Is there a mouse interface? - -There is no way to capture mouse events from Cygwin. There are -currently no plans to add support for this. - |