Re: cvs commit: fptools/libraries/base/GHC ConsoleHandler.hsfptools/libraries/base/cbits consUtils.cfptools/libraries/base/include consUtils.hfptools/ghc/compiler/ghci InteractiveUI.hs

[Sigbjorn Finne]

Thanks, believe it is a bit better behaved now in
that usage mode.
--sigbjorn
----- Original Message ----- 
From: "Krasimir Angelov" <[EMAIL PROTECTED]>
To: "Sigbjorn Finne" <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
Sent: Thursday, May 12, 2005 03:40
Subject: Re: cvs commit: fptools/libraries/base/GHC 
ConsoleHandler.hsfptools/libraries/base/cbits 
consUtils.cfptools/libraries/base/include 
consUtils.hfptools/ghc/compiler/ghci InteractiveUI.hs


Hi Sigbjorn,
The workaround breaks another useful feature of GHC. You can't spawn
GHCi through runInteractiveProcess anymore. You should use
flushConsole only if the stdin is console handle.
Cheers,
 Krasimir
On 5/6/05, Sigbjorn Finne <[EMAIL PROTECTED]> wrote:
sof         2005/05/05 17:30:58 PDT
 Modified files:
   libraries/base/GHC   ConsoleHandler.hs
   libraries/base/cbits consUtils.c
   libraries/base/include consUtils.h
   ghc/compiler/ghci    InteractiveUI.hs
 Log:
 [mingw only]
 Work around bug in win32 Console API which showed up in the GHCi UI:
 if the user typed in characters prior to the appearance of the prompt,
 the first of these characters always came out as a 'g'. The GHCi UI does
 for good reasons one-character reads from 'stdin', which causes the
 underlying APIs to become confused. A simple repro case is the following
 piece of C code:
 /*----------------------*/
 #include <stdio.h>
 #include <windows.h>
 int main()
 {
     char ch1,ch2;
     HANDLE hStdIn = GetStdHandle(STD_INPUT_HANDLE);
     DWORD dw;
     /* Type in some characters before the prompt appears and be amused.. 
*/
     sleep(1000); printf("? ");
     ReadConsoleA(hStdIn,&ch1,1,&dw,NULL);
     ReadConsoleA(hStdIn,&ch2,1,&dw,NULL);
 /*  or, if you want to use libc:
     read(0,&ch1,1); read(0,&ch2,1); */

     printf("%c%c\n", ch1,ch2);
     return 0;
 }
 /*----------------------*/
 This happens across win32 OSes, and I can't see anything untoward as far
 as API usage goes (the GHC IO implementation uses read(), but that
 reduces to ReadConsoleA() calls.) People inside the Behemoth might want
 to have a closer look at this..
 Not much we can do about this except work around the problem by flushing
 the input buffer prior to reading from stdin. Not ideal, as type-ahead
 is a useful feature. Flushing is handled by 
GHC.ConsoleHandler.flushConsole

 Merge to STABLE.
 Revision  Changes    Path
 1.8       +13 -0     fptools/libraries/base/GHC/ConsoleHandler.hs
 1.5       +13 -0     fptools/libraries/base/cbits/consUtils.c
 1.2       +1 -0      fptools/libraries/base/include/consUtils.h
 1.203     +9 -0      fptools/ghc/compiler/ghci/InteractiveUI.hs
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