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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