[commit: ghc] master: base: Fix fdReady() potentially running forever for Windows Char devices. (826c3b1)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/826c3b11780abcb74e5aba987e16369d69ac79a5/ghc

>---------------------------------------------------------------

commit 826c3b11780abcb74e5aba987e16369d69ac79a5
Author: Niklas Hambüchen <mail at nh2.me>
Date:   Tue Sep 19 15:10:31 2017 -0400

    base: Fix fdReady() potentially running forever for Windows Char devices.
    
    Reviewers: bgamari, austin, hvr
    
    Reviewed By: bgamari
    
    Subscribers: rwbarton, thomie
    
    Differential Revision: https://phabricator.haskell.org/D3955


>---------------------------------------------------------------

826c3b11780abcb74e5aba987e16369d69ac79a5
 libraries/base/cbits/inputReady.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/libraries/base/cbits/inputReady.c b/libraries/base/cbits/inputReady.c
index 14f1c54..ab2a1c2 100644
--- a/libraries/base/cbits/inputReady.c
+++ b/libraries/base/cbits/inputReady.c
@@ -102,6 +102,8 @@ fdReady(int fd, int write, int msecs, int isSock)
         HANDLE hFile = (HANDLE)_get_osfhandle(fd);
         DWORD avail;
 
+        Time remaining = MSToTime(msecs);
+
         switch (GetFileType(hFile)) {
 
             case FILE_TYPE_CHAR:
@@ -119,7 +121,11 @@ fdReady(int fd, int write, int msecs, int isSock)
 
                     while (1) // keep trying until we find a real key event
                     {
-                        rc = WaitForSingleObject( hFile, msecs );
+                        // WaitForSingleObject takes an unsigned number,
+                        // `remaining` can be negative. Wait 0 if so.
+                        DWORD wait_ms = (DWORD) max(0, TimeToMS(remaining));
+
+                        rc = WaitForSingleObject( hFile, wait_ms );
                         switch (rc) {
                             case WAIT_TIMEOUT: return 0;
                             case WAIT_OBJECT_0: break;
@@ -167,6 +173,9 @@ fdReady(int fd, int write, int msecs, int isSock)
                                 }
                             }
                         }
+
+                        Time now = getProcessElapsedTime();
+                        remaining = endTime - now;
                     }
                 }