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Win32: reliably detect console pipe handles

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As of "Win32: Thread-safe windows console output", child processes may
print to the console even if stdout has been redirected to a file. E.g.:

 git config tar.cat.command "cat"
 git archive -o test.cat HEAD

Detecting whether stdout / stderr point to our console pipe is currently
based on the assumption that OS HANDLE values are never reused. This is
apparently not true if stdout / stderr is replaced via dup2() (as in
builtin/archive.c:17).

Instead of comparing handle values, check if the file descriptor isatty()
backed by a pipe OS handle. This is only possible by swapping the handles
in MSVCRT's internal data structures, as we do in winansi_init().

Reported-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Karsten Blees 2014-06-14 00:09:06 +02:00 committed by Junio C Hamano
parent fcd428f4a9
commit 51822653f5
1 changed files with 7 additions and 18 deletions
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25
compat/winansi.c
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@ -20,7 +20,6 @@ static WORD attr;
static int negative;
static int non_ascii_used = 0;
static HANDLE hthread, hread, hwrite;
static HANDLE hwrite1 = INVALID_HANDLE_VALUE, hwrite2 = INVALID_HANDLE_VALUE;
static HANDLE hconsole1, hconsole2;
#ifdef __MINGW32__
@ -435,10 +434,6 @@ static void winansi_exit(void)
WaitForSingleObject(hthread, INFINITE);
/* cleanup handles... */
if (hwrite1 != INVALID_HANDLE_VALUE)
CloseHandle(hwrite1);
if (hwrite2 != INVALID_HANDLE_VALUE)
CloseHandle(hwrite2);
CloseHandle(hwrite);
CloseHandle(hthread);
}
@ -565,14 +560,9 @@ void winansi_init(void)
/* redirect stdout / stderr to the pipe */
if (con1)
hconsole1 = swap_osfhnd(1, hwrite1 = duplicate_handle(hwrite));
hconsole1 = swap_osfhnd(1, duplicate_handle(hwrite));
if (con2)
hconsole2 = swap_osfhnd(2, hwrite2 = duplicate_handle(hwrite));
}
static int is_same_handle(HANDLE hnd, int fd)
{
return hnd != INVALID_HANDLE_VALUE && hnd == (HANDLE) _get_osfhandle(fd);
hconsole2 = swap_osfhnd(2, duplicate_handle(hwrite));
}
/*
@ -581,10 +571,9 @@ static int is_same_handle(HANDLE hnd, int fd)
*/
HANDLE winansi_get_osfhandle(int fd)
{
if (fd == 1 && is_same_handle(hwrite1, 1))
return hconsole1;
else if (fd == 2 && is_same_handle(hwrite2, 2))
return hconsole2;
else
return (HANDLE) _get_osfhandle(fd);
HANDLE hnd = (HANDLE) _get_osfhandle(fd);
if ((fd == 1 || fd == 2) && isatty(fd)
&& GetFileType(hnd) == FILE_TYPE_PIPE)
return (fd == 1) ? hconsole1 : hconsole2;
return hnd;
}