git-commit-vandalism/compat
Johannes Sixt 75301f9015 Windows: avoid the "dup dance" when spawning a child process
When stdin, stdout, or stderr must be redirected for a child process that
on Windows is spawned using one of the spawn() functions of Microsoft's
C runtime, then there is no choice other than to

1. make a backup copy of fd 0,1,2 with dup
2. dup2 the redirection source fd into 0,1,2
3. spawn
4. dup2 the backup back into 0,1,2
5. close the backup copy and the redirection source

We used this idiom as well -- but we are not using the spawn() functions
anymore!

Instead, we have our own implementation. We had hardcoded that stdin,
stdout, and stderr of the child process were inherited from the parent's
fds 0, 1, and 2. But we can actually specify any fd.

With this patch, the fds to inherit are passed from start_command()'s
WIN32 section to our spawn implementation. This way, we can avoid the
backup copies of the fds.

The backup copies were a bug waiting to surface: The OS handles underlying
the dup()ed fds were inherited by the child process (but were not
associated with a file descriptor in the child). Consequently, the file or
pipe represented by the OS handle remained open even after the backup copy
was closed in the parent process until the child exited.

Since our implementation of pipe() creates non-inheritable OS handles, we
still dup() file descriptors in start_command() because dup() happens to
create inheritable duplicates. (A nice side effect is that the fd cleanup
in start_command is the same for Windows and Unix and remains unchanged.)

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2010-01-16 16:43:53 -08:00
..
fnmatch Fix more typos/spelling in comments 2009-04-22 19:03:39 -07:00
nedmalloc Fix typo in nedmalloc warning fix 2009-06-11 14:18:52 -07:00
regex Change regerror() declaration from K&R style to ANSI C (C89) 2009-09-18 20:00:42 -07:00
vcbuild Merge branch 'ef/msys-imap' 2009-11-17 22:03:00 -08:00
basename.c compat: add a basename() compatibility function 2009-05-31 17:57:59 -07:00
bswap.h Explicitly truncate bswap operand to uint32_t 2009-11-25 00:16:38 -08:00
cygwin.c Fix more typos/spelling in comments 2009-04-22 19:03:39 -07:00
cygwin.h cygwin: Use native Win32 API for stat 2008-09-30 14:30:06 -07:00
fopen.c compat/fopen.c: avoid clobbering the system defined fopen macro 2008-05-08 17:43:01 -07:00
hstrerror.c Add a local implementation of hstrerror for the system which do not have it 2007-06-15 22:48:34 -07:00
inet_ntop.c Remove a couple of duplicated include 2007-11-05 20:50:38 -08:00
inet_pton.c Remove a couple of duplicated include 2007-11-05 20:50:38 -08:00
memmem.c optimize compat/ memmem() 2009-03-02 18:28:06 -08:00
mingw.c Windows: avoid the "dup dance" when spawning a child process 2010-01-16 16:43:53 -08:00
mingw.h Windows: avoid the "dup dance" when spawning a child process 2010-01-16 16:43:53 -08:00
mkdtemp.c Define compat version of mkdtemp for systems lacking it 2007-10-20 22:52:21 -04:00
mkstemps.c compat: add a mkstemps() compatibility function 2009-05-31 17:56:44 -07:00
mmap.c War on whitespace 2007-06-07 00:04:01 -07:00
msvc.c Add platform files for porting to MSVC 2009-09-18 20:00:42 -07:00
msvc.h Define strncasecmp and ftruncate for MSVC 2009-09-18 20:00:42 -07:00
pread.c Replacing the system call pread() with lseek()/xread()/lseek() sequence. 2007-01-09 16:40:40 -08:00
qsort.c compat: Add simplified merge sort implementation from glibc 2008-02-06 22:35:28 -08:00
setenv.c simplify inclusion of system header files. 2006-12-20 09:51:35 -08:00
snprintf.c Test for WIN32 instead of __MINGW32_ 2009-09-18 20:00:42 -07:00
strcasestr.c Clean up compatibility definitions. 2005-12-05 15:50:29 -08:00
strlcpy.c simplify inclusion of system header files. 2006-12-20 09:51:35 -08:00
strtoumax.c Add a compat/strtoumax.c for Solaris 8. 2007-02-19 18:20:30 -08:00
unsetenv.c simplify inclusion of system header files. 2006-12-20 09:51:35 -08:00
win32.h Make usage of windows.h lean and mean 2009-09-18 20:00:42 -07:00
win32mmap.c MSVC: Add support for building with NO_MMAP 2009-11-08 17:59:12 -08:00
winansi.c Make usage of windows.h lean and mean 2009-09-18 20:00:42 -07:00