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Merge branch 'js/mingw-o-append'

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Among the three codepaths we use O_APPEND to open a file for
appending, one used for writing GIT_TRACE output requires O_APPEND
implementation that behaves sensibly when multiple processes are
writing to the same file.  POSIX emulation used in the Windows port
has been updated to improve in this area.

* js/mingw-o-append:
  mingw: enable atomic O_APPEND
This commit is contained in:
Junio C Hamano 2018-08-20 11:33:52 -07:00
parent 0c54cdaf65 d641097589
commit d18d09bb81
1 changed files with 39 additions and 2 deletions
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41
compat/mingw.c
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@ -341,12 +341,44 @@ int mingw_mkdir(const char *path, int mode)
return ret;
}
static int mingw_open_append(wchar_t const *wfilename, int oflags, ...)
{
HANDLE handle;
int fd;
DWORD create = (oflags & O_CREAT) ? OPEN_ALWAYS : OPEN_EXISTING;
/* only these flags are supported */
if ((oflags & ~O_CREAT) != (O_WRONLY | O_APPEND))
return errno = ENOSYS, -1;
/*
* FILE_SHARE_WRITE is required to permit child processes
* to append to the file.
*/
handle = CreateFileW(wfilename, FILE_APPEND_DATA,
FILE_SHARE_WRITE | FILE_SHARE_READ,
NULL, create, FILE_ATTRIBUTE_NORMAL, NULL);
if (handle == INVALID_HANDLE_VALUE)
return errno = err_win_to_posix(GetLastError()), -1;
/*
* No O_APPEND here, because the CRT uses it only to reset the
* file pointer to EOF on write(); but that is not necessary
* for a file created with FILE_APPEND_DATA.
*/
fd = _open_osfhandle((intptr_t)handle, O_BINARY);
if (fd < 0)
CloseHandle(handle);
return fd;
}
int mingw_open (const char *filename, int oflags, ...)
{
typedef int (*open_fn_t)(wchar_t const *wfilename, int oflags, ...);
va_list args;
unsigned mode;
int fd;
wchar_t wfilename[MAX_PATH];
open_fn_t open_fn;
va_start(args, oflags);
mode = va_arg(args, int);
@ -355,9 +387,14 @@ int mingw_open (const char *filename, int oflags, ...)
if (filename && !strcmp(filename, "/dev/null"))
filename = "nul";
if (oflags & O_APPEND)
open_fn = mingw_open_append;
else
open_fn = _wopen;
if (xutftowcs_path(wfilename, filename) < 0)
return -1;
fd = _wopen(wfilename, oflags, mode);
fd = open_fn(wfilename, oflags, mode);
if (fd < 0 && (oflags & O_ACCMODE) != O_RDONLY && errno == EACCES) {
DWORD attrs = GetFileAttributesW(wfilename);
@ -375,7 +412,7 @@ int mingw_open (const char *filename, int oflags, ...)
* CREATE_ALWAYS flag of CreateFile()).
*/
if (fd < 0 && errno == EACCES)
fd = _wopen(wfilename, oflags & ~O_CREAT, mode);
fd = open_fn(wfilename, oflags & ~O_CREAT, mode);
if (fd >= 0 && set_hidden_flag(wfilename, 1))
warning("could not mark '%s' as hidden.", filename);
}