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authorLibravatar Karsten Blees <blees@dcon.de>2012-01-14 22:24:19 +0100
committerLibravatar Junio C Hamano <gitster@pobox.com>2014-06-10 13:32:59 -0700
commiteac14f8909d986a38d9eab4a7f926af41dd64a4f (patch)
treebfb6232a7c07c07defe9e8272b8879ee35cada6d /t/t5521-pull-options.sh
parentWin32: add Unicode conversion functions (diff)
downloadtgif-eac14f8909d986a38d9eab4a7f926af41dd64a4f.tar.xz
Win32: Thread-safe windows console output
Winansi.c has many static variables that are accessed and modified from the [v][f]printf / fputs functions overridden in the file. This may cause multi threaded git commands that print to the console to produce corrupted output or even crash. Additionally, winansi.c doesn't override all functions that can be used to print to the console (e.g. fwrite, write, fputc are missing), so that ANSI escapes don't work properly for some git commands (e.g. git-grep). Instead of doing ANSI emulation in just a few wrapped functions on top of the IO API, let's plug into the IO system and take advantage of the thread safety inherent to the IO system. Redirect stdout and stderr to a pipe if they point to the console. A background thread reads from the pipe, handles ANSI escape sequences and UTF-8 to UTF-16 conversion, then writes to the console. The pipe-based stdout and stderr replacements must be set to unbuffered, as MSVCRT doesn't support line buffering and fully buffered streams are inappropriate for console output. Due to the byte-oriented pipe, ANSI escape sequences and multi-byte UTF-8 sequences can no longer be expected to arrive in one piece. Replace the string-based ansi_emulate() with a simple stateful parser (this also fixes colored diff hunk headers, which were broken as of commit 2efcc977). Override isatty to return true for the pipes redirecting to the console. Exec/spawn obtain the original console handle to pass to the next process via winansi_get_osfhandle(). All other overrides are gone, the default stdio implementations work as expected with the piped stdout/stderr descriptors. Global variables are either initialized on startup (single threaded) or exclusively modified by the background thread. Threads communicate through the pipe, no further synchronization is necessary. The background thread is terminated by disonnecting the pipe after flushing the stdio and pipe buffers. This doesn't work for anonymous pipes (created via CreatePipe), as DisconnectNamedPipe only works on the read end, which discards remaining data. Thus we have to setup the pipe manually, with the write end beeing the server (opened with CreateNamedPipe) and the read end the client (opened with CreateFile). Limitations: doesn't track reopened or duped file descriptors, i.e.: - fdopen(1/2) returns fully buffered streams - dup(1/2), dup2(1/2) returns normal pipe descriptors (i.e. isatty() = false, winansi_get_osfhandle won't return the original console handle) Currently, only the git-format-patch command uses xfdopen(xdup(1)) (see "realstdout" in builtin/log.c), but works well with these limitations. Many thanks to Atsushi Nakagawa <atnak@chejz.com> for suggesting and reviewing the thread-exit-mechanism. Signed-off-by: Karsten Blees <blees@dcon.de> Signed-off-by: Stepan Kasal <kasal@ucw.cz> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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