[PATCH 2/9] git-compat-util: add fallbacks for unlocked stdio

From: Jeff King <peff@peff.net>
Date: Apr 16, 2015, 08:48 UTC
Message-ID: <20150416084844.GB17938@peff.net>
In-Reply-To: <20150416084733.GA17811@peff.net>

POSIX.1-2001 specifies some functions for optimizing the locking out of tight getc() loops. Not all systems are POSIX, though, and even not all POSIX systems are required to implement these functions. We can check for the feature-test macro to see if they are available, and if not, provide a noop implementation.

There's no Makefile knob here, because we should just detect this automatically. If there are very bizarre systems, we may need to add one, but it's not clear yet in which direction:

  1. If a system defines _POSIX_THREAD_SAFE_FUNCTIONS but
     these functions are missing or broken, we would want a
     knob to manually turn them off.

  2. If a system has these functions but does not define
     _POSIX_THREAD_SAFE_FUNCTIONS, we would want a knob to
     manually turn them on.

We can add such a knob when we find a real-world system that matches this.

Signed-off-by: Jeff King <peff@peff.net>
---
 git-compat-util.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/git-compat-util.h b/git-compat-util.h
index bc8fc8c..685a0a4 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -883,4 +883,10 @@ struct tm *git_gmtime_r(const time_t *, struct tm *);
 # define SHELL_PATH "/bin/sh"
 #endif
 
+#ifndef _POSIX_THREAD_SAFE_FUNCTIONS
+#define flockfile(fh)
+#define funlockfile(fh)
+#define getc_unlocked(fh) getc(fh)
+#endif
+
 #endif

-- 
2.4.0.rc2.384.g7297a4a