compate/clipped-write.c: large write(2) fails on Mac OS X/XNU

Due to a bug in the Darwin kernel, write(2) calls have a maximum size
of INT_MAX bytes.

Introduce a new compat function, clipped_write(), that only writes
at most INT_MAX bytes and returns the number of bytes written, as
a substitute for write(2), and allow platforms that need this to
enable it from the build mechanism with NEEDS_CLIPPED_WRITE.

Set it for Mac OS X by default.  It may be necessary to include this
function on Windows, too.

Signed-off-by: Filipe Cabecinhas <filcab+git@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Makefile b/Makefile
index 26d333275517943c629e9600525f292d4c91d32a..0434715f0e86ec0d055c4a7fbf55d975c06b825d 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -69,6 +69,9 @@ all::
 # Define NO_MSGFMT_EXTENDED_OPTIONS if your implementation of msgfmt
 # doesn't support GNU extensions like --check and --statistics
 #
+# Define NEEDS_CLIPPED_WRITE if your write(2) cannot write more than
+# INT_MAX bytes at once (e.g. MacOS X).
+#
 # Define HAVE_PATHS_H if you have paths.h and want to use the default PATH
 # it specifies.
 #
@@ -1463,6 +1466,11 @@ ifndef NO_MSGFMT_EXTENDED_OPTIONS
        MSGFMT += --check --statistics
 endif
 
+ifdef NEEDS_CLIPPED_WRITE
+       BASIC_CFLAGS += -DNEEDS_CLIPPED_WRITE
+       COMPAT_OBJS += compat/clipped-write.o
+endif
+
 ifneq (,$(XDL_FAST_HASH))
        BASIC_CFLAGS += -DXDL_FAST_HASH
 endif

diff --git a/compat/clipped-write.c b/compat/clipped-write.c
new file mode 100644 (file)
index 0000000..b8f98ff
--- /dev/null
+++ b/compat/clipped-write.c
@@ -0,0 +1,13 @@
+#include "../git-compat-util.h"
+#undef write
+
+/*
+ * Version of write that will write at most INT_MAX bytes.
+ * Workaround a xnu bug on Mac OS X
+ */
+ssize_t clipped_write(int fildes, const void *buf, size_t nbyte)
+{
+       if (nbyte > INT_MAX)
+               nbyte = INT_MAX;
+       return write(fildes, buf, nbyte);
+}

diff --git a/config.mak.uname b/config.mak.uname
index e09af8fc13ec4c3c6fa326e8208c98be52347a10..e689a9a867e1b0aae24197ba95dac8e8d7e019e2 100644 (file)
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -95,6 +95,7 @@ ifeq ($(uname_S),Darwin)
        NO_MEMMEM = YesPlease
        USE_ST_TIMESPEC = YesPlease
        HAVE_DEV_TTY = YesPlease
+       NEEDS_CLIPPED_WRITE = YesPlease
        COMPAT_OBJS += compat/precompose_utf8.o
        BASIC_CFLAGS += -DPRECOMPOSE_UNICODE
 endif

diff --git a/git-compat-util.h b/git-compat-util.h
index b636e0dd0c2ea8284ed6f34e32c448eae433a20a..3144b8da1e0a7346739ee5acbf5865de3da7d210 100644 (file)
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -181,6 +181,11 @@ typedef unsigned long uintptr_t;
 #define probe_utf8_pathname_composition(a,b)
 #endif
 
+#ifdef NEEDS_CLIPPED_WRITE
+ssize_t clipped_write(int fildes, const void *buf, size_t nbyte);
+#define write(x,y,z) clipped_write((x),(y),(z))
+#endif
+
 #ifdef MKDIR_WO_TRAILING_SLASH
 #define mkdir(a,b) compat_mkdir_wo_trailing_slash((a),(b))
 extern int compat_mkdir_wo_trailing_slash(const char*, mode_t);