Using cygwin with cygwin.dll before 1.5.22 the system call pread() is buggy.
This patch introduces NO_PREAD. If NO_MMAP is not set and NO_PREAD is set
git uses real mmap instead of pread.
Signed-off-by: Stefan-W. Hahn <stefan.hahn@xxxxxxxxx>
---
I made a patch for this problem replacing pread().
Makefile | 9 +++++++++
compat/pread.c | 16 ++++++++++++++++
git-compat-util.h | 5 +++++
3 files changed, 30 insertions(+), 0 deletions(-)
diff --git a/Makefile b/Makefile
index 180e1e0..4f928fd 100644
--- a/Makefile
+++ b/Makefile
@@ -69,6 +69,10 @@ all:
#
# Define NO_MMAP if you want to avoid mmap.
#
+# Define NO_PREAD if you have a problem with pread() system call (i.e.
+# cygwin.dll before v1.5.22). This needs NO_MMAP not to be set, because pread()
+# is emulated using mmap.
+#
# Define NO_FAST_WORKING_DIRECTORY if accessing objects in pack files is
# generally faster on your platform than accessing the working directory.
#
@@ -521,6 +525,11 @@ endif
ifdef NO_MMAP
COMPAT_CFLAGS += -DNO_MMAP
COMPAT_OBJS += compat/mmap.o
+else
+ifdef NO_PREAD
+ COMPAT_CFLAGS += -DNO_PREAD
+ COMPAT_OBJS += compat/pread.o
+endif
endif
ifdef NO_FAST_WORKING_DIRECTORY
BASIC_CFLAGS += -DNO_FAST_WORKING_DIRECTORY
diff --git a/compat/pread.c b/compat/pread.c
new file mode 100644
index 0000000..23e775d
--- /dev/null
+++ b/compat/pread.c
@@ -0,0 +1,16 @@
+#include "../git-compat-util.h"
+
+ssize_t git_pread(int fd,void *buf,size_t count,off_t offset)
+{
+ unsigned pg_offset = offset % getpagesize();
+ unsigned char *map;
+
+ map = mmap(NULL, count + pg_offset, PROT_READ, MAP_PRIVATE,
+ fd, offset - pg_offset);
+ if (map == MAP_FAILED)
+ return -1;
+
+ memcpy(buf, map + pg_offset, count);
+ munmap(map, count + pg_offset);
+ return count;
+}
diff --git a/git-compat-util.h b/git-compat-util.h
index 5d9eb26..413e7e8 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -96,6 +96,11 @@ extern int git_munmap(void *start, size_t length);
#include <sys/mman.h>
+#ifdef NO_PREAD
+#define pread git_pread
+extern ssize_t git_pread(int fd,void *buf,size_t count,off_t offset);
+#endif
+
#endif /* NO_MMAP */
#ifdef NO_SETENV
--
1.5.0.rc0.g244a7
-
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