Am 30.01.2017 um 17:01 schrieb Johannes Schindelin:

On Sat, 28 Jan 2017, René Scharfe wrote:

quoted

diff --git a/git-compat-util.h b/git-compat-util.h
index 87237b092b..66cd466eea 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h

@@ -527,6 +527,16 @@ static inline int ends_with(const char *str, const char *suffix)
 	return strip_suffix(str, suffix, &len);
 }

+#define SWAP(a, b) do {						\
+	void *_swap_a_ptr = &(a);				\
+	void *_swap_b_ptr = &(b);				\
+	unsigned char _swap_buffer[sizeof(a)];			\
+	memcpy(_swap_buffer, _swap_a_ptr, sizeof(a));		\
+	memcpy(_swap_a_ptr, _swap_b_ptr, sizeof(a) +		\
+	       BUILD_ASSERT_OR_ZERO(sizeof(a) == sizeof(b)));	\
+	memcpy(_swap_b_ptr, _swap_buffer, sizeof(a));		\
+} while (0)
+
 #if defined(NO_MMAP) || defined(USE_WIN32_MMAP)

It may seem as a matter of taste, or maybe not: I prefer this without the
_swap_a_ptr

The purpose of these pointers is certainly to avoid that the macro 
arguments are evaluated more than once.

-- Hannes