Hi Hannes,

On Mon, 30 Jan 2017, Johannes Sixt wrote:

Am 30.01.2017 um 17:01 schrieb Johannes
Schindelin:

quoted

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.

I mistook "a" being used in sizeof(a) for breaking that assumption, but of
course a is *not* evaluated in that case. It is curious, though, that an
expression like "sizeof(a++)" would not be rejected.

Further, what would SWAP(a++, b) do? Swap a and b, and *then* increment a?

Ciao,
Johannes