(verbose_)?try_malloc() to use on buf_write()

There will be more use cases for try_malloc(): see #556.

 - Reimplemented xmalloc() using try_malloc().
 - verbose_try_malloc() is just like try_malloc() but shows an out-of-memory
	 error message before returning NULL.
 - Let the compiler generate size>>1 assembly for signed types. We're not using
	 old compilers here.
 - Add proper function attributes to the new functions in memory.h

1 files changed, 19 insertions, 1 deletions

diff --git a/src/memory.h b/src/memory.h
index 05ac9359e5..bc20c0420e 100644
--- a/src/memory.h
+++ b/src/memory.h
@@ -10,6 +10,24 @@ char_u *alloc_clear(unsigned size) FUNC_ATTR_MALLOC FUNC_ATTR_ALLOC_SIZE(1);
 
 /// malloc() wrapper
 ///
+/// try_malloc() is a malloc() wrapper that tries to free some memory before
+/// trying again.
+///
+/// @see {try_to_free_memory}
+/// @param size
+/// @return pointer to allocated space. NULL if out of memory
+void *try_malloc(size_t size) FUNC_ATTR_MALLOC FUNC_ATTR_ALLOC_SIZE(1);
+
+/// try_malloc() wrapper that shows an out-of-memory error message to the user
+/// before returning NULL
+///
+/// @see {try_malloc}
+/// @param size
+/// @return pointer to allocated space. NULL if out of memory
+void *verbose_try_malloc(size_t size) FUNC_ATTR_MALLOC FUNC_ATTR_ALLOC_SIZE(1);
+
+/// malloc() wrapper that never returns NULL
+///
 /// xmalloc() succeeds or gracefully aborts when out of memory.
 /// Before aborting try to free some memory and call malloc again.
 ///
@@ -51,7 +69,7 @@ void *xmallocz(size_t size) FUNC_ATTR_MALLOC FUNC_ATTR_NONNULL_RET;
 /// @see {xmalloc}
 /// @param data Pointer to the data that will be copied
 /// @param len number of bytes that will be copied
-void *xmemdupz(const void *data, size_t len);
+void *xmemdupz(const void *data, size_t len) FUNC_ATTR_NONNULL_RET;
 
 /// strdup() wrapper
 ///