Re: [PATCH 3/4] Introduce "abstract class" to make _locate_element() more independant of diff_rename_dst.
From: Jonathan Nieder <hidden>
Date: 2016-06-15 22:49:58
Yann Dirson wrote:
quoted hunk ↗ jump to hunk
--- a/diffcore-rename.c +++ b/diffcore-rename.c@@ -6,12 +6,16 @@ #include "diffcore.h" #include "hash.h" + +/* "Abstract class" for lists of filespecs */ +struct dst_obj { + struct diff_filespec *two; +}; #define locate_element(list,elem,insert_ok) \ _locate_element(elem, &list##_nr, &list##_alloc, \ sizeof(*list), insert_ok) -/* Table of rename/copy destinations */ - +/* Table of rename/copy destinations, "subclass" of dst_obj */ static struct diff_rename_dst { struct diff_filespec *two;
Nit: language lawyers might be happier with:
struct dst_obj {
struct diff_filespec *spec
};
struct diff_rename_dst {
struct dst_obj two;
...
};
or
typedef struct diff_filespec *dst_obj;
struct diff_rename_dst {
dst_obj two;
...
};
or
struct diff_rename_dst {
struct diff_filespec *two;
...
};
...
struct diff_filespec **dst = (const char *) rename_dst + next * elem_size;
to avoid violating strict aliasing rules.
Meanwhile, something like
#define container_of(ptr, type, member) \
((type *)((char *) ptr - offsetof(type, member)))
can be useful for making the meaning more obvious when downcasting.