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lib: add macro that performs explicit static casts when using a C++ compiler

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C++ doesn't support implicit casts from void pointers like C
does. And the libfrr headers have some bits of code that rely on
implicit casts in order to work. To solve this problem, add a new
"static_cast" macro that performs explicit static casts when a C++
compiler is being used, or do nothing otherwise.

NOTE: since macros are only evaluated when they are used, there
might be other macros from libfrr that will need to use "static_cast"
as well. If a header is successfully compiled using a C++ compiler,
there's no guarantee that its macros are compatible with C++. We'll
only know about such macros when they are used by C++ code, then
we'll need to adapt them one by one in the future.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>
This commit is contained in:
Renato Westphal 2019-02-11 16:04:26 -02:00
parent c139972c0f
commit 343cd13e17
2 changed files with 12 additions and 2 deletions
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5
lib/linklist.h
View File

@ -295,7 +295,8 @@ extern void list_add_list(struct list *list, struct list *add);
#define ALL_LIST_ELEMENTS(list, node, nextnode, data) \ #define ALL_LIST_ELEMENTS(list, node, nextnode, data) \
(node) = listhead(list), ((data) = NULL); \ (node) = listhead(list), ((data) = NULL); \
(node) != NULL \ (node) != NULL \
&& ((data) = listgetdata(node), (nextnode) = node->next, 1); \ && ((data) = static_cast(data, listgetdata(node)), \
(nextnode) = node->next, 1); \
(node) = (nextnode), ((data) = NULL) (node) = (nextnode), ((data) = NULL)
/* read-only list iteration macro. /* read-only list iteration macro.
@ -306,7 +307,7 @@ extern void list_add_list(struct list *list, struct list *add);
*/ */
#define ALL_LIST_ELEMENTS_RO(list, node, data) \ #define ALL_LIST_ELEMENTS_RO(list, node, data) \
(node) = listhead(list), ((data) = NULL); \ (node) = listhead(list), ((data) = NULL); \
(node) != NULL && ((data) = listgetdata(node), 1); \ (node) != NULL && ((data) = static_cast(data, listgetdata(node)), 1); \
(node) = listnextnode(node), ((data) = NULL) (node) = listnextnode(node), ((data) = NULL)
/* these *do not* cleanup list nodes and referenced data, as the functions /* these *do not* cleanup list nodes and referenced data, as the functions

9
lib/zebra.h
View File

@ -232,6 +232,15 @@ typedef unsigned char uint8_t;
#include "zassert.h" #include "zassert.h"
/*
* Add explicit static cast only when using a C++ compiler.
*/
#ifdef __cplusplus
#define static_cast(l, r) static_cast<decltype(l)>((r))
#else
#define static_cast(l, r) (r)
#endif
#ifndef HAVE_STRLCAT #ifndef HAVE_STRLCAT
size_t strlcat(char *__restrict dest, size_t strlcat(char *__restrict dest,
const char *__restrict src, size_t destsize); const char *__restrict src, size_t destsize);