Merge branch 'strict-aliasing' into 'master'

fix strict aliasing problems

See merge request !962

NEWS

@@ -9,6 +9,7 @@ Bugfixes
 --------
 - cache: missing filesystem support for pre-allocation is no longer fatal (#549)
 - lua: policy.rpz() no longer watches the file when watch is set to false (!954)
+- fix a strict aliasing problem that might've lead to "miscompilation" (!962)
 
 
 Knot Resolver 5.0.1 (2020-02-05)

lib/generic/array.h

@@ -64,7 +64,7 @@ static inline size_t array_next_count(size_t want)
 }
 
 /** @internal Incremental memory reservation */
-static inline int array_std_reserve(void *baton, char **mem, size_t elm_size, size_t want, size_t *have)
+static inline int array_std_reserve(void *baton, void **mem, size_t elm_size, size_t want, size_t *have)
 {
 	if (*have >= want) {
 		return 0;
@@ -110,7 +110,7 @@ static inline void array_std_free(void *baton, void *p)
  * Mempool usage: pass kr_memreserve and a knot_mm_t* .
  * @return 0 if success, <0 on failure */
 #define array_reserve_mm(array, n, reserve, baton) \
-	(reserve)((baton), (char **) &(array).at, sizeof((array).at[0]), (n), &(array).cap)
+	(reserve)((baton), (void **) &(array).at, sizeof((array).at[0]), (n), &(array).cap)
 
 /**
  * Push value at the end of the array, resize it if necessary.

lib/generic/test_array.c

@@ -46,7 +46,7 @@ static void test_array(void **state)
 }
 
 /** Reservation through tracked memory allocator. */
-static int test_reserve(void *baton, char **mem, size_t elm_size, size_t want, size_t *have)
+static int test_reserve(void *baton, void **mem, size_t elm_size, size_t want, size_t *have)
 {
 	if (want > *have) {
 		void *new_mem = mm_alloc(baton, elm_size * want);
@@ -62,7 +62,7 @@ static int test_reserve(void *baton, char **mem, size_t elm_size, size_t want, s
 }
 
 /** Reservation through fake memory allocator. */
-static int fake_reserve(void *baton, char **mem, size_t elm_size, size_t want, size_t *have)
+static int fake_reserve(void *baton, void **mem, size_t elm_size, size_t want, size_t *have)
 {
 	return -1;
 }

lib/utils.c

@@ -213,7 +213,7 @@ char* kr_strcatdup(unsigned n, ...)
 	return result;
 }
 
-int kr_memreserve(void *baton, char **mem, size_t elm_size, size_t want, size_t *have)
+int kr_memreserve(void *baton, void **mem, size_t elm_size, size_t want, size_t *have)
 {
     if (*have >= want) {
         return 0;

lib/utils.h

@@ -261,7 +261,7 @@ static inline bool kr_rand_coin(unsigned int nomin, unsigned int denomin)
 
 /** Memory reservation routine for knot_mm_t */
 KR_EXPORT
-int kr_memreserve(void *baton, char **mem, size_t elm_size, size_t want, size_t *have);
+int kr_memreserve(void *baton, void **mem, size_t elm_size, size_t want, size_t *have);
 
 /** @internal Fast packet reset. */
 KR_EXPORT

meson.build

@@ -118,6 +118,14 @@ add_project_arguments(
   '-Werror=implicit-function-declaration', # Probably messed up includes; implicit functions are evil!
   '-fvisibility=hidden',
   '-DHAVE_ASPRINTF=' + have_asprintf.to_int().to_string(),
+
+  # libuv handles have aliasing problems; see:
+  # https://github.com/libuv/libuv/pull/2588/files#diff-04c6e90faac2675aa89e2176d2eec7d8
+  # https://github.com/libuv/libuv/issues/1230#issuecomment-569030944
+  # Performance impact in our case seems OK:
+  # https://gitlab.labs.nic.cz/knot/knot-resolver/-/merge_requests/962#note_147407
+  '-fno-strict-aliasing',
+
   language: 'c',
 )