sanity: Get rid of sanitize_ignore()

It's probably nicer to avoid evaluating expensive arguments when not
sanitizing, rather than relying on the optimizer to clean them up.

src/alloc.c

@@ -317,8 +317,8 @@ void *varena_realloc(struct varena *varena, void *ptr, size_t old_count, size_t
 		return NULL;
 	}
 
-	size_t new_exact_size = varena_exact_size(varena, new_count);
-	size_t old_exact_size = varena_exact_size(varena, old_count);
+	_maybe_unused size_t new_exact_size = varena_exact_size(varena, new_count);
+	_maybe_unused size_t old_exact_size = varena_exact_size(varena, old_count);
 
 	if (new_arena == old_arena) {
 		if (new_count < old_count) {

src/sanity.h

@@ -20,11 +20,6 @@
 #define SANITIZE_CALL__(macro, ptr, size, ...) \
 	macro(ptr, size)
 
-/**
- * Squelch unused variable warnings when not sanitizing.
- */
-#define sanitize_ignore(ptr, size) ((void)(ptr), (void)(size))
-
 #if __SANITIZE_ADDRESS__
 #  include <sanitizer/asan_interface.h>
 
@@ -43,8 +38,8 @@
 #define sanitize_free(...) SANITIZE_CALL(__asan_poison_memory_region, __VA_ARGS__)
 
 #else
-#  define sanitize_alloc(...) SANITIZE_CALL(sanitize_ignore, __VA_ARGS__)
-#  define sanitize_free(...) SANITIZE_CALL(sanitize_ignore, __VA_ARGS__)
+#  define sanitize_alloc(...) ((void)0)
+#  define sanitize_free(...) ((void)0)
 #endif
 
 #if __SANITIZE_MEMORY__
@@ -65,8 +60,8 @@
 #define sanitize_uninit(...) SANITIZE_CALL(__msan_allocated_memory, __VA_ARGS__)
 
 #else
-#  define sanitize_init(...) SANITIZE_CALL(sanitize_ignore, __VA_ARGS__)
-#  define sanitize_uninit(...) SANITIZE_CALL(sanitize_ignore, __VA_ARGS__)
+#  define sanitize_init(...) ((void)0)
+#  define sanitize_uninit(...) ((void)0)
 #endif
 
 /**