[Tarantool-patches] [PATCH 1/2] errinj: introduce delayed injection

[Nikita Pettik <korablev@tarantool.org>]

With new macro ERROR_INJECT_DELAYED it is possible to delay error
injection by DELAY parameter: injection will be set only after DELAY
times the path is executed. For instance:

void
foo(int i)
{
	/* 2 is delay counter. */
	ERROR_INJECT_DELAYED(ERRINJ_FOO, 2, {
		 printf("Error injection on %d cycle!\n", i);
		});
}

void
boo(void)
{
	for (int i = 0; i < 10; ++i)
		foo(i);
}

The result is "Error injection on 2 cycle!". This type of error
injection can turn out to be useful to set injection in the middle of
query processing. Imagine following scenario:

void
foo(void)
{
	int *fds[10];
	for (int i = 0; i < 10; ++i) {
		fds[i] = malloc(sizeof(int));
		if (fds[i] == NULL)
			goto cleanup;
	}
cleanup:
	free(fds[0]);
}

"cleanup" section obviously contains error and leads to memory leak.
But using means of casual error injection without delay such situation
can't be detected: OOM can be set only for first cycle iteration and in
this particular case no leaks take place.
---
 src/errinj.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/errinj.h b/src/errinj.h
index 2cb090b68..990f4921d 100644
--- a/src/errinj.h
+++ b/src/errinj.h
@@ -149,6 +149,7 @@ errinj_foreach(errinj_cb cb, void *cb_ctx);
 #ifdef NDEBUG
 #  define ERROR_INJECT(ID, CODE)
 #  define errinj(ID, TYPE) ((struct errinj *) NULL)
+#  define ERROR_INJECT_DELAYED(ID, DELAY, CODE)
 #else
 #  /* Returns the error injection by id */
 #  define errinj(ID, TYPE) \
@@ -162,6 +163,14 @@ errinj_foreach(errinj_cb cb, void *cb_ctx);
 		if (errinj(ID, ERRINJ_BOOL)->bparam) \
 			CODE; \
 	} while (0)
+#  define ERROR_INJECT_DELAYED(ID, DELAY, CODE) \
+	do { \
+		static int _DELAY##ID = DELAY; \
+		if (errinj(ID, ERRINJ_BOOL)->bparam) { \
+			if (_DELAY##ID-- == 0) \
+				CODE; \
+		} \
+	} while (0)
 #endif
 
 #define ERROR_INJECT_RETURN(ID) ERROR_INJECT(ID, return -1)
-- 
2.17.1